VALUE OF THE FERN TEST TO CONFIRM OR REJECT THE DIAGNOSIS OF RUPTUREDMEMBRANES IS MODEST IN NONLABORING WOMEN PRESENTING WITH NONSPECIFIC VAGINAL FLUID LOSS

The strength of the fern test to differentiate between amniotic and no namniotic fluid in vaginal discharge was determined in 51 term women i n labor with ruptured membranes and compared with that in a group of 1 20 nonlaboring subjects, presenting with nonspecific vaginal fluid los s. Sensitivity and specificity in the laboring group were 98.0 and 88. 2%, respectively, in agreement with previous reports. In contrast, in the nonlaboring group sensitivity and specificity were only 51.4 and 7 0.8%, respectively. The result of the fern test predicted the actual s tate of the membranes correctly in 63% and incorrectly in 29% of these patients. In 16 or 39 subjects with ruptured membranes (approximately 40%), the outcome of the fern test was negative. The modest diagnosti c strength of the fern test in the present study compared with previou sly reported data is at least in part due to differences in study popu lation (laboring versus nonlaboring) and to the fact that observers we re deprived of relevant clinical information. It is concluded that the fern test should be granted supportive rather than conclusive value i n diagnosing ruptured membranes in nonlaboring women presenting with n onspecific vaginal fluid loss.