CLB-09061; No. of pages: 4; 4C: Clinical Biochemistry xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem
Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis Hong-Yuan Shen a,1, Wei Gao b,1, Juan-Juan Cheng a, Shi-Di Zhao a, Yi Sun c, Zhi-Jun Han a,⁎, Jun Hua a,⁎ a b c
Department of Laboratory Medicine, Wuxi Second People's Hospital of Nanjing Medical University, Wuxi, PR China Department of Neurology, Wuxi New District Phoenix Hospital, Wuxi, PR China Department of Laboratory Diagnosis, Changhai Hospital, Second Military Medical University, Shanghai, PR China
a r t i c l e
i n f o
Article history: Received 6 May 2015 Received in revised form 23 June 2015 Accepted 24 June 2015 Available online xxxx Keywords: Meningitis PCT CSF Biomarker
a b s t r a c t Objective: To compare the clinical utility of serum and cerebrospinal fluid (CSF) procalcitonin (PCT) for the diagnosis of bacterial meningitis (BM) among patients with suspected meningitis. Methods: Patients with meningitis-like symptoms (n = 120), admitted to the Second People's Hospital of Wuxi or the Changhai Hospital of Shanghai between January 2011 and December 2013, were prospectively and consecutively enrolled in this study. BM was finally diagnosed by CSF culture, Gram staining, quantitative polymerase chain reaction (qPCR), and treatment response. The diagnostic accuracy of the serum and CSF PCT was assessed by receiver operator characteristic (ROC) curve analysis. The relationship between CSF and serum PCT levels as well as the CSF leukocyte count and protein level was analyzed by Spearman's correlation analysis. Results: PCT level in both the serum and CSF was significantly increased in the BM patients. The area under ROC curve of serum PCT for the diagnosis of BM was 0.96 (95% confidence interval (CI): 0.93–1.00), significantly higher than that of CSF PCT (0.90, 95% CI: 0.83–0.96). Using 0.88 ng/mL as the threshold, the diagnostic sensitivity, specificity, and accuracy of serum PCT for the diagnosis of BM were 0.87 (95% CI, 0.73–0.95), 1.00 (95% CI, 0.95–1.00), and 95%, respectively. The serum PCT level was positively correlated with the CSF PCT level, leukocyte count, and protein level. Conclusion: Both the serum and CSF PCT had a high diagnostic value for BM among suspected meningitis patients, and serum PCT demonstrated a superior diagnostic value compared to CSF PCT. © 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
1. Introduction Bacterial meningitis (BM) remains a common infectious disease with high mortality and constitutes a major medical concern to public health worldwide [1–3]. To a large extent, clinical manifestations among BM and viral meningitis, tuberculous meningitis, and fungal meningitis are similar; however, different treatment approaches are required for different pathogens. Thus, an early and accurate differential diagnosis is crucial [4,5]. Generally, the diagnosis of BM relies on microbiological tests and laboratory findings. Identifying of pathogens by cerebrospinal fluid (CSF) bacterial culture and Gram staining is highly specific; however, the sensitivity of bacterial culture and staining techniques is low as it has been reported that nearly half of BM patients had negative microbiological findings [6,7]. In addition, microbiological examination is time consuming, which makes an early diagnosis impossible. Analysis of leukocyte count and protein level in CSF is an alternative method for diagnosing BM, although the sensitivity and specificity ⁎ Corresponding authors at: Department of Laboratory Medicine, Wuxi Second People's Hospital of Nanjing Medical University, Wuxi, PR China. E-mail addresses: [email protected] (Z.-J. Han), [email protected] (J. Hua). 1 Both authors contributed equally to this work.
are not high enough to differentiate BM from viral meningitis, tuberculous meningitis, or fungal meningitis [7,8]. Therefore, it is necessary to identify more sensitive and specific biomarkers for the diagnosis of BM. In recent decades, procalcitonin (PCT), a polypeptide of 116 amino acids, has been reported to be an effective biomarker for bacterial infection [9,10]. A meta-analysis showed that the sensitivity and specificity of PCT for differentiating bacterial from viral infections were 0.92 and 0.86, respectively [11]. The PCT concentration in both serum and CSF of BM patients is increased, and both can serve as diagnostic markers for BM detection [12–15]. However, it is remains unknown whether serum or CSF PCT is better for the diagnosis of BM. Therefore, the aim of the present study was to compare the diagnostic accuracy between serum and CSF PCT determination in parallel. We focused our investigations on whether serum and CSF PCT had a high diagnostic value for BM among suspected meningitis patients. 2. Material and methods 2.1. Participants A total of 150 patients with meningitis-like manifestations, who were admitted to the Second People's Hospital of Wuxi or the Changhai
http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017 0009-9120/© 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
2
H.-Y. Shen et al. / Clinical Biochemistry xxx (2015) xxx–xxx
