Practicability of using vaginal fluid markers in detecting premature rupture of membranes

Premature rupture of membranes (PROM) may cause intra-uterine infection and fetal death. A diagnostic tool that is non-invasive, specific and quick is needed to predict PROM. Human chorionic gonadotrophin (hCG), alpha-fetoprotein (AFP) and interleukin 6 (IL-6), which are present in vaginal fluid, were reported to be potential markers for PROM but have not yet been used in the clinic. This study was designed in a daily routine semi-emergency setting to evaluate the clinical practicability of using these markers in diagnosing PROM.

Using a random-access automated luminescence immunoassay system, 81 vaginal washing samples collected from third trimester pregnant women (43 from PROM patients, 38 from patients with intact membranes) were analysed for beta-hCG, AFP and IL-6 in a semi-emergency setting. The Mann-Whitney U-test was used to test the difference between the two groups. Receiver operator curve (ROC) analysis was used to evaluate the performance of the three markers and to determine the cut-off value for a positive diagnosis.

Vaginal fluid concentrations of the three markers were significantly different (P < 0.001) between the two groups. ROC analysis indicated that AFP had a 97.7% diagnostic sensitivity and 100% specificity; the other two markers had lower diagnostic sensitivity and specificity (95.3% and 89.5% for beta-hCG and 83.7% and 78.9% for IL-6, respectively).

This work demonstrates that, of the three markers investigated, AFP has the highest diagnostic sensitivity and specificity. Using the 'stat' function provided by the automated luminescence immunoassay system, the reporting time of the results was less than 1h. We conclude that vaginal fluid AFP measured by random-access automated luminescence immunoassay is an ideal marker for the diagnosis of PROM. The technique could be introduced into the laboratory as a semi-emergency service to meet clinical needs.