Use of Noninvasive PAMG-1 Is Cost-Beneficial in Certain Situations

Clinical scenario: A patient who is 32 weeks pregnant presents with possible leakage of amniotic fluid, but her description of the leakage as well as the results of the combined traditional diagnostic test (CTDT) of pooling, nitrazine, and ferning are inconclusive. A more definitive test would be great, especially a noninvasive test, but your institution doesn’t use the very sensitive and very specific placental alpha-microglobulin-1 test (PAMG-1) because it’s too expensive (estimates of $85.76 vs $14.30 for CTDT). But delivering an infant preterm, especially unnecessarily, is costly too.

Nelson C. Echebiri, MD, MBA, a junior fellow of ob/gyn at the University of Buffalo, NY, described this scenario while presenting a Donald F. Richardson Memorial Prize Paper at the 2014 ACOG Annual Clinical Meeting in Chicago on Tuesday. He explained that this study came to pass when he encountered just such a situation. He then started to wonder about whether use of the PAMG-1 would be a cost-beneficial screening strategy for potential preterm premature rupture of membranes (PPROM), considering that the average first-year cost associated with a preterm delivery is about $47,000.

There wasn’t any data that offered him insights, so he, along with several colleagues, constructed a decision analysis model to estimate the cost benefit of PAMG-1 compared with CTDT on preterm delivery costs from a societal perspective. They used a scenario of a PPROM occurring between 34 and less than 37 weeks’ gestation, with cost estimates reflecting 2013 US dollars. This gestational age is important because ACOG currently recommends delivery when PROM is diagnosed between 34 and less than 37 weeks’ gestation. Although ACOG also says that expectant management can be considered, most institutions don’t support expectant management for PROM, Echebiri explained.

What Echebiri and colleagues found was that use of PAMG-1 was associated with an estimated annual net benefit of $12,215 per person tested, compared with a net benefit associated with CTDT use of $4,727 per person tested. They determined that if the probability of rupture is less than 42%, then use of the PAMG-1 is cost-beneficial, with a net savings of $5,000 to $32,000 per person tested; the net savings of CTDT in a similar scenario would be $5,000 to $9,000 per person tested. However, if the probability of rupture is greater than 44%, use of PAMG-1 will not generate any net savings.

He concluded that PAMG-1 is the most optimal diagnostic method both economically and clinically for the diagnosis of PROM in uncertain presentations and when CTDT is inconclusive or ambiguous. Echebiri emphasized that use of PAMG-1 is not a test-all approach. Since probability of PROM needs to be less than 42% for PAMG-1 to have a cost benefit, clinicians will have to weigh the odss when determining the appropriateness of using this test.

For context, Echebiri asked this: If a patient presents at 34 weeks and 2 days with PPROM but has an ambiguous explanation of the scenario regarding fluid leakage (eg, she was sitting down and had to use the bathroom; when she stood up, she felt some fluid leaking-trickling, not a gush) and you had to determine if her membranes had ruptured, knowing full well that you’d have to deliver if they had, which test would you prefer to use?