Fisk, N.M.

University of Queensland eSpace

Fisk, Dipstick test for infection in PPROM 565
J. Perinat. Med.
15 (1987) 565
A dipstick test for infection in preterm premature rupture of the
membranes
Nicholas M. Fisk
Department of Obstetrics and Gynecology, King George V Hospital, Royal Prince
Alfred Hospital, Sydney, Australia
1 Introduction
Conservative management regimes are increas-
ingly used in preterm premature rupture of the
membranes (PPROM), [16] following the recogni-
tion that perinatal deaths from prematurity exceed
those from infection [1, 7]. Amniocentesis has
been suggested in patients managed expectantly
to reduce the remaining risk of infectious morbid-
ity, by allowing early identification and delivery
of patients with colonized liquor [9,10]. Although
ruptured membranes have previously been consid-
ered a contraindication to amniocentesis, the tech-
nique is successful in up to 70% in yielding uncon-
taminated liquor for microbiological analysis [4,
6,9].
As standard cultures require 24—48 hours and
laboratory services in most institutions are limited
at night, a need exists for a rapid analysis that
can be performed by the obstetrician. A dipstick
which predicts the presence of leukocytes, is evalu-
ated in this study for use in amniotic fluid.
2 Patients and methods
Twenty-five women with PPROM at gestational
weeks ranging from 26 to 34 were entered into
the study. An obvious pool of liquor was demon-
strated in the posterior fornix of each on speculum
examination. Patients were not in labor, had no
clinical evidence of infection, and were not on
antibiotics. All were considered suitable for con-
servative expectant management. Real time ultra-
sound identified accessible liquor pockets in 23,
Curriculum vitae
NICHOLAS FISK was bom
in 1956 in Australia. He
graduated from the Univer-
sity of Sydney in 1980 and
underwent his specialist
training at King George V
Hospital in Sydney. In
1983 he worked in the King
Edward VIII Hospital in
South Africa, and is cur-
rently a lecturer in the De-
partment of Obstetrics and
Gynecology at the University of Aberdeen, Scotland. His
main interests are preterm labor and antenatal diagnosis.
in whom transabdominal amniocentesis was at-
tempted. An aseptic technique with povidone-iod-
ine skin preparation was employed. No specimen
was obtained in 3 despite two passages of the
needle. Twenty-one samples were obtained from
20 patients (1 with diamnionic twins). Each sam-
ple was separated into two fractions: into one
of 3 ml, the test strip ("Cytur-test", Boehringer
Mannheim, GmbH) was dipped and read at 15
minutes, while microscopy and culture was per-
formed in aerobic, anaerobic and mycoplasmal
media on the other. In the presence of leukocytes,
indoxyl ester in the white test strip is cleaved
by granulocytic esterases to yield indoxyl, which
oxidizes in air to the blue dye indigo. One heavily
blood contaminated specimen stained the test
strip, obscuring interpretation of color change and
was excluded. Microscopy was omitted in two.
1987 by Walter de Gruyter & Co. Berlin · New York
566 Fisk, Dipstick test for infection in PPROM
3 Results
Amniocentesis was successful in yielding liquor in
20 of the 23 (86.9%) patients on whom it was
attempted. Overall, liquor samples were obtained
in 20 of the 25 patients (80%) with PPROM. In
7 of the samples, the dipstick read > 25 leukocytes
per μΐ, whilst uncentrifuged microscopy demon-
strated significant leukocytes (> 2 leukocytes per
oil immersion field χ 1,000) in 5. A micro-organ-
ism was cultured (> 103 colonies per ml) in 6
specimens. As a predictor of a positive culture,
the test strip gave one false negative and two false
positives, whilst microscopy produced one of each
(figure 1). Both tests yielded similar sensitivities
and specificities (table I). Each proved less predic-
