Radiologic Resident Education
Resident Experience Increases Diagnostic Rate of Thyroid Fine-Needle Aspiration Biopsies Michael D. Beland, MD, Thomas J. T. Anderson, MD, Michael K. Atalay, MD, David J. Grand, MD, John J. Cronan, MD Rationale and Objectives: The aim of this study was to determine whether the diagnostic yield of thyroid fine-needle aspirations (FNAs) changes over the course of residency training. Materials and Methods: We identified 5418 ultrasound-guided thyroid nodule FNAs performed in our radiology department from 2004 through 2012. For each FNA, we recorded if the FNA was performed by a resident and if so the name of the resident and supervising attending radiologist. For each resident, we determined the level of training based on their graduation year from our residency program and the date of the FNA as well as prior surgical training and if they completed subsequent interventional radiology fellowship. Pathology reports were reviewed, and FNAs were classified as diagnostic or nondiagnostic (ND). Generalized mixed models were used to assess ND rate with postgraduate years, including residents with and without prior surgical training or if they subsequently completed an interventional radiology fellowship. Results: Of the 5418 thyroid FNAs, 3164 (58.4%) were performed by a radiology resident under the direct supervision of an attending physician. There was a significant decrease in ND rate as postgraduate years increased (P < .05). A significant decrease in ND rate was found as postgraduate years increased for residents without prior surgical training (P = .0007) or subsequent training in interventional radiology (P = .0014); however, no significant decrease was found for residents with surgical training (P = .37) or completing an interventional radiology fellowship (P = .08). In addition, no significant difference was found for ND rate between postgraduate year 4 (PGY4) and PGY5 (P > .05). Conclusions: ND thyroid FNA rates progressively decrease with training level, suggesting that early and continued participation in procedures throughout residency improves outcomes. This is particularly true for residents without prior surgical training or subsequent interventional radiology fellowship. Key Words: Thyoid; FNA; fine needle aspriration; biopsy; resident training. ªAUR, 2014
T
hyroid nodules are common and typically benign. Current clinical guidelines recommend fine-needle aspiration (FNA) of nodules > 1–1.5 cm, and of smaller nodules with concerning sonographic features (1–3). The reported diagnostic yield of thyroid FNA varies from 80% to 99%, with an average of 85% (4–8). Although it is well documented that diagnostic rates can be improved by routine onsite cytopathology evaluation for adequacy, it is expensive and inefficient, particularly at high volume centers (9–15). The effect of biopsy technique on nondiagnostic (ND) rates has also been studied. For example, two studies have
Acad Radiol 2014; 21:1490–1494 From the Department of Diagnostic Imaging, Rhode Island Hospital, 593 Eddy St, Providence, RI 02903 (M.D.B., M.K.A., D.J.G., J.J.C.) and Department of Medicine, Roger Williams Medical Center, Providence, Rhode Island (T.J.A.). Received September 24, 2013; accepted June 19, 2014. Address correspondence to: M.D.B. e-mail: [email protected] ªAUR, 2014 http://dx.doi.org/10.1016/j.acra.2014.06.006
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demonstrated equal efficacy of aspiration versus suctionassisted FNA techniques (16,17). Visualization of the needle within the nodule along its long axis has been shown to improve diagnostic rates for deep nodules when compared with visualization along the needle’s short axis (18). Needle size seems to be relatively unimportant as studies comparing needles from 21 to 27 ga have not shown a diagnostic advantage of the larger bore needles (18–20). One small study showed no difference in ND rates between an experienced attending radiologist and a new attending radiologist (21). Another study examining attending pathologists’ interpretations of thyroid FNA based on number of years of experience found that less experienced pathologists were more likely to interpret samples as ND or atypical, whereas more experienced pathologists were more likely to interpret samples as benign (22). To our knowledge, the effect of resident training level on ND thyroid FNA rates is unknown. The aim of this study was to determine whether the diagnostic yield of thyroid FNA changes over the course of residency training.
Academic Radiology, Vol 21, No 11, November 2014
RESIDENT EXPERIENCE DECREASES ND RATE OF FNA
TABLE 1. ND FNA Rates by Level of Training, Comparing Residents with and without Prior Surgical Training, and Whether They Completed a Subsequent Interventional Radiology Fellowship ND Rate (%) Level of Training PGY2 PGY3 PGY4 PGY5
Surgery (95% CI)
No Surgery (95% CI)
Interventional Radiology (95% CI)
No Interventional Radiology (95% CI)
14.7 (10.5–20.2) 15.3 (10.3–22.0) 9.9 (5.2–18.1) 13.3 (9.0–19.1)
18.2 (15.6–21.3) 16.8 (14.4–19.6) 12.7 (10.2–15.6) 11.7 (9.1–14.8)
14.6 (11.1–19.0) 17.9 (13.2–23.9) 14.4 (9.4–21.3) 9.5 (6.0–14.7)
18.8 (16.0–22.0) 16.3 (13.8–19.2) 11.9 (9.5–14.8) 12.5 (9.8–15.8)
CI, confidence interval; FNA, fine-needle aspiration; ND, nondiagnostic; PGY, postgraduate year.
