[Evaluation of 3 diagnostic methods in premature rupture of membranes: diamine-oxidase assay, alpha-fetoprotein assay, colorimetric method evaluating the pH].

The authors set out to assess the three diagnostic methods available which can detect early breaking of the membranes: radio-enzymatic assay of diamine-oxidase (DAO), radioenzymatic assay of alpha-fetoprotein (AFP), colorimetric method for determining pH (Amnicator). Between June 1991 and March 1992, 114 samples of vaginal secretions were taken from 104 pregnant patients being followed up at Maternity Unit A, Bordeaux (France). The results of the assays were expressed in quantitative terms (microU/ml for DAO and ng/ml for AFP); ROC (Receiver Operating Characteristic) curves were used to determine the positivity threshold in terms of the sensitivity and specificity (20 microU/ml for DAO and 15 ng/ml for AFP). The sensitivity of the pH test was 97.5%, which was significantly better than that of DAO (90.2%) and even that of AFP (82.9%). However, there was no difference between the specificities of the pH, DAO and AFP tests (93.3%, 96.6% and 93.5% respectively). The data were compared with those in the literature. The problems in collecting the vaginal secretions probably accounts for the better results of the colorimetric test. This is a reliable, fast and easily reproducible test; these qualities make it the preferred test in EBM, and it can be completed using a radioenzymatic method (DAO) or immunoradiometric test (AFP).