tive of histological acute diffuse chorioamnionitis
10
CYTUR
14
MICRO
13
Negative test
Positive test
NEGATIVE CULTURE POSITIVE CULTURE
Figure 1. Presence or absence of leukocytes as predicted
by the "Cytur-test" (CYTUR) or microscopy (MICRO)
in patients with and without an organism on liquor
culture.
(using a membrane roll technique [3]) due to 6
patients with a negative culture and positive histo-
logy. All these delivered > 48 hours after amni-
ocentesis, suggesting that infection complicated
rather than caused their PPROM. All patients
with both positive dipstick and microscopy had a
positive culture and histological confirmation of
infection, whereas the 10 with both tests negative
had sterile liquor.
4 Discussion
Microscopy, Gram stain, and culture of amniotic
fluid obtained by amniocentesis in PPROM are
known to have predictive value for chorioamnion-
itis [4, 6, 10, 11, 15, 23]. Liquor culture improved
5 minutes Apgar when intervention is based on a
positive result. Nevertheless a role remains for
slightly less accurate but more rapid investigation,
especially where immediate decisions on manage-
ment, such as tocolysis, are needed. The Cytur-
test, which detects leukocytic esterases, was in-
itially designed for use in urine [2], but has also
been used in peritoneal dialysate [5] and seminal
fluid [17]. This pilot study suggests that the
dipstick test is as accurate as microscopy in pre-
dicting colonized liquor, yielding similar sensitivi-
ties (83% and 80% respectively) and specificities
(86% and 92%). The advantage of the dipstick,
however, is that it can be performed simply and
rapidly at the bedside by the obstetrician. These
accuracies were improved further by combining
both tests, so that a positive dipstick and micro-
scopy was 100% specific and positively predictive
from the limited numbers in this study, while
either test positive proved 100% sensitive and
negatively predictive of a positive culture. Al-
though other predictors of infection have been
suggested in PPROM, such as biophysical profiles
[18], fetal breathing [20], gas liquid chromatogra-
Table I. Accuracy of dipstick and microscopy for polymorphs as predictors of a positive liquor culture.
Sensitivity
Specificity
Positive predictive value
Negative predictive value
Dipstick
83.3%
85.7%
71.4%
92.3%
Microscopy
80%
92.3%
80%
92.3%
Dipstick and
microscopy
60%
100%
100%
86.7%
Dipstick or
microscopy
100%
76.9%
62.5%
100%
J. Perinat. Med. 15(1987)
Fisk, Dipstick test for infection in PPROM 567
phy [13], liquor volume [12], C-reactive protein [8]
and cardiotocography [19] none have been shown
superior to liquor culture [14, 21, 22]. The Cytur-
test merely aids in the rapid prediction of a posi-
tive culture, and is not suggested as an alternative
predictor of chorioamnionitis.
Summary
Microbiological analysis of amniotic fluid obtained by
amniocentesis is increasingly employed in preterm pre-
mature rupture of the membranes (PPROM) to predict
those patients at increased risk of chorioamnionitis. Al-
though liquor culture appears the most accurate predic-
tor, a role exists for rapid but slightly less accurate
testing. In this study, a dipstick (Cytur-test) which pre-
dicts the presence of leukocytes was evaluated in amni-
otic fluid. Twenty-one samples were obtained by amni-
ocentesis from 25 women with PPROM at gestation
26 — 34 weeks. The dipstick predicted 5 out of 6 speci-
mens with a positive culture and 12 of 14 with a negative
culture (figure 1). Its accuracy as a predictor of a positive
culture was similar to microscopy for polymorphs, with
sensitivities of 83.3% and 80% respectively and specifici-
ties of 85.7% and 92.3%. Neither test proved as predic-
tive of histological chorioamnionitis due to 6 patients
delivering > 48 hours after amniocentesis who may have
developed infection subsequent to the demonstration of