MATERIALS AND METHODS Through a search of our pathology departmental database (CoPath; Cerner Corporation, North Kansas City, MO), we identified 5418 nodules that underwent ultrasound-guided FNA in our radiology department between 2004 and 2012. Patients were 82.7% women, with an average age at biopsy of 54.8 15.4 years. All patients underwent a sonographic examination of the thyroid by an ultrasound technologist using high-frequency linear transducers (9–14 MHz; LOGIQ 9 and LOGIQ E9 ultrasound units; GE Healthcare, Wauwatosa, WI) before the requested FNA. Images were reviewed by an attending radiologist specializing in sonography. Ultrasound-guided FNAs were performed by a radiology resident under direct supervision of an attending radiologist. Standard FNA technique at our institution includes 1% buffered lidocaine for local anesthesia followed by five passes with 25- or 27-ga needles using capillary technique. The needle is monitored in real time for all passes using long-axis needle visualization. Samples were collected into 30-mL Cytolyt (Cytyc Corporation, Londonderry, NH) for processing in the cytology department after completion of the FNA. Standard thin sections were reviewed by an attending cytologist. Our cytology department uses standard sample adequacy criteria, which classify a sample ND if it has fewer than six groupings of at least 10 thyroid follicular cells each (23). The medical record was then reviewed and the following information was recorded: 1) the result of the FNA, classified as diagnostic or ND, 2) the resident and supervising attending who performed the FNA, and 3) the date the FNA was performed. Through review of our residency program’s records, the graduation year of each resident was used to determine the postgraduate year of training at the time of a given FNA. We also recorded if a resident had surgical residency training of at least 1 year before radiology residency and if a resident subsequently completed an interventional radiology fellowship. Generalized mixed modeling assuming a binominal distribution with classic sandwich estimation to adjust for any model misspecification was used to model diagnostic rate as a function of postgraduate year along with background in surgery or subsequent interventional radiology (SAS Software 9.3/PROC GLIMMIX; SAS Institute, Cary, NC). Multiple
Figure 1. Nondiagnostic thyroid fine-needle aspiration rate for residents with and without surgical training.
comparisons were examined using the Holm method with orthogonal linear contrasts. Statistical significance was predefined as P < .05. This study was Health Insurance Portability and Accountability Act compliant and received institutional review board approval.
RESULTS Of the 5418 thyroid FNAs performed in our radiology department, 3164 were performed by a resident under the direct supervision of an attending physician. Of the 74 residents, 8 (10.8%) were identified as having previous surgical training and 12 (16.2%) subsequently completed an interventional radiology training fellowship. It should be noted that five residents had both prior surgical and subsequent intervention radiology training. Results are summarized in Table 1. Mixed model examining residents with and without surgical training revealed a significant decrease in ND rate as postgraduate year increased (P = .0012). Moreover, post hoc follow-up analyses revealed a significant decrease in ND rate for residents without surgical training (P = .0007); conversely, no significant decrease was detected for residents with surgical training (P = .37; Fig 1). 1491
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Figure 2. Nondiagnostic thyroid fine-needle aspiration rate for residents who did and did not subsequently complete interventional radiology fellowship.
No significant difference was detected between the prior surgical and nonsurgical residents (P = .33). In addition, no significant difference was detected between postgraduate year 4 (PGY4) and PGY5 (P = .23). Likewise, a mixed model examining residents who did or did not subsequently complete an interventional radiology fellowship revealed an overall significant decrease in ND rate as postgraduate year increased (P = .0009). Post hoc follow-up analyses revealed a significant decrease in ND rate for residents not completing an interventional radiology fellowship (P = .0014), but for residents going on to interventional radiology fellowship, the decrease only approached significance (P = .08; Fig 2). Again, no significant difference was detected between residents with and without subsequent interventional radiology training (P = .94). In addition, the difference between PGY4 and PGY5 only approached significance (P = .08).
