COMPARING THE IMMUNOASSAY OF PLACENTAL ALPHA-MICROGLOBULIN-1 WITH STANDARD METHODS IN THE DIAGNOSIS OF PRELABOUR RUPTURE OF FETAL MEMBRANES IN LAGOS

Abstract

Background: Prelabor rupture of membranes is a common obstetric complication which
present with some diagnostic challenge especially in equivocal cases. Standard methods of
diagnosis had relied on history and clinical examination with the demonstration of pooling of
liquor or its egress from the cervical os on speculum examination. These methods (including
nitrazine and fern test) are however, limited by high false positives and negatives. In the
absence of a non-invasive gold standard for diagnosis, several rapid, less invasive methods of
diagnosis are being developed based on the demonstration of biomarkers with high
concentrations in amniotic fluid, with increased levels observed in cervicovaginal fluids only
with fetal membrane rupture. This study therefore compared the accuracy of these traditional
methods and placental alpha microglobulin-1.
Objective: To compare the accuracy of placental alpha-microglobulin-1 (PAMG-1) in
cervicovaginal secretions with that of other standard methods in the diagnosis of prelabour
rupture of membranes.
Methodology: A longitudinal study from March to November 2011 conducted in women with
symptoms and signs of prelabor rupture of fetal membranes. Standard diagnostic methods were
carried out and in addition findings at PAMG-1 assay using the Amnisure ROM test were
compared with the reported final diagnosis at delivery. The final diagnosis of membrane
rupture was definitively made upon review of medical records after delivery and thereafter
used to determine false positives and negatives. Descriptive analysis was done using Statistical
Package for Social Sciences (SPSS) version 19.
Results: A total of 140 consenting pregnant women were recruited. An initial diagnosis of
PROM was made in 67 patients (47.9%) using the standard methods of diagnosis while PAMG
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1 immunoassay using Amnisure ROM test diagnosed PROM in 86 patients (61.4%). Upon
review of patients’ clinical records, 88 women (62.8%) had a final diagnosis of PROM while
52 patients (37.2%) had intact membranes. Discrepancies between PAMG-1 and the standard
methods were observed in 21 cases. In the final analysis, PAMG-1 assay had a sensitivity of
97.7%, specificity 100%, positive predictive value 100% and negative predictive value 96.7%.
The standard methods had a sensitivity 76.1%, specificity 92.2%, positive predictive value
90.1% and negative predictive value 70.4%. There were 2 false negative results with PAMG
1. It however, had a higher accuracy of 98.6%, followed by nitrazine test 89.3%, pooling of
liquor 83.5% and fern test 51.4%.
Conclusion: The immunoassay of PAMG-1 had a higher diagnostic accuracy than other
standard diagnostic methods and is recommended for the diagnosis of prelabor rupture of fetal
membranes.

COMPARING THE IMMUNOASSAY OF PLACENTAL ALPHA-MICROGLOBULIN-1 WITH STANDARD METHODS IN THE DIAGNOSIS OF PRELABOUR RUPTURE OF FETAL MEMBRANES IN LAGOS