sterile liquor.
Keywords: Amniocentesis, chorioamnionitis, fetal membranes, premature rupture, preterm labor, PPROM.
Ein Teststreifen zur Diagnostik des Amnioninfektionssyn-
droms bei vorzeitigem Blasensprung
Die mikrobiologische Analyse von durch Amniozentese
gewonnenem Fruchtwasser wird zunehmend zur frühzei-
tigen Diagnose des Amnioninfektionssyndroms bei vor-
zeitigem Blasensprung angewandt. Obwohl die Frucht-
wasserkultur die exaktesten Analysen ermöglicht, be-
steht eine Nachfrage für einen weniger exakten, dafür
aber schnelleren Test. In dieser Studie wurde ein Test-
streifen (Cytur-Test), der auf Leukozyten anspricht, in
Fruchtwasser erprobt. 21 Proben wurden mittels Amnio-
zentese von 25 Frauen mit vorzeitigem Blasensprung in
der 26. —34. Woche gewonnen. Der Teststreifen korre-
Schlüsselwörter: Amniozentese, Amnioninfektionssyndrom, Fruchtblase, vorzeitiger Blasensprung, vorzeitige We-
hen.
lierte in 5 von 6 Proben mit einer positiven Kultur, und
in 12 von 14 Proben mit einer negativen Kultur (Abb. 1).
Seine Genauigkeit zur Voraussage einer positiven Kultur
entsprach der einer mikroskopischen Untersuchung auf
Polymorphien mit einer Empfindlichkeit von 83,3%
bzw. 80% und einer Spezifität von 85,7% bzw. 92,3%.
Keiner der beiden Tests zeigte eine histologische Frucht-
blasenentzündung an, die bei sechs Frauen gefunden
wurden, die mehr als 48 Stunden nach der Amniozentese
ihre Kinder bekamen. Bei diesen Frauen könnte sich
eine Infektion nach dem Nachweis eines sterilen Frucht-
wassers entwickelt haben.
Resume
Batonnets diagnostiques d'infection dans la rupture prema-
turee des membranes
On utilise de plus en plus Fanalyse microbiologique du
liquide amniotique obtenu par amniocentese an cas de
rupture prematuree des membranes (RPM) pour predire
quelles patientes seront ä risque eleve de chorioamnio-
tite. Bien que la mise en culture du liquide apparaisse
comme 1'element predictif le plus approprie, il existe une
place pour des tests rapides mais un peu moins fiables.
Dans cette etude nous avons evalue la valeur de baton-
nets reactifs (cytur-test) qui predisent la presence de
leucocytes, au niveau du liquide amniotique. Vingt et
un prelevements ont etc obtenus chez 25 femmes avec
RPM ä 26 —34 semaines gestationnelles. Les batonnets
ont ete positifs pour 5 des 6 liquides dont la culture etait
positive et negatifs pour 12 des 14 liquides dont la
culture etait negative (figure 1). La fiabilite des baton-
nets comme predicteur d'une culture positive est simi-
laire ä Fexamen au microscope, avec une sensibilite
respectivement de 83,3% et de 80% et une specificite de
85,7% et de 92,3%. Aucun des tests n'a prouve une
valeur predictive pour une chorioamniotite histologique
secondaire chez 6 patientes ayant accouche plus de 48
heures apres l'amniocentese et qui ont presente une
infection secondaire alors que le liquide amniotique etait
sterile.
Mots-cles: Accouchement premature, amniocentese, chorioamniotite, membranes fcetales, R. P. M., rupture prema-
turee.
Acknowledgements: The author gratefully acknowledges Dr. R. BENN for assistance with the microbiological
studies, Dr. P. RUSSELL for the placental pathology and Drs. A. BRADFIELD and A. CHILD for
their encouragement.
J. Perinat. Med. 15(1987)
568 Fisk, Dipstick test for infection in PPROM
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Received November 14, 1986. Revised February 3,
1987. Accepted February 10, 1987.
Dr. Nicholas M. Fisk
RPMS Institute of Obstetrics & Gynecology
Queen Charlotte's Maternity Hospital
Goldhawk Rd
London W6 OXG
United Kingdom
J.Perinat. Med. 15(1987)


A Dipstick Test for Infection in Preterm Premature Rupture of the Membranes

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A Dipstick Test for Infection in Preterm Premature Rupture of the Membranes

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