DISCUSSION To our knowledge, this is the only study to date examining how radiology resident seniority impacts diagnostic rates of thyroid FNA. We found that ND rates decreased as postgraduate year increased. This suggests that operator training and experience can have a significant effect on tissue sample adequacy. Our results support that early and continued performance of even simpler procedures such as thyroid FNA throughout residency training offers improved outcomes. This appears to be particularly true for residents who do not have prior surgical experience or interest in interventional radiology as evidenced by significant improvements in ND rates for residents without prior surgical training or not going on to complete an interventional radiology fellowship. The overall ND rate for thyroid FNA performed by radiology residents in this study was 15.3%, which is concordant with current literature (4–8). Prior studies have shown that multiple factors can improve the ND rate of thyroid
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FNA. For example, routine onsite cytopathology evaluation for adequacy has been shown to improve diagnostic rates (9–13). Recently, studies have assessed the ability of a cytopathology technician to determine sample adequacy and found no clinically significant difference between experienced cytopathology technician assessment and attending pathologist assessment (24,25). Furthermore, in one study, biopsies performed with cytopathology technicians were $464.10 less expensive than biopsies performed with attending pathologists (24). Prior studies have shown no significant difference in the yield of aspiration versus capillary technique, with the latter being standardly used at our institution (16,17). As recommended by the National Cancer Institute, we use 25- or 27-ga needles at our institution depending on attending preference with prior studies showing no significant difference in diagnostic yield between the two gauges (18,19,23). Finally, we perform thyroid FNAs using the long-axis technique which has been shown to improve diagnostic rates for deep nodules when compared to visualization along its short axis (18). Prior studies have examined the effect of radiology resident training year on preliminary interpretations of imaging studies. For example, Bruni et al. recently evaluated 5695 preliminary resident interpretations of neuroradiology studies and showed a nearly linear downward trend in the discrepancy rate with increasing resident training level (26). Another study of preliminary radiology resident interpretations in the emergency department found that the overall rate of reported discrepancies was low for all levels of training (0.23%–0.42 %) but did demonstrate a small, but statistically significant, decrease in the discrepancy rate for the senior residents (27). Based on their findings, the authors recommended that radiology resident training programs ensure that common discrepancies are specifically addressed as part of a dedicated emergency radiology course. However, another study performed after implementation of a dedicated emergency radiology course showed length of dedicated emergency radiology training before taking call made no significant difference. Of the variables assessed, only the resident training year showed a significant difference in scoring parameters (28). Effect of radiology training on performance of procedures is less well studied. A study in 2010 evaluated the complication rates and outcomes of 536 implanted subcutaneous chest ports placed by interventional radiology. They showed no significant difference in overall complication rates of ports placed between residents, physician extenders, fellows, and attendings (29). A more recent study found that when central venous catheters are placed by radiology residents, fluoroscopy time is double that for identical procedures performed by staff radiologists (30). They did not, however, demonstrate a linear correlation between fluoroscopy time and resident seniority, suggesting that increasing years of training for residents does not reduce the fluoroscopy time. The authors suggest that other factors such as fellowship training, increased awareness of radiation dose reduction tactics, or overall higher career procedure volumes may all contribute.
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Given our results demonstrating that a residents’ diagnostic yield improves over time, this may suggest a benefit to increased training in thyroid FNA technique perhaps using simulation phantoms of other methods of additional training early in residency. Training by simulation models has been described in radiology. Villard et al. developed a virtual simulator to teach liver biopsy through creation of a robust and real-time simulation environment combining a physical platform and an immersive computerized virtual environment (31). Meng et al. have described a picture archiving and communication system–integrated ultrasound-guided breast biopsy simulation exercise during radiology residency and found it increased residents’ procedural confidence and understanding of the American College of Radiology practice guideline for the performance of ultrasound-guided percutaneous breast interventional procedures (32). More hands-on interactive teaching devices have also been created, such as a device to teach residents pediatric intussusception reduction and a simulator to teach the Seldinger technique and angiography training (33,34). A current trend in medical resident training has been the development of simulation centers to provide an immersive training environment. One academic practice has utilized a simulation center to improve resident proficiency in multiple ultrasound-guided procedures (35). A potential limitation of our study is selection bias. However, generally nodules conceived as more difficult or more likely to be ND would be performed by a more experienced resident. The ultrasound department at our institution is staffed by both a junior and a senior resident. The larger more superficial solid nodules are preferentially biopsied by the more junior resident, whereas the smaller, cystic, or prior ND nodules are preferentially biopsied by the more senior resident. Therefore, if this bias affected our results, it could conceivably favor fewer ND results by the junior residents and decrease the differences between years of training. We do not use routine onsite cytology when performing thyroid FNA, which might have improved the diagnostic yield at all levels. An additional limitation is the lack of knowledge as to the level of attending involvement. For example, an attending may have felt that the sample acquired by the resident was inadequate or there were other difficulties in obtaining the FNA, and the attending may have therefore performed some of the passes themselves. However, again, this limitation would most likely lead to a smaller difference in the diagnostic yield between levels of training. Finally, Because of the retrospective nature of the study, we are unable to evaluate confounding factors such as patient body habitus, body mass index, or neck length as contributors to an ND biopsy as these were not recorded at time of initial FNA. In conclusion, senior radiology residents achieve significantly lower ND thyroid biopsy rates than junior residents, who may benefit from more intensive training in FNA technique early in their training. This benefit is most apparent in residents without a surgical background or strong interest in interventional radiology.
