AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 7, NUMBER 2

April 1990

LEUKOCYTE ESTERASE ACTIVITY IN AMNIOTIC FLUID: NORMAL VALUES DURING PREGNANCY Iffath Abbasi Hoskins, M.D., Frances Marks, M.D., Steven Anthony Ordorica, M.D., and Bruce Kenneth Young, M.D.

Chorioamnionitis during pregnancy is a common diagnostic dilemma for the obstetrician. Fast and accurate diagnosis poses the most significant problem. Since leukocytes are known to be released in response to infections, examination of amniotic fluid for their presence is an important part of the evaluation for chorioamnionitis. These neutrophils contain several esterases that are not present in serum, urine, or vaginal secretions. The esterases are not influenced by bacteria or by commonly used drugs. We have previously described the reliability of leukocyte esterase (LE) activity for the detection of chorioamnionitis in term pregnancies uncomplicated by other diseases. A prospective study was performed to assess the presence or absence of LE activity to establish normal values in amniotic fluid at various gestational ages prior to term before its use as a possible predictor for chorioamnionitis. Sterile amniotic fluid specimens were obtained from 13 patients undergoing second trimester genetic amniocentesis (with gestational ages varying from 15 to 19 weeks) and from 11 patients with a wide variety of medical problems, undergoing amniocentesis for Rh sensitization or lung maturation studies (with gestational ages ranging from 25 to 27 weeks). All patients with ruptured membranes or preterm labor were excluded. Each amniotic fluid sample was divided into two parts, one of which was transported to the laboratory for aerobic and anaerobic cultures and the other used for LE activity detection as measured by dipstick. The LE results were retrospectively compared with the results of the cultures. LE activity was always found to be negative when the culture results were negative. On the basis of this study, we have established the norms for LE activity in amniotic fluid prior to term, even in the presence of other medical or obstetric complications.

Chorioamnionitis during pregnancy is a common diagnostic dilemma for the obstetrician. Rapid and accurate diagnosis poses the most significant problem. The clinical diagnosis is usually based on a syndrome of fever, maternal or fetal tachycardia, uterine tenderness, foul odor of the amniotic fluid and peripheral blood leukocytosis, but there is uncertainty regarding early diagnosis and laboratory confirmation.l Since leukocytes are known to be released in response to infections, examination of the amniotic fluid for their presence may prove to be useful in the evaluation for chorioamnionitis. Neutrophilic leukocytes contain several esterases that are not present in serum, urine, or body tissues.2"4 Leukocyte esterase chemstrips (Chemstrip 9, Biodynamics) are now readily available and have been

frequently used for the detection and semiquantitation of leukocytes in urine. 56 This test strip detects the presence of a leukocyte esterase, which catalyzes the hydrolysis of an indoxyl carboxylic acid ester to indoxyl. The indoxyl reacts with a diazonium salt to produce a purple color6 (Fig. 1). The esterase activity measured by the assay does not require intact cells and is not affected by changes in amniotic fluid pH, cells, protein, or bacterial contents. We have previously described the reliability of leukocyte esterase activity in the rapid detection of urinary tract infections7 in obstetric patients and for the detection of chorioamnionitis in term pregnancies uncomplicated by other diseases.8 A prospective study was performed to assess the presence or absence of leukocyte esterase activity to establish nor-

Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, New York UniversityBellevue Medical Center, New York, New York Reprint requests: Dr. Hoskins, Department of Obstetrics and Gynecology, NYU-Bellevue Medical Center, 450 First Avenue, Room 9N1, New York, NY 10016

130

Copyright © 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.

Downloaded by: NYU. Copyrighted material.

ABSTRACT

LEUKOCYTE ESTERASE ACTIVITY IN NORMAL PREGNANCY/Hoskins et al.

Figure 1 . The chemical reaction involved in the detection of leukocyte esterase activity.

mal values in amniotic fluid at various gestational ages prior to term before its use as a possible predictor for chorioamnionitis.

Leukocyte esterase activity was always absent in the uninfected amniotic fluids in both groups I and II, that is, at all gestational ages prior to term. Leukocyte esterase activity was also absent in the samples obtained from pregnancies complicated by medical diagnoses, such as Rh sensitization, diabetes mellitus, polyhydramnios. The cultures obtained from these samples were always found to be negative, whenever the leukocyte esterase activity detection was read as negative or trace from the color chart with use of the manufacturers' specifications (Table 2). COMMENT

MATERIALS AND METHODS

RESULTS

Table 1 represents a cross-tabulation of the leukocyte esterase detection and the culture results.