Hospital of Shanghai between January 2011 and December 2013, were prospectively and consecutively enrolled in this study. The inclusion criteria were as follows: 1) patients with two of the following symptoms or signs: fever, confusion, headache, or nuchal rigidity; 2) older than 18 years old; 3) no determination of a meningitis pathogen on admission; and 4) CSF leukocyte count greater than 5 × 106/L [16]. Patients who were infected with bacteria and received antibiotic therapy during the past two weeks were excluded. The present study was approved by the Ethics Committees of the Second People's Hospital of Wuxi and the Changhai Hospital of Shanghai. Written informed consent was obtained from all patients included in this study. 2.2. PCT test methods The serum and CSF samples were drawn within 8 h after admission. After completing routine bacterial and chemical analyses (e.g., CSF leukocyte count, protein level determination, and bacterial culture), the serum and CSF samples were stored immediately at − 80 °C. In June 2014, all the serum and CSF samples were subjected to PCT concentration determination by immunolumino-metric assay (LUMItest PCT, BRAHMS Diagnostica, Berlin, Germany). The laboratory technicians were blinded to the clinical information of the subjects. 2.3. Diagnosis of BM Leukocyte count and protein level were determined in the CSF samples from all admitted subjects. In addition, the blood and CSF samples were subjected to bacterial culture and Gram staining. Finally, the CSF samples were tested for viral infection, including CMV, ECHO, and HSV, by quantitative polymerase chain reaction (qPCR) to detect viral infection. Patients with positive CSF bacterial culture or Gram staining, but negative qPCR test, were diagnosed as BM, and antibiotic therapy was initiated immediately. The patients who tested positive for viral infection according to the qPCR test, but had negative CSF bacterial culture and Gram staining, were diagnosed as viral meningitis. For the cases with negative bacterial culture, Gram staining and qPCR, experimental therapy with antibiotics was introduced and the outcomes of the patients were documented [17]. The final diagnosis was made by two experienced physicians using the CSF laboratory findings and treatment response. 2.4. Statistical analysis For continuous variables, Mann–Whitney U test or Student's t-test was used to assess whether the differences had statistical significance. For categorical variables, χ2 test was used. Spearman's rank correlation coefficient was employed to analyze the relationship between two continuous variables. All continuous variables were reported as median (interquartile) or mean (SD) values. The diagnostic accuracy of PCT for BM was analyzed by receiver operator characteristic (ROC) curve analysis. The cut-off value for the PCT level was established by seeking the maximum accuracy (the proportion of true positive to true negative results). The areas under ROC curve (AUCs) were compared by the method developed by DeLong et al. [18]. P value of 0.05 or less was considered statistically significant. All tests were two-sided, and all statistical analyses were performed using SPSS version 17.0 (SPSS Inc., Chicago, IL, USA) and SigmaPlot 11.0 for Windows. 3. Results 3.1. Demographic and clinical characteristics of the subjects Of the 150 patients who were initially included in this study, 13 were returning patients and 17 had used antibiotics prior to admission. Finally, 120 meningitis patients were eligible for final analysis. All patients
were given an initial and a final diagnoses. Of these subjects, 30 who had a positive CSF or blood bacterial culture or Gram staining, but a negative PCR viral infection test, were initially diagnosed as BM. A total of 59 patients were categorized into the non-BM group because of positive PCR finding and negative CSF bacterial culture or Gram staining. For the remaining subjects, antibiotic therapy was initiated and the responses to the therapy were monitored. The final diagnosis was based on the patients' CSF leukocyte count, protein and glucose determination, as well as their responses to antibiotic therapy. Conclusively, 45 subjects were categorized into BM and 75 were categorized into the non-BM group. The clinical characteristics at baseline are shown in Table 1. Among the 75 non-BM patients, 18 were diagnosed as Coxsackie virus-induced meningitis, 17 were infected with the ECHO virus, 14 were infected with the herpes virus, 5 were infected with the EB virus, 3 were infected with the varicella zoster virus, 2 were infected with the paramyxovirus, and 16 were infected with an unknown virus. Among the BM group, 12 were infected with Streptococcus pneumoniae, 10 with Diplococcus intracellularis, 8 with Staphylococcus aureus, and 15 with unknown bacteria. 3.2. Increased serum and CSF PCT levels in the bacterial meningitis patients As shown in Fig. 1, the median serum concentration of PCT in the BM and non-BM patients was 4.22 ng/mL and 0.41 ng/mL, respectively. In addition, the CSF PCT concentration in the BM and non-BM patients was 1.88 ng/mL and 0.34 ng/mL, respectively. Both the serum and CSF PCT concentrations in the BM patients were significantly higher than those of the non-BM patients (P b 0.01 for both). 3.3. Relationship between the CSF and serum PCT levels in the BM and non-BM patients As shown in Fig. 2, the serum PCT level was positively correlated with the CSF PCT level among all meningitis patients, resulting in a correlation coefficient (R) of 0.64 (P b 0.01). We further analyzed the relationship between the serum and CSF PCT levels in the BM and non-BM patients, respectively. A significant positive correlation between the serum and CSF PCT levels (R = 0.69, P b 0.01) was observed in the BM patients but not in the non-BM patients. In addition, we also analyzed the relationships between the PCT level and the CSF leukocyte count as well as the CSF protein level. The serum PCT level was positively correlated with the CSF leukocyte count (R = 0.36, P = 0.02) and with the protein level (R = 0.39, P = 0.01) in the BM patients but not in the non-BM patients. 3.4. Diagnostic accuracy of the serum and CSF PCT levels for BM patients Fig. 3 shows the ROC curve of the serum and CSF PCT for the diagnosis of BM. The AUC for serum and CSF PCT was 0.96 (95% CI: 0.93–1.00) Table 1 Demographic and clinical characteristics of the subjects.
