M. de Diego, M. Marcos, J. Burgos, D. Rando, J. C. Melchor, I. Melchor, A. Iza, H. Navas
To assess the performance of the PAMG-1 and fFN tests using real-world data for the prediction of spontaneous preterm delivery (sPTD) in patients presenting to an emergency obstetrical unit with threatened preterm labour (PTL) by conducting a retrospective audit of patient medical records over two different one-year time periods during which either fFN or PAMG-1 was used as the standard of care biochemical test.
A retrospective cohort study chart review of women with threatened PTL electronic medical records (EMR) from a Level III maternity hospital was conducted for two periods of one year each: (1) the “Baseline” time period, during which the qualitative fFN test with a cutoff of 50 ng/ml was used as standard of care biochemical test for the risk assessment of preterm delivery, and (2) the “Comparative” time period, during which the PAMG-1 test with a cutoff of 1 ng/mL was used as the standard of care biomarker test. Patients with singleton gestations between 24+0 to 34+6 weeks of gestation with symptoms of early preterm labour, clinically intact membranes, and cervical dilation <3 cm, who did not have a medically-indicated preterm delivery within 14 days of testing were selected for chart review and included in the analysis. Key parameters used for analysis were biochemical test results, time of testing, and time of delivery. Positive predictive value (PPV), negative predictive value (NPV), sensitivity (SN), specificity (SP), and likelihood ratios (LR+ and LR-) for the prediction of sPTD ≤7 and ≤14 days were calculated for PAMG-1 and fFN.
420 patients were identified in the EMR as having presented with threatened PTL during the Baseline period. 90.0% (378/420) subjects met eligibility criteria, 10.1% (38/378) of which were fFN positive and 2.6% (10/378) of which had a sPTD ≤7 days. fFN PPV and NPV were 7.9% and 97.9% for sPTD ≤7 days, respectively. fFN LR+ and LR- were 3.15 and 0.77, respectively. 410 patients were identified in the EMR as having presented with threatened PTL during the Comparative period. 89.5% (367/410) subjects met eligibility criteria, 4.6% (17/367) of which were PAMG-1 positive and 3.3% (12/367) of which had a sPTD ≤7 days. PAMG-1 PPV and NPV were 35.3% and 98.3% for sPTD ≤7 days, respectively. PAMG-1 LR+ and LR- were 16.14 and 0.52, respectively.
Before switching to PAMG-1 for the risk assessment of spontaneous preterm delivery, fFN was our standard of care test. Our retrospective audit of each test's performance over separate one-year periods shows that we were over 2 times more likely to get a positive fFN test than a PAMG-1 test, and that our rate of discharging women who ultimately delivered spontaneously within 14 days of testing was not impacted. Furthermore, a positive PAMG-1 test was >4 times more reliable than a positive fFN test in predicting imminent sPTD. Fewer positive biomarker test results that are more reliable is associated with a reduction in unnecessary admissions, avoidable treatments, and preventable use of hospital resources.