RESIDENT EXPERIENCE DECREASES ND RATE OF FNA
REFERENCES 1. Frates MC, Benson CB, Charboneau JW, et al. Management of thyroid nodules detected at US: society of radiologists in ultrasound consensus conference statement. Radiology 2005; 237(3):794–800. 2. Cibas ES, Alexander EK, Benson CB, et al. Indications for thyroid FNA and pre-FNA requirements: a synopsis of the national cancer institute thyroid fine-needle aspiration state of the science conference. Diagn Cytopathol 2008; 36(6):390–399. 3. American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer, Cooper DS, Doherty GM, Haugen BR, et al. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 2009; 19(11):1167–1214. 4. Ceresini G, Corcione L, Morganti S, et al. Ultrasound-guided fine-needle capillary biopsy of thyroid nodules, coupled with on-site cytologic review, improves results. Thyroid 2004; 14(5):385–389. 5. Yassa L, Cibas ES, Benson CB, et al. Long-term assessment of a multidisciplinary approach to thyroid nodule diagnostic evaluation. Cancer 2007; 111(6):508–516. 6. Yang J, Schnadig V, Logrono R, et al. Fine-needle aspiration of thyroid nodules: a study of 4703 patients with histologic and clinical correlations. Cancer 2007; 111(5):306–315. 7. Nayar R, Ivanovic M. The indeterminate thyroid fine-needle aspiration: experience from an academic center using terminology similar to that proposed in the 2007 national cancer institute thyroid fine needle aspiration state of the science conference. Cancer 2009; 117(3):195–202. 8. Gharib H, Goellner JR. Fine-needle aspiration biopsy of the thyroid: an appraisal. Ann Intern Med 1993; 118(4):282–289. 9. Zhu W, Michael CW. How important is on-site adequacy assessment for thyroid FNA? An evaluation of 883 cases. Diagn Cytopathol 2007; 35(3): 183–186. 10. Gomez-Macias GS, Garza-Guajardo R, Segura-Luna J, et al. Inadequate fine needle aspiration biopsy samples: pathologists versus other specialists. Cytojournal 2009; 6:9. 11. Poller DN, Kandaswamy P. A simplified economic approach to thyroid FNA cytology and surgical intervention in thyroid nodules. J Clin Pathol 2013; 66(7):583–588. 12. Redman R, Zalaznick H, Mazzaferri EL, et al. The impact of assessing specimen adequacy and number of needle passes for fine-needle aspiration biopsy of thyroid nodules. Thyroid 2006; 16(1):55–60. 13. Abraham TM, de las Morenas A, Lee SL, et al. In thyroid fine-needle aspiration, use of bedside-prepared slides significantly increased diagnostic adequacy and specimen cellularity relative to solution-based samples. Thyroid 2011; 21(3):237–242. 14. O’Malley ME, Weir MM, Hahn PF, et al. US-guided fine-needle aspiration biopsy of thyroid nodules: adequacy of cytologic material and procedure time with and without immediate cytologic analysis. Radiology 2002; 222(2):383–387. 15. Eedes CR, Wang HH. Cost-effectiveness of immediate specimen adequacy assessment of thyroid fine-needle aspirations. Am J Clin Pathol 2004; 121(1):64–69. 16. Tublin ME, Martin JA, Rollin LJ, et al. Ultrasound-guided fine-needle aspiration versus fine-needle capillary sampling biopsy of thyroid nodules: does technique matter? J Ultrasound Med 2007; 26(12):1697–1701. 17. de Carvalho GA, Paz-Filho G, Cavalcanti TC, et al. Adequacy and diagnostic accuracy of aspiration vs. capillary fine needle thyroid biopsies. Endocr Pathol 2009; 20(4):204–208. 18. Kandil E, Khalek MA, Alabbas H, et al. Comparison of ultrasound-guided biopsy technique for thyroid nodules with respect to adequacy of cytological material. J Otorhinolaryngol Relat Spec 2011; 73(4):177–181. 19. Degirmenci B, Haktanir A, Albayrak R, et al. Sonographically guided fine-needle biopsy of thyroid nodules: the effects of nodule characteristics, sampling technique, and needle size on the adequacy of cytological material. Clin Radiol 2007; 62(8):798–803. 20. Gumus M, Cay N, Algin O, et al. Comparison of 21 and 27 gauge needles for determining sample adequacy in the aspiration biopsy of thyroid nodules. Diagn Interv Radiol 2012; 18(1):102–105. 21. Lee YJ, Kim DW, Jung SJ. Comparison of sample adequacy, pain-scale ratings, and complications associated with ultrasound-guided fine-needle aspiration of thyroid nodules between two radiologists with different levels of experience. Endocrine 2013 Feb 21 [Epub ahead of print].