Number of patients Age (years) Gender (male/female) Clinical signs or symptoms Median period between symptom onset and admission (h) Fever (yes/no) Headache (yes/no) Nuchal rigidity (yes/no) Confusion (yes/no) CSF laboratory findings Leukocyte count (106/L) Protein (g/L)
BM
Non-BM
P
45 50 ± 18 30/15
75 47 ± 19 55/20
– 0.34 0.53
43 (25, 52)
43 (30, 54)
0.26
45/0 45/0 44/1 2/43
60/15 75/0 70/5 1/74
b0.01 1.00 0.41 0.55
3800 (620, 7500) 0.68 (0.40, 0.94)
280 (58, 500) b0.01 0.39 (0.25, 0.56) b0.01
Note: Values are the median and quartile, where appropriate.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
H.-Y. Shen et al. / Clinical Biochemistry xxx (2015) xxx–xxx
3
Fig. 1. Comparison of the serum and CSF PCT levels between the BM and non-BM patients. Note: Horizontal bars in the plots represent the mean values.
and 0.90 (95% CI: 0.83–0.96), respectively. The AUC for serum PCT was significantly higher than that for CSF PCT (P = 0.03), indicating that the serum PCT exhibits a significantly higher diagnostic accuracy than that of the CSF PCT. Table 2 shows the diagnostic sensitivity, specificity, and accuracy at a prespecified threshold (0.5 ng/mL) as well as the calculated threshold with maximum diagnostic accuracy. At the threshold of 0.88 ng/mL, the serum PCT showed the highest diagnostic accuracy (95.0%), implying that only 6 of the 120 meningitis patients were misdiagnosed. The highest diagnostic accuracy for CSF PCT was 83.3%, when a threshold of 0.74 ng/mL was selected. 4. Discussion The purpose of this study was to determine relative efficiency of serum and CSF PCT for diagnosis of BM. We found that PCT level in both serum and CSF of BM patients was significantly higher than that of non-BM patients. Our findings were as expected [14], since PCT is a well-recognized marker for bacterial infection [12,13,19,20]. Thus, the results from this study corroborate that PCT in serum and CSF is a potential diagnostic marker for BM. Previously, two studies have evaluated the diagnostic accuracy of both serum and CSF PCT in the same cohorts [15,21]; however, the diagnostic accuracy of serum and CSF PCT was not compared. To the best of our knowledge, this study was the first one to compare the diagnostic accuracy of two PCTs in a head-to-head manner, thus eliminating potential variations at different settings. Unlike sensitivity and specificity, which can be greatly affected by the threshold chosen, the AUC is a global parameter that estimates the diagnostic accuracy of an index test [22]. We assessed the diagnostic
Fig. 2. Correlations between the serum and CSF PCT levels in all meningitis patients (BM and non-BM). Note: Data were analyzed using the Spearman's correlation.
accuracy of both serum and CSF PCT by ROC curve analysis. A significantly higher AUC was established using serum PCT. Therefore, we concluded that the overall diagnostic accuracy of serum PCT was superior to CSF PCT in this cohort. Of note, the diagnostic accuracy of serum PCT was 95% at cut-off of 0.88 ng/mL, implying that 95% of patients with suspected meningitis can be correctly differentiated. At this cut-off value, the diagnostic specificity was 100%, implying that a patient without BM is very unlikely to have serum PCT level higher than 0.88 ng/mL. Our data suggest that the serum PCT could be a reliable marker to distinguish BM from viral meningitis. A positive correlation between the serum and CSF PCT levels was observed in our study, and this finding has not been reported previously [15,21]. Such correlation may suggest that CSF PCT may originate from serum, since the serum PCT level was higher than that of the CSF PCT level. During the pathogenic process of meningitis, the blood–brain barrier is damaged by the inflammatory response, and PCT in the blood is able to enter into the CSF. This process could explain why CSF PCT was of high diagnostic accuracy for BM. We also found that the serum PCT level was significantly and positively correlated with the CSF leukocyte count and protein level. It is well established that the CSF leukocyte count and protein level are effective indices for the differential diagnosis of meningitis. Therefore, the detection of serum PCT is a valuable addition to CSF leukocyte count and protein level determination; in addition, it saves time and makes an early and accurate diagnosis of BM possible. As the present study was limited by its small sample size, we were unable to use rigorous statistical models such as net reclassification or integrated discrimination improvement [23] to determine whether serum PCT can improve the diagnostic accuracy of CSF leukocyte count and protein level, or the converse is true. One strength of the present study should be noted. To ensure that the detected BM prevalence reflected the clinical reality [24], all the subjects in the present study were consecutively enrolled. That is why we
Fig. 3. ROC curves of the serum and CSF PCT for the diagnosis of BM.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
4
H.-Y. Shen et al. / Clinical Biochemistry xxx (2015) xxx–xxx
Table 2 Comparison of diagnostic efficiency between serum and CSF PCT at different thresholds.
Serum PCT CSF PCT
Cut-off value
Sensitivity (95% CI)
Specificity (95% CI)
Accuracy (%)
0.50 ng/mL 0.88 ng/mL 0.50 ng/mL 0.74 ng/mL
0.98 (0.88–1.00) 0.87 (0.73–0.95) 0.82 (0.68–0.92) 0.69 (0.53–0.82)
0.65 (0.53–0.76) 1.00 (0.95–1.00) 0.81 (0.71–0.89) 1.00 (0.95–1.00)
77.5 95.0 81.7 88.3
did not exclude the subjects who did not have identifiable microbiological findings from the final analysis. As reported, only 70%–85% of BM patients are positive for bacterial culture, and the sensitivity of qPCR for viral meningitis is about 90% [17], indicating that the final diagnosis of some BM and non-BM patients must be based on the clinical symptoms or signs, CSF laboratory findings and antibiotic treatment responses. In summary, we found that both serum and CSF PCT had high diagnostic value for BM among suspected meningitis patients. In addition, serum PCT exhibited a superior diagnostic value compared to CSF PCT. Therefore, we recommend that serum PCT should be the first choice for diagnosing BM. Disclosures The authors declare no conflict of interest. Acknowledgments This work was supported by a grant from the National Natural Science Foundation of China (no. 81301503). References [1] Castelblanco RL, Lee M, Hasbun R. Epidemiology of bacterial meningitis in the USA from 1997 to 2010: a population-based observational study. Lancet Infect Dis 2014;14:813–9. [2] Snaebjarnardottir K, Erlendsdottir H, Reynisson IK, Kristinsson K, Halldorsdottir S, Hardardottir H, et al. Bacterial meningitis in children in Iceland, 1975–2010: a nationwide epidemiological study. Scand J Infect Dis 2013;45:819–24. [3] Stockmann C, Ampofo K, Byington CL, Filloux F, Hersh AL, Blaschke AJ, et al. Pneumococcal meningitis in children: epidemiology, serotypes, and outcomes from 1997– 2010 in Utah. Pediatrics 2013;132:421–8. [4] Brouwer MC, Thwaites GE, Tunkel AR, Van De Beek D. Dilemmas in the diagnosis of acute community-acquired bacterial meningitis. Lancet 2012;380:1684–91.
