Which test is NOT used to diagnose premature rupture of membranes?

The correct answer is a blood test for hCG levels. This test is typically used to evaluate pregnancy status, confirming whether a woman is pregnant or not, but it does not provide information regarding the current status of membranes or the presence of amniotic fluid. Diagnosing premature rupture of membranes (PROM) relies on specific assessments that directly indicate the rupture and leakage of amniotic fluid.

The pooling test on a speculum exam is a direct examination method for identifying fluid in the vaginal canal, which can indicate PROM. The amniotic fluid index measurement via ultrasound helps assess the amount of amniotic fluid, which can be low if the membranes have ruptured. The Nitrazine paper test checks the pH of vaginal secretions; amniotic fluid has a higher pH than normal vaginal secretions, so a positive test suggests the presence of amniotic fluid, corroborating PROM.

Each of these methods is aimed at directly assessing membrane integrity or the status of amniotic fluid, whereas the hCG blood test serves a different purpose and does not provide direct information about PROM.