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22. Houlton JJ, Sun GH, Fernandez N, et al. Thyroid fine-needle aspiration: does case volume affect diagnostic yield and interpretation? Arch Otolaryngol Head Neck Surg 2011; 137(11):1136–1139. 23. Baloch ZW, Cibas ES, Clark DP, et al. The national cancer institute thyroid fine needle aspiration state of the science conference: a summation. Cytojournal 2008; 5:6. 6413-5-6. 24. Wotruba AL, Stewart J, 3rd, Scheberl T, et al. Added value, decreased cost: the evolving role of the cytotechnologist for preliminary screening and triage of thyroid aspirates. Diagn Cytopathol 2011; 39(12):896–899. 25. Olson MT, Tatsas AD, Ali SZ. Cytotechnologist-attended on-site adequacy evaluation of thyroid fine-needle aspiration: comparison with cytopathologists and correlation with the final interpretation. Am J Clin Pathol 2012; 138(1):90–95. 26. Bruni SG, Bartlett E, Yu E. Factors involved in discrepant preliminary radiology resident interpretations of neuroradiological imaging studies: a retrospective analysis. AJR 2012; 198(6):1367–1374. 27. Tomich J, Retrouvey M, Shaves S. Emergency imaging discrepancy rates at a level 1 trauma center: identifying the most common on-call resident ‘‘misses.’’ Emerg Radiol 2013; Jul 26 [Epub ahead of print]. 28. Khan R, Krupinski E, Graham JA, et al. Assessing first year radiology resident competence pre-call: development and implementation of a computer-based exam before and after the 12 month training requirement. Acad Radiol 2012; 19(6):752–758.
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29. Silas AM, Perrich KD, Hoffer EK, et al. Complication rates and outcomes of 536 implanted subcutaneous chest ports: do rates differ based on the primary operator’s level of training? Acad Radiol 2010; 17(4):464–467. 30. Xu BJ, Duszak R, Jr, McGinnis RS, et al. Increased fluoroscopy time for central venous catheter placement by radiology residents versus staff radiologists. J Am Coll Radiol 2013; 10(7):518–522. 31. Villard PF, Vidal FP, Ap Cenydd L, et al. Interventional radiology virtual simulator for liver biopsy. Int J Comput Assist Radiol Surg 2013; Jul 24 [Epub ahead of print]. 32. Meng K, Lipson JA. Utilizing a PACS-integrated ultrasound-guided breast biopsy simulation exercise to reinforce the ACR practice guideline for ultrasound-guided percutaneous breast interventional procedures during radiology residency. Acad Radiol 2011; 18(10):1324–1328. 33. Stein-Wexler R, Sanchez T, Roper GE, et al. An interactive teaching device simulating intussusception reduction. Pediatr Radiol 2010; 40(11): 1810–1815. 34. Luboz V, Zhang Y, Johnson S, et al. ImaGiNe Seldinger: first simulator for Seldinger technique and angiography training. Comput Methods Programs Biomed 2013; 111(2):419–434. 35. Mendiratta-Lala M, Williams T, de Quadros N, et al. The use of a simulation center to improve resident proficiency in performing ultrasound-guided procedures. Acad Radiol 2010; 17(4):535–540.