[5] Brouwer MC, Tunkel AR, van de Beek D. Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis. Clin Microbiol Rev 2010;23:467–92. [6] Yadhav Ml K. Study of bacterial meningitis in children below 5 years with comparative evaluation of gram staining, culture and bacterial antigen detection. J Clin Diagn Res 2014;8:DC04–6. [7] Spanos A, Harrell Jr FE, Durack DT. Differential diagnosis of acute meningitis. An analysis of the predictive value of initial observations. JAMA 1989;262:2700–7. [8] Wu HM, Cordeiro SM, Harcourt BH, Carvalho M, Azevedo J, Oliveira TQ, et al. Accuracy of real-time PCR, gram stain and culture for Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae meningitis diagnosis. BMC Infect Dis 2013;13:26. [9] Schuetz P, Albrich W, Mueller B. Procalcitonin for diagnosis of infection and guide to antibiotic decisions: past, present and future. BMC Med 2011;9:107. [10] Gilbert DN. Use of plasma procalcitonin levels as an adjunct to clinical microbiology. J Clin Microbiol 2010;48:2325–9. [11] Simon L, Gauvin F, Amre DK, Saint-Louis P, Lacroix J. Serum procalcitonin and C-reactive protein levels as markers of bacterial infection: a systematic review and meta-analysis. Clin Infect Dis 2004;39:206–17. [12] Viallon A, Desseigne N, Marjollet O, Birynczyk A, Belin M, Guyomarch S, et al. Meningitis in adult patients with a negative direct cerebrospinal fluid examination: value of cytochemical markers for differential diagnosis. Crit Care 2011;15:R136. [13] Choi SH, Choi SH. Predictive performance of serum procalcitonin for the diagnosis of bacterial meningitis after neurosurgery. Infect Chemother 2013;45:308–14. [14] Li Y, Zhang G, Ma R, Du Y, Zhang L, Li F, et al. The diagnostic value of cerebrospinal fluids procalcitonin and lactate for the differential diagnosis of post-neurosurgical bacterial meningitis and aseptic meningitis. Clin Biochem 2015;48:50–4. [15] Jereb M, Muzlovic I, Hojker S, Strle F. Predictive value of serum and cerebrospinal fluid procalcitonin levels for the diagnosis of bacterial meningitis. Infection 2001; 29:209–12. [16] Schwarz S, Bertram M, Schwab S, Andrassy K, Hacke W. Serum procalcitonin levels in bacterial and abacterial meningitis. Crit Care Med 2000;28:1828–32. [17] Tunkel AR, Hartman BJ, Kaplan SL, Kaufman BA, Roos KL, Scheld WM, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis 2004;39: 1267–84. [18] DeLong ER, DeLong DM, Clarke-Pearson DL. Comparing the areas under two or more correlated receiver operating characteristic curves: a nonparametric approach. Biometrics 1988;44:837–45. [19] Ray P, Badarou-Acossi G, Viallon A, Boutoille D, Arthaud M, Trystram D, et al. Accuracy of the cerebrospinal fluid results to differentiate bacterial from non bacterial meningitis, in case of negative gram-stained smear. Am J Emerg Med 2007; 25:179–84. [20] Casado MI, Alonso FM, Pinedo BL, Julian-Jimenez A. Acute meningitis in the pediatric emergency department: diagnostic yield of procalcitonin and C-reactive protein. Pediatr Emerg Care 2014;30:849–50. [21] Makoo ZB, Soltani HR, Hasani A, Makoo RB, Mashrabi O. Diagnostic value of serum and cerebrospinal fluid procalcitonin in differentiation bacterial from aseptic meningitis. Am J Infect Dis 2010;6:93–7. [22] Linnet K, Bossuyt PM, Moons KG, Reitsma JB. Quantifying the accuracy of a diagnostic test or marker. Clin Chem 2012;58:1292–301. [23] Pencina MJ, D'Agostino Sr RB, D'Agostino Jr RB, Vasan RS. Evaluating the added predictive ability of a new marker: from area under the ROC curve to reclassification and beyond. Stat Med 2008;27:157–72 (discussion 207-12). [24] Whiting PF, Rutjes AW, Westwood ME, Mallett S, Deeks JJ, Reitsma JB, et al. Quadas2: a revised tool for the quality assessment of diagnostic accuracy studies. Ann Intern Med 2011;155:529–36.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
Contents lists available at ScienceDirect
Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem
Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis Hong-Yuan Shen a,1, Wei Gao b,1, Juan-Juan Cheng a, Shi-Di Zhao a, Yi Sun c, Zhi-Jun Han a,⁎, Jun Hua a,⁎ a b c
Department of Laboratory Medicine, Wuxi Second People's Hospital of Nanjing Medical University, Wuxi, PR China Department of Neurology, Wuxi New District Phoenix Hospital, Wuxi, PR China Department of Laboratory Diagnosis, Changhai Hospital, Second Military Medical University, Shanghai, PR China
a r t i c l e
i n f o
Article history: Received 6 May 2015 Received in revised form 23 June 2015 Accepted 24 June 2015 Available online xxxx Keywords: Meningitis PCT CSF Biomarker
