Premature rupture of the membranes: analytical evaluation of diagnostic tests

Premature rupture of the membranes (PROM) is a frequent event affecting 3% of pregnancies. PROM causes 30% of premature deliveries and 20% of perinatal mortality. The diagnosis relies mainly on the clinical visualization of the amniotic fluid flow in the vagina. If not, clinicians can use bedside tests detecting either the change of the vaginal pH or the presence of amniotic components mainly IGFBP-1 or AFP in the vaginal fluid. We aimed to study the technical and analytical characteristics of 5 immunochromatographic tests (easyProm®, ActimProm®, Toda Amniodiag 5 strip®, Amnioquick® Duo, Amnisure®) that mainly detect IGFBP-1 in order to compare our results with the data from the manufacturer. We evaluated the pre-analytical phase (sampling, sample stability and elution) and the analytical phase (limit of detection, reading time and interferences related to a physiological contamination). Compliance with the pre-analytical step is crucial because the absorption and the elution of the samples in the buffer vary with the swab. Once eluted, the sample is stable. The recommended reading times are adequate but must not be exceeded, otherwise the result can be falsely positive. The detection limits announced appear to be to optimistic. The presence of maternal blood but not maternal urine can perturb the results.