Resident Experience Increases Diagnostic Rate of Thyroid Fine-Needle Aspiration Biopsies Michael D. Beland, MD, Thomas J. T. Anderson, MD, Michael K. Atalay, MD, David J. Grand, MD, John J. Cronan, MD Rationale and Objectives: The aim of this study was to determine whether the diagnostic yield of thyroid fine-needle aspirations (FNAs) changes over the course of residency training. Materials and Methods: We identified 5418 ultrasound-guided thyroid nodule FNAs performed in our radiology department from 2004 through 2012. For each FNA, we recorded if the FNA was performed by a resident and if so the name of the resident and supervising attending radiologist. For each resident, we determined the level of training based on their graduation year from our residency program and the date of the FNA as well as prior surgical training and if they completed subsequent interventional radiology fellowship. Pathology reports were reviewed, and FNAs were classified as diagnostic or nondiagnostic (ND). Generalized mixed models were used to assess ND rate with postgraduate years, including residents with and without prior surgical training or if they subsequently completed an interventional radiology fellowship. Results: Of the 5418 thyroid FNAs, 3164 (58.4%) were performed by a radiology resident under the direct supervision of an attending physician. There was a significant decrease in ND rate as postgraduate years increased (P < .05). A significant decrease in ND rate was found as postgraduate years increased for residents without prior surgical training (P = .0007) or subsequent training in interventional radiology (P = .0014); however, no significant decrease was found for residents with surgical training (P = .37) or completing an interventional radiology fellowship (P = .08). In addition, no significant difference was found for ND rate between postgraduate year 4 (PGY4) and PGY5 (P > .05). Conclusions: ND thyroid FNA rates progressively decrease with training level, suggesting that early and continued participation in procedures throughout residency improves outcomes. This is particularly true for residents without prior surgical training or subsequent interventional radiology fellowship. Key Words: Thyoid; FNA; fine needle aspriration; biopsy; resident training. ªAUR, 2014
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hyroid nodules are common and typically benign. Current clinical guidelines recommend fine-needle aspiration (FNA) of nodules > 1–1.5 cm, and of smaller nodules with concerning sonographic features (1–3). The reported diagnostic yield of thyroid FNA varies from 80% to 99%, with an average of 85% (4–8). Although it is well documented that diagnostic rates can be improved by routine onsite cytopathology evaluation for adequacy, it is expensive and inefficient, particularly at high volume centers (9–15). The effect of biopsy technique on nondiagnostic (ND) rates has also been studied. For example, two studies have
Acad Radiol 2014; 21:1490–1494 From the Department of Diagnostic Imaging, Rhode Island Hospital, 593 Eddy St, Providence, RI 02903 (M.D.B., M.K.A., D.J.G., J.J.C.) and Department of Medicine, Roger Williams Medical Center, Providence, Rhode Island (T.J.A.). Received September 24, 2013; accepted June 19, 2014. Address correspondence to: M.D.B. e-mail: [email protected] ªAUR, 2014 http://dx.doi.org/10.1016/j.acra.2014.06.006
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demonstrated equal efficacy of aspiration versus suctionassisted FNA techniques (16,17). Visualization of the needle within the nodule along its long axis has been shown to improve diagnostic rates for deep nodules when compared with visualization along the needle’s short axis (18). Needle size seems to be relatively unimportant as studies comparing needles from 21 to 27 ga have not shown a diagnostic advantage of the larger bore needles (18–20). One small study showed no difference in ND rates between an experienced attending radiologist and a new attending radiologist (21). Another study examining attending pathologists’ interpretations of thyroid FNA based on number of years of experience found that less experienced pathologists were more likely to interpret samples as ND or atypical, whereas more experienced pathologists were more likely to interpret samples as benign (22). To our knowledge, the effect of resident training level on ND thyroid FNA rates is unknown. The aim of this study was to determine whether the diagnostic yield of thyroid FNA changes over the course of residency training.
Academic Radiology, Vol 21, No 11, November 2014
RESIDENT EXPERIENCE DECREASES ND RATE OF FNA
TABLE 1. ND FNA Rates by Level of Training, Comparing Residents with and without Prior Surgical Training, and Whether They Completed a Subsequent Interventional Radiology Fellowship ND Rate (%) Level of Training PGY2 PGY3 PGY4 PGY5
Surgery (95% CI)
No Surgery (95% CI)
Interventional Radiology (95% CI)
No Interventional Radiology (95% CI)
14.7 (10.5–20.2) 15.3 (10.3–22.0) 9.9 (5.2–18.1) 13.3 (9.0–19.1)
18.2 (15.6–21.3) 16.8 (14.4–19.6) 12.7 (10.2–15.6) 11.7 (9.1–14.8)
14.6 (11.1–19.0) 17.9 (13.2–23.9) 14.4 (9.4–21.3) 9.5 (6.0–14.7)
18.8 (16.0–22.0) 16.3 (13.8–19.2) 11.9 (9.5–14.8) 12.5 (9.8–15.8)
CI, confidence interval; FNA, fine-needle aspiration; ND, nondiagnostic; PGY, postgraduate year.