a b s t r a c t Objective: To compare the clinical utility of serum and cerebrospinal fluid (CSF) procalcitonin (PCT) for the diagnosis of bacterial meningitis (BM) among patients with suspected meningitis. Methods: Patients with meningitis-like symptoms (n = 120), admitted to the Second People's Hospital of Wuxi or the Changhai Hospital of Shanghai between January 2011 and December 2013, were prospectively and consecutively enrolled in this study. BM was finally diagnosed by CSF culture, Gram staining, quantitative polymerase chain reaction (qPCR), and treatment response. The diagnostic accuracy of the serum and CSF PCT was assessed by receiver operator characteristic (ROC) curve analysis. The relationship between CSF and serum PCT levels as well as the CSF leukocyte count and protein level was analyzed by Spearman's correlation analysis. Results: PCT level in both the serum and CSF was significantly increased in the BM patients. The area under ROC curve of serum PCT for the diagnosis of BM was 0.96 (95% confidence interval (CI): 0.93–1.00), significantly higher than that of CSF PCT (0.90, 95% CI: 0.83–0.96). Using 0.88 ng/mL as the threshold, the diagnostic sensitivity, specificity, and accuracy of serum PCT for the diagnosis of BM were 0.87 (95% CI, 0.73–0.95), 1.00 (95% CI, 0.95–1.00), and 95%, respectively. The serum PCT level was positively correlated with the CSF PCT level, leukocyte count, and protein level. Conclusion: Both the serum and CSF PCT had a high diagnostic value for BM among suspected meningitis patients, and serum PCT demonstrated a superior diagnostic value compared to CSF PCT. © 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
1. Introduction Bacterial meningitis (BM) remains a common infectious disease with high mortality and constitutes a major medical concern to public health worldwide [1–3]. To a large extent, clinical manifestations among BM and viral meningitis, tuberculous meningitis, and fungal meningitis are similar; however, different treatment approaches are required for different pathogens. Thus, an early and accurate differential diagnosis is crucial [4,5]. Generally, the diagnosis of BM relies on microbiological tests and laboratory findings. Identifying of pathogens by cerebrospinal fluid (CSF) bacterial culture and Gram staining is highly specific; however, the sensitivity of bacterial culture and staining techniques is low as it has been reported that nearly half of BM patients had negative microbiological findings [6,7]. In addition, microbiological examination is time consuming, which makes an early diagnosis impossible. Analysis of leukocyte count and protein level in CSF is an alternative method for diagnosing BM, although the sensitivity and specificity ⁎ Corresponding authors at: Department of Laboratory Medicine, Wuxi Second People's Hospital of Nanjing Medical University, Wuxi, PR China. E-mail addresses: [email protected] (Z.-J. Han), [email protected] (J. Hua). 1 Both authors contributed equally to this work.
are not high enough to differentiate BM from viral meningitis, tuberculous meningitis, or fungal meningitis [7,8]. Therefore, it is necessary to identify more sensitive and specific biomarkers for the diagnosis of BM. In recent decades, procalcitonin (PCT), a polypeptide of 116 amino acids, has been reported to be an effective biomarker for bacterial infection [9,10]. A meta-analysis showed that the sensitivity and specificity of PCT for differentiating bacterial from viral infections were 0.92 and 0.86, respectively [11]. The PCT concentration in both serum and CSF of BM patients is increased, and both can serve as diagnostic markers for BM detection [12–15]. However, it is remains unknown whether serum or CSF PCT is better for the diagnosis of BM. Therefore, the aim of the present study was to compare the diagnostic accuracy between serum and CSF PCT determination in parallel. We focused our investigations on whether serum and CSF PCT had a high diagnostic value for BM among suspected meningitis patients. 2. Material and methods 2.1. Participants A total of 150 patients with meningitis-like manifestations, who were admitted to the Second People's Hospital of Wuxi or the Changhai
http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017 0009-9120/© 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
2
H.-Y. Shen et al. / Clinical Biochemistry xxx (2015) xxx–xxx
Hospital of Shanghai between January 2011 and December 2013, were prospectively and consecutively enrolled in this study. The inclusion criteria were as follows: 1) patients with two of the following symptoms or signs: fever, confusion, headache, or nuchal rigidity; 2) older than 18 years old; 3) no determination of a meningitis pathogen on admission; and 4) CSF leukocyte count greater than 5 × 106/L [16]. Patients who were infected with bacteria and received antibiotic therapy during the past two weeks were excluded. The present study was approved by the Ethics Committees of the Second People's Hospital of Wuxi and the Changhai Hospital of Shanghai. Written informed consent was obtained from all patients included in this study. 2.2. PCT test methods The serum and CSF samples were drawn within 8 h after admission. After completing routine bacterial and chemical analyses (e.g., CSF leukocyte count, protein level determination, and bacterial culture), the serum and CSF samples were stored immediately at − 80 °C. In June 2014, all the serum and CSF samples were subjected to PCT concentration determination by immunolumino-metric assay (LUMItest PCT, BRAHMS Diagnostica, Berlin, Germany). The laboratory technicians were blinded to the clinical information of the subjects. 