Acute chorioamnionitis complicating pregnancy continues to pose a major threat for the patient and her fetus. However, at present there are no optimal diagnostic criteria specific for its diagnosis. All reports in the literature show poor correlation of the various parameters for the prediction of infection. We7 have previously reported on the reliability of leukocyte esterase activity detection in amniotic fluid (sensitivity 91%, specificity 95%) for the diagnosis of chorioamnionitis at term. We found it to be superior to the reliability of amniotic fluid cultures (sensitivity 86%, specificity 91%) or Gram's stains (sensitivity 62%, specificity 81%) for diagnosing amniotic fluid infections. However, prior to establishing its use as a reliable screening test for chorioamnionitis, we present our findings in which the absence of leukocyte esterase activity always predicted a negative culture. This test can be utilized at all gestational ages and the detection of its activity is unaffected by maternal medical and obstetric complications, thus establishing its usefulness as a specific predictor for amniotic fluid infections. Its usefulness is further enhanced by the simplicity of its use. The required training to perform the test is minimal. It is clinically reproducible. The results are obtained within 1 to 2 minutes.

Downloaded by: NYU. Copyrighted material.

Sterile amniotic fluid specimens were obtained from 24 antepartum patients undergoing amniocenteses. After the absence of clinical infections was ascertained, each patient was assigned to either group I (gestational ages between 15 and 19 weeks) or to group II (gestational ages between 25 and 34 weeks). Indications for the amniocenteses included genetic studies, rhesus isoimmunization, diabetes mellitus, and uncertain dates (Table 1). All patients with premature rupture of membranes or preterm labor were excluded. Each amniotic fluid sample was divided into two parts, one used for leukocyte esterase activity detection and the other transported to the laboratory for aerobic and anaerobic cultures. The leukocyte esterase activity was determined by dipping the dipstick in the fluid, then comparing the color reaction with the color chart after 1 minute. Positive cultures were denned as the presence of organisms greater than 104 cfu/ml.

Table 1. Cross-Tabulation of Leukocyte Esterase Activity and Culture Results Leukocyte Esterase Activity Group I (GA* 15 to 19 weeks) Genetic Amniocentesis (13) Group II (GA 2 5 - 3 7 weeks) Polyhydramnios (2) Rhesus isoimmunization (2) Diabetes mellitus (3) Uncertain dates (4) *GA: gestational age.

Table 2. Results of Leukocyte Esterase Tests Compared with the Culture Results Cultures Group

Negative

Negative

Negative Negative Negative Negative

Negative Negative Negative Negative

Leukocyte Esterase Test Results

Cultures

Negative Trace

Negative Negative

Negative Trace

Negative Negative

I (GA* 15-19 weeks)

9 4 II (GA 2 5 - 3 7 weeks)

7 4 *GA: gestational age.

131

AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 7, NUMBER 2 REFERENCES

strip L. J Urol 125:388, 1981 6. Kusumi RK, Grover PJ, Kunin CM: Rapid detection of pyuria by leukocyte esterase activity. JAMA 245:1653, 1981 7. Abbasi IA, Hess LW, Johnson TRB, McFadden E, Chernow B: Leukocyte esterase activity in the rapid detection of urinary tract and lower genital tract infections in obstetric patients. Am J Perinatol 2:311, 1985 8. Hoskins Abbasi I, Johnson TRB, Winkel CA: Leukocyte esterase activity in human amniotic fluid for the rapid detection of chorioamnionitis. Am J Obstet Gynecol 157: 730, 1987

Downloaded by: NYU. Copyrighted material.

1. Gibbs RS, Castillo MS, Rodgers PJ: Management of acute chorioamnionitis. Am J Obstet Gynecol 136:709, 1980 2. Chemstrip 9, Biodynamics, package insert 3. Rindler-Ludwig R, Schmalzl F, Braunsteiner H: Esterases in human neutrophil granulocytes: Evidence for their protease nature. Br J Haematol 27:57, 1974 4. Li CY, Lam KW, Yam LT: Esterases in human leukocytes. J Histochem Cytochem 21:1, 1973 5. Gillenwater JY: Detection of urinary leukocytes by Chem-

April 1990

132

Leukocyte esterase activity in amniotic fluid: normal values during pregnancy.

Chorioamnionitis during pregnancy is a common diagnostic dilemma for the obstetrician. Fast and accurate diagnosis poses the most significant problem...
572KB Sizes 0 Downloads 0 Views