MATERIALS AND METHODS Through a search of our pathology departmental database (CoPath; Cerner Corporation, North Kansas City, MO), we identified 5418 nodules that underwent ultrasound-guided FNA in our radiology department between 2004 and 2012. Patients were 82.7% women, with an average age at biopsy of 54.8 15.4 years. All patients underwent a sonographic examination of the thyroid by an ultrasound technologist using high-frequency linear transducers (9–14 MHz; LOGIQ 9 and LOGIQ E9 ultrasound units; GE Healthcare, Wauwatosa, WI) before the requested FNA. Images were reviewed by an attending radiologist specializing in sonography. Ultrasound-guided FNAs were performed by a radiology resident under direct supervision of an attending radiologist. Standard FNA technique at our institution includes 1% buffered lidocaine for local anesthesia followed by five passes with 25- or 27-ga needles using capillary technique. The needle is monitored in real time for all passes using long-axis needle visualization. Samples were collected into 30-mL Cytolyt (Cytyc Corporation, Londonderry, NH) for processing in the cytology department after completion of the FNA. Standard thin sections were reviewed by an attending cytologist. Our cytology department uses standard sample adequacy criteria, which classify a sample ND if it has fewer than six groupings of at least 10 thyroid follicular cells each (23). The medical record was then reviewed and the following information was recorded: 1) the result of the FNA, classified as diagnostic or ND, 2) the resident and supervising attending who performed the FNA, and 3) the date the FNA was performed. Through review of our residency program’s records, the graduation year of each resident was used to determine the postgraduate year of training at the time of a given FNA. We also recorded if a resident had surgical residency training of at least 1 year before radiology residency and if a resident subsequently completed an interventional radiology fellowship. Generalized mixed modeling assuming a binominal distribution with classic sandwich estimation to adjust for any model misspecification was used to model diagnostic rate as a function of postgraduate year along with background in surgery or subsequent interventional radiology (SAS Software 9.3/PROC GLIMMIX; SAS Institute, Cary, NC). Multiple
Figure 1. Nondiagnostic thyroid fine-needle aspiration rate for residents with and without surgical training.
comparisons were examined using the Holm method with orthogonal linear contrasts. Statistical significance was predefined as P < .05. This study was Health Insurance Portability and Accountability Act compliant and received institutional review board approval.
RESULTS Of the 5418 thyroid FNAs performed in our radiology department, 3164 were performed by a resident under the direct supervision of an attending physician. Of the 74 residents, 8 (10.8%) were identified as having previous surgical training and 12 (16.2%) subsequently completed an interventional radiology training fellowship. It should be noted that five residents had both prior surgical and subsequent intervention radiology training. Results are summarized in Table 1. Mixed model examining residents with and without surgical training revealed a significant decrease in ND rate as postgraduate year increased (P = .0012). Moreover, post hoc follow-up analyses revealed a significant decrease in ND rate for residents without surgical training (P = .0007); conversely, no significant decrease was detected for residents with surgical training (P = .37; Fig 1). 1491
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Figure 2. Nondiagnostic thyroid fine-needle aspiration rate for residents who did and did not subsequently complete interventional radiology fellowship.
No significant difference was detected between the prior surgical and nonsurgical residents (P = .33). In addition, no significant difference was detected between postgraduate year 4 (PGY4) and PGY5 (P = .23). Likewise, a mixed model examining residents who did or did not subsequently complete an interventional radiology fellowship revealed an overall significant decrease in ND rate as postgraduate year increased (P = .0009). Post hoc follow-up analyses revealed a significant decrease in ND rate for residents not completing an interventional radiology fellowship (P = .0014), but for residents going on to interventional radiology fellowship, the decrease only approached significance (P = .08; Fig 2). Again, no significant difference was detected between residents with and without subsequent interventional radiology training (P = .94). In addition, the difference between PGY4 and PGY5 only approached significance (P = .08).