2.3. Diagnosis of BM Leukocyte count and protein level were determined in the CSF samples from all admitted subjects. In addition, the blood and CSF samples were subjected to bacterial culture and Gram staining. Finally, the CSF samples were tested for viral infection, including CMV, ECHO, and HSV, by quantitative polymerase chain reaction (qPCR) to detect viral infection. Patients with positive CSF bacterial culture or Gram staining, but negative qPCR test, were diagnosed as BM, and antibiotic therapy was initiated immediately. The patients who tested positive for viral infection according to the qPCR test, but had negative CSF bacterial culture and Gram staining, were diagnosed as viral meningitis. For the cases with negative bacterial culture, Gram staining and qPCR, experimental therapy with antibiotics was introduced and the outcomes of the patients were documented [17]. The final diagnosis was made by two experienced physicians using the CSF laboratory findings and treatment response. 2.4. Statistical analysis For continuous variables, Mann–Whitney U test or Student's t-test was used to assess whether the differences had statistical significance. For categorical variables, χ2 test was used. Spearman's rank correlation coefficient was employed to analyze the relationship between two continuous variables. All continuous variables were reported as median (interquartile) or mean (SD) values. The diagnostic accuracy of PCT for BM was analyzed by receiver operator characteristic (ROC) curve analysis. The cut-off value for the PCT level was established by seeking the maximum accuracy (the proportion of true positive to true negative results). The areas under ROC curve (AUCs) were compared by the method developed by DeLong et al. [18]. P value of 0.05 or less was considered statistically significant. All tests were two-sided, and all statistical analyses were performed using SPSS version 17.0 (SPSS Inc., Chicago, IL, USA) and SigmaPlot 11.0 for Windows. 3. Results 3.1. Demographic and clinical characteristics of the subjects Of the 150 patients who were initially included in this study, 13 were returning patients and 17 had used antibiotics prior to admission. Finally, 120 meningitis patients were eligible for final analysis. All patients
were given an initial and a final diagnoses. Of these subjects, 30 who had a positive CSF or blood bacterial culture or Gram staining, but a negative PCR viral infection test, were initially diagnosed as BM. A total of 59 patients were categorized into the non-BM group because of positive PCR finding and negative CSF bacterial culture or Gram staining. For the remaining subjects, antibiotic therapy was initiated and the responses to the therapy were monitored. The final diagnosis was based on the patients' CSF leukocyte count, protein and glucose determination, as well as their responses to antibiotic therapy. Conclusively, 45 subjects were categorized into BM and 75 were categorized into the non-BM group. The clinical characteristics at baseline are shown in Table 1. Among the 75 non-BM patients, 18 were diagnosed as Coxsackie virus-induced meningitis, 17 were infected with the ECHO virus, 14 were infected with the herpes virus, 5 were infected with the EB virus, 3 were infected with the varicella zoster virus, 2 were infected with the paramyxovirus, and 16 were infected with an unknown virus. Among the BM group, 12 were infected with Streptococcus pneumoniae, 10 with Diplococcus intracellularis, 8 with Staphylococcus aureus, and 15 with unknown bacteria. 3.2. Increased serum and CSF PCT levels in the bacterial meningitis patients As shown in Fig. 1, the median serum concentration of PCT in the BM and non-BM patients was 4.22 ng/mL and 0.41 ng/mL, respectively. In addition, the CSF PCT concentration in the BM and non-BM patients was 1.88 ng/mL and 0.34 ng/mL, respectively. Both the serum and CSF PCT concentrations in the BM patients were significantly higher than those of the non-BM patients (P b 0.01 for both). 3.3. Relationship between the CSF and serum PCT levels in the BM and non-BM patients As shown in Fig. 2, the serum PCT level was positively correlated with the CSF PCT level among all meningitis patients, resulting in a correlation coefficient (R) of 0.64 (P b 0.01). We further analyzed the relationship between the serum and CSF PCT levels in the BM and non-BM patients, respectively. A significant positive correlation between the serum and CSF PCT levels (R = 0.69, P b 0.01) was observed in the BM patients but not in the non-BM patients. In addition, we also analyzed the relationships between the PCT level and the CSF leukocyte count as well as the CSF protein level. The serum PCT level was positively correlated with the CSF leukocyte count (R = 0.36, P = 0.02) and with the protein level (R = 0.39, P = 0.01) in the BM patients but not in the non-BM patients. 3.4. Diagnostic accuracy of the serum and CSF PCT levels for BM patients Fig. 3 shows the ROC curve of the serum and CSF PCT for the diagnosis of BM. The AUC for serum and CSF PCT was 0.96 (95% CI: 0.93–1.00) Table 1 Demographic and clinical characteristics of the subjects.