DISCUSSION To our knowledge, this is the only study to date examining how radiology resident seniority impacts diagnostic rates of thyroid FNA. We found that ND rates decreased as postgraduate year increased. This suggests that operator training and experience can have a significant effect on tissue sample adequacy. Our results support that early and continued performance of even simpler procedures such as thyroid FNA throughout residency training offers improved outcomes. This appears to be particularly true for residents who do not have prior surgical experience or interest in interventional radiology as evidenced by significant improvements in ND rates for residents without prior surgical training or not going on to complete an interventional radiology fellowship. The overall ND rate for thyroid FNA performed by radiology residents in this study was 15.3%, which is concordant with current literature (4–8). Prior studies have shown that multiple factors can improve the ND rate of thyroid
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FNA. For example, routine onsite cytopathology evaluation for adequacy has been shown to improve diagnostic rates (9–13). Recently, studies have assessed the ability of a cytopathology technician to determine sample adequacy and found no clinically significant difference between experienced cytopathology technician assessment and attending pathologist assessment (24,25). Furthermore, in one study, biopsies performed with cytopathology technicians were $464.10 less expensive than biopsies performed with attending pathologists (24). Prior studies have shown no significant difference in the yield of aspiration versus capillary technique, with the latter being standardly used at our institution (16,17). As recommended by the National Cancer Institute, we use 25- or 27-ga needles at our institution depending on attending preference with prior studies showing no significant difference in diagnostic yield between the two gauges (18,19,23). Finally, we perform thyroid FNAs using the long-axis technique which has been shown to improve diagnostic rates for deep nodules when compared to visualization along its short axis (18). Prior studies have examined the effect of radiology resident training year on preliminary interpretations of imaging studies. For example, Bruni et al. recently evaluated 5695 preliminary resident interpretations of neuroradiology studies and showed a nearly linear downward trend in the discrepancy rate with increasing resident training level (26). Another study of preliminary radiology resident interpretations in the emergency department found that the overall rate of reported discrepancies was low for all levels of training (0.23%–0.42 %) but did demonstrate a small, but statistically significant, decrease in the discrepancy rate for the senior residents (27). Based on their findings, the authors recommended that radiology resident training programs ensure that common discrepancies are specifically addressed as part of a dedicated emergency radiology course. However, another study performed after implementation of a dedicated emergency radiology course showed length of dedicated emergency radiology training before taking call made no significant difference. Of the variables assessed, only the resident training year showed a significant difference in scoring parameters (28). Effect of radiology training on performance of procedures is less well studied. A study in 2010 evaluated the complication rates and outcomes of 536 implanted subcutaneous chest ports placed by interventional radiology. They showed no significant difference in overall complication rates of ports placed between residents, physician extenders, fellows, and attendings (29). A more recent study found that when central venous catheters are placed by radiology residents, fluoroscopy time is double that for identical procedures performed by staff radiologists (30). They did not, however, demonstrate a linear correlation between fluoroscopy time and resident seniority, suggesting that increasing years of training for residents does not reduce the fluoroscopy time. The authors suggest that other factors such as fellowship training, increased awareness of radiation dose reduction tactics, or overall higher career procedure volumes may all contribute.
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Given our results demonstrating that a residents’ diagnostic yield improves over time, this may suggest a benefit to increased training in thyroid FNA technique perhaps using simulation phantoms of other methods of additional training early in residency. Training by simulation models has been described in radiology. Villard et al. developed a virtual simulator to teach liver biopsy through creation of a robust and real-time simulation environment combining a physical platform and an immersive computerized virtual environment (31). Meng et al. have described a picture archiving and communication system–integrated ultrasound-guided breast biopsy simulation exercise during radiology residency and found it increased residents’ procedural confidence and understanding of the American College of Radiology practice guideline for the performance of ultrasound-guided percutaneous breast interventional procedures (32). More hands-on interactive teaching devices have also been created, such as a device to teach residents pediatric intussusception reduction and a simulator to teach the Seldinger technique and angiography training (33,34). A current trend in medical resident training has been the development of simulation centers to provide an immersive training environment. One academic practice has utilized a simulation center to improve resident proficiency in multiple ultrasound-guided procedures (35). A potential limitation of our study is selection bias. However, generally nodules conceived as more difficult or more likely to be ND would be performed by a more experienced resident. The ultrasound department at our institution is staffed by both a junior and a senior resident. The larger more superficial solid nodules are preferentially biopsied by the more junior resident, whereas the smaller, cystic, or prior ND nodules are preferentially biopsied by the more senior resident. Therefore, if this bias affected our results, it could conceivably favor fewer ND results by the junior residents and decrease the differences between years of training. We do not use routine onsite cytology when performing thyroid FNA, which might have improved the diagnostic yield at all levels. An additional limitation is the lack of knowledge as to the level of attending involvement. For example, an attending may have felt that the sample acquired by the resident was inadequate or there were other difficulties in obtaining the FNA, and the attending may have therefore performed some of the passes themselves. However, again, this limitation would most likely lead to a smaller difference in the diagnostic yield between levels of training. Finally, Because of the retrospective nature of the study, we are unable to evaluate confounding factors such as patient body habitus, body mass index, or neck length as contributors to an ND biopsy as these were not recorded at time of initial FNA. In conclusion, senior radiology residents achieve significantly lower ND thyroid biopsy rates than junior residents, who may benefit from more intensive training in FNA technique early in their training. This benefit is most apparent in residents without a surgical background or strong interest in interventional radiology.
RESIDENT EXPERIENCE DECREASES ND RATE OF FNA
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