Number of patients Age (years) Gender (male/female) Clinical signs or symptoms Median period between symptom onset and admission (h) Fever (yes/no) Headache (yes/no) Nuchal rigidity (yes/no) Confusion (yes/no) CSF laboratory findings Leukocyte count (106/L) Protein (g/L)
BM
Non-BM
P
45 50 ± 18 30/15
75 47 ± 19 55/20
– 0.34 0.53
43 (25, 52)
43 (30, 54)
0.26
45/0 45/0 44/1 2/43
60/15 75/0 70/5 1/74
b0.01 1.00 0.41 0.55
3800 (620, 7500) 0.68 (0.40, 0.94)
280 (58, 500) b0.01 0.39 (0.25, 0.56) b0.01
Note: Values are the median and quartile, where appropriate.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
H.-Y. Shen et al. / Clinical Biochemistry xxx (2015) xxx–xxx
3
Fig. 1. Comparison of the serum and CSF PCT levels between the BM and non-BM patients. Note: Horizontal bars in the plots represent the mean values.
and 0.90 (95% CI: 0.83–0.96), respectively. The AUC for serum PCT was significantly higher than that for CSF PCT (P = 0.03), indicating that the serum PCT exhibits a significantly higher diagnostic accuracy than that of the CSF PCT. Table 2 shows the diagnostic sensitivity, specificity, and accuracy at a prespecified threshold (0.5 ng/mL) as well as the calculated threshold with maximum diagnostic accuracy. At the threshold of 0.88 ng/mL, the serum PCT showed the highest diagnostic accuracy (95.0%), implying that only 6 of the 120 meningitis patients were misdiagnosed. The highest diagnostic accuracy for CSF PCT was 83.3%, when a threshold of 0.74 ng/mL was selected. 4. Discussion The purpose of this study was to determine relative efficiency of serum and CSF PCT for diagnosis of BM. We found that PCT level in both serum and CSF of BM patients was significantly higher than that of non-BM patients. Our findings were as expected [14], since PCT is a well-recognized marker for bacterial infection [12,13,19,20]. Thus, the results from this study corroborate that PCT in serum and CSF is a potential diagnostic marker for BM. Previously, two studies have evaluated the diagnostic accuracy of both serum and CSF PCT in the same cohorts [15,21]; however, the diagnostic accuracy of serum and CSF PCT was not compared. To the best of our knowledge, this study was the first one to compare the diagnostic accuracy of two PCTs in a head-to-head manner, thus eliminating potential variations at different settings. Unlike sensitivity and specificity, which can be greatly affected by the threshold chosen, the AUC is a global parameter that estimates the diagnostic accuracy of an index test [22]. We assessed the diagnostic
Fig. 2. Correlations between the serum and CSF PCT levels in all meningitis patients (BM and non-BM). Note: Data were analyzed using the Spearman's correlation.
accuracy of both serum and CSF PCT by ROC curve analysis. A significantly higher AUC was established using serum PCT. Therefore, we concluded that the overall diagnostic accuracy of serum PCT was superior to CSF PCT in this cohort. Of note, the diagnostic accuracy of serum PCT was 95% at cut-off of 0.88 ng/mL, implying that 95% of patients with suspected meningitis can be correctly differentiated. At this cut-off value, the diagnostic specificity was 100%, implying that a patient without BM is very unlikely to have serum PCT level higher than 0.88 ng/mL. Our data suggest that the serum PCT could be a reliable marker to distinguish BM from viral meningitis. A positive correlation between the serum and CSF PCT levels was observed in our study, and this finding has not been reported previously [15,21]. Such correlation may suggest that CSF PCT may originate from serum, since the serum PCT level was higher than that of the CSF PCT level. During the pathogenic process of meningitis, the blood–brain barrier is damaged by the inflammatory response, and PCT in the blood is able to enter into the CSF. This process could explain why CSF PCT was of high diagnostic accuracy for BM. We also found that the serum PCT level was significantly and positively correlated with the CSF leukocyte count and protein level. It is well established that the CSF leukocyte count and protein level are effective indices for the differential diagnosis of meningitis. Therefore, the detection of serum PCT is a valuable addition to CSF leukocyte count and protein level determination; in addition, it saves time and makes an early and accurate diagnosis of BM possible. As the present study was limited by its small sample size, we were unable to use rigorous statistical models such as net reclassification or integrated discrimination improvement [23] to determine whether serum PCT can improve the diagnostic accuracy of CSF leukocyte count and protein level, or the converse is true. One strength of the present study should be noted. To ensure that the detected BM prevalence reflected the clinical reality [24], all the subjects in the present study were consecutively enrolled. That is why we
Fig. 3. ROC curves of the serum and CSF PCT for the diagnosis of BM.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
4
H.-Y. Shen et al. / Clinical Biochemistry xxx (2015) xxx–xxx
Table 2 Comparison of diagnostic efficiency between serum and CSF PCT at different thresholds.
Serum PCT CSF PCT
Cut-off value
Sensitivity (95% CI)
Specificity (95% CI)
Accuracy (%)
0.50 ng/mL 0.88 ng/mL 0.50 ng/mL 0.74 ng/mL
0.98 (0.88–1.00) 0.87 (0.73–0.95) 0.82 (0.68–0.92) 0.69 (0.53–0.82)
0.65 (0.53–0.76) 1.00 (0.95–1.00) 0.81 (0.71–0.89) 1.00 (0.95–1.00)
77.5 95.0 81.7 88.3
did not exclude the subjects who did not have identifiable microbiological findings from the final analysis. As reported, only 70%–85% of BM patients are positive for bacterial culture, and the sensitivity of qPCR for viral meningitis is about 90% [17], indicating that the final diagnosis of some BM and non-BM patients must be based on the clinical symptoms or signs, CSF laboratory findings and antibiotic treatment responses. In summary, we found that both serum and CSF PCT had high diagnostic value for BM among suspected meningitis patients. In addition, serum PCT exhibited a superior diagnostic value compared to CSF PCT. Therefore, we recommend that serum PCT should be the first choice for diagnosing BM. Disclosures The authors declare no conflict of interest. Acknowledgments This work was supported by a grant from the National Natural Science Foundation of China (no. 81301503). References [1] Castelblanco RL, Lee M, Hasbun R. Epidemiology of bacterial meningitis in the USA from 1997 to 2010: a population-based observational study. Lancet Infect Dis 2014;14:813–9. [2] Snaebjarnardottir K, Erlendsdottir H, Reynisson IK, Kristinsson K, Halldorsdottir S, Hardardottir H, et al. Bacterial meningitis in children in Iceland, 1975–2010: a nationwide epidemiological study. Scand J Infect Dis 2013;45:819–24. [3] Stockmann C, Ampofo K, Byington CL, Filloux F, Hersh AL, Blaschke AJ, et al. Pneumococcal meningitis in children: epidemiology, serotypes, and outcomes from 1997– 2010 in Utah. Pediatrics 2013;132:421–8. [4] Brouwer MC, Thwaites GE, Tunkel AR, Van De Beek D. Dilemmas in the diagnosis of acute community-acquired bacterial meningitis. Lancet 2012;380:1684–91.
[5] Brouwer MC, Tunkel AR, van de Beek D. Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis. Clin Microbiol Rev 2010;23:467–92. [6] Yadhav Ml K. Study of bacterial meningitis in children below 5 years with comparative evaluation of gram staining, culture and bacterial antigen detection. J Clin Diagn Res 2014;8:DC04–6. [7] Spanos A, Harrell Jr FE, Durack DT. Differential diagnosis of acute meningitis. An analysis of the predictive value of initial observations. JAMA 1989;262:2700–7. [8] Wu HM, Cordeiro SM, Harcourt BH, Carvalho M, Azevedo J, Oliveira TQ, et al. Accuracy of real-time PCR, gram stain and culture for Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae meningitis diagnosis. BMC Infect Dis 2013;13:26. [9] Schuetz P, Albrich W, Mueller B. Procalcitonin for diagnosis of infection and guide to antibiotic decisions: past, present and future. BMC Med 2011;9:107. [10] Gilbert DN. Use of plasma procalcitonin levels as an adjunct to clinical microbiology. J Clin Microbiol 2010;48:2325–9. [11] Simon L, Gauvin F, Amre DK, Saint-Louis P, Lacroix J. Serum procalcitonin and C-reactive protein levels as markers of bacterial infection: a systematic review and meta-analysis. Clin Infect Dis 2004;39:206–17. [12] Viallon A, Desseigne N, Marjollet O, Birynczyk A, Belin M, Guyomarch S, et al. Meningitis in adult patients with a negative direct cerebrospinal fluid examination: value of cytochemical markers for differential diagnosis. Crit Care 2011;15:R136. [13] Choi SH, Choi SH. Predictive performance of serum procalcitonin for the diagnosis of bacterial meningitis after neurosurgery. Infect Chemother 2013;45:308–14. [14] Li Y, Zhang G, Ma R, Du Y, Zhang L, Li F, et al. The diagnostic value of cerebrospinal fluids procalcitonin and lactate for the differential diagnosis of post-neurosurgical bacterial meningitis and aseptic meningitis. Clin Biochem 2015;48:50–4. [15] Jereb M, Muzlovic I, Hojker S, Strle F. Predictive value of serum and cerebrospinal fluid procalcitonin levels for the diagnosis of bacterial meningitis. Infection 2001; 29:209–12. [16] Schwarz S, Bertram M, Schwab S, Andrassy K, Hacke W. Serum procalcitonin levels in bacterial and abacterial meningitis. Crit Care Med 2000;28:1828–32. [17] Tunkel AR, Hartman BJ, Kaplan SL, Kaufman BA, Roos KL, Scheld WM, et al. Practice guidelines for the management of bacterial meningitis. Clin Infect Dis 2004;39: 1267–84. [18] DeLong ER, DeLong DM, Clarke-Pearson DL. Comparing the areas under two or more correlated receiver operating characteristic curves: a nonparametric approach. Biometrics 1988;44:837–45. [19] Ray P, Badarou-Acossi G, Viallon A, Boutoille D, Arthaud M, Trystram D, et al. Accuracy of the cerebrospinal fluid results to differentiate bacterial from non bacterial meningitis, in case of negative gram-stained smear. Am J Emerg Med 2007; 25:179–84. [20] Casado MI, Alonso FM, Pinedo BL, Julian-Jimenez A. Acute meningitis in the pediatric emergency department: diagnostic yield of procalcitonin and C-reactive protein. Pediatr Emerg Care 2014;30:849–50. [21] Makoo ZB, Soltani HR, Hasani A, Makoo RB, Mashrabi O. Diagnostic value of serum and cerebrospinal fluid procalcitonin in differentiation bacterial from aseptic meningitis. Am J Infect Dis 2010;6:93–7. [22] Linnet K, Bossuyt PM, Moons KG, Reitsma JB. Quantifying the accuracy of a diagnostic test or marker. Clin Chem 2012;58:1292–301. [23] Pencina MJ, D'Agostino Sr RB, D'Agostino Jr RB, Vasan RS. Evaluating the added predictive ability of a new marker: from area under the ROC curve to reclassification and beyond. Stat Med 2008;27:157–72 (discussion 207-12). [24] Whiting PF, Rutjes AW, Westwood ME, Mallett S, Deeks JJ, Reitsma JB, et al. Quadas2: a revised tool for the quality assessment of diagnostic accuracy studies. Ann Intern Med 2011;155:529–36.
Please cite this article as: Shen H-Y, et al, Direct comparison of the diagnostic accuracy between blood and cerebrospinal fluid procalcitonin levels in patients with meningitis, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.017
