Nikolova T, et al. – Investigators compared placental alpha microglobulin-1 (PAMG-1) test and the phosphorylated insulin-like growth factor-binding protein-1 (phIGFBP-1)-1 test alone and in combination with cervical length measurement for the prediction of imminent spontaneous preterm birth of testing in pregnant women with symptoms of preterm labor in a tertiary care setting. Findings indicated that PAMG-1 is a better predictor of imminent spontaneous preterm birth vs phIGFBP-1 alone or in combination with cervical length measurement. In patients with shortening of cervical length between 15 and 30 mm, the PMAG-1 test is a significantly better predictor of imminent spontaneous preterm birth within 7 days of testing vs phIGFBP-1.

Methods

• Researchers prospectively recruited 403 patients with intact amniotic membranes and cervical dilation ≤3 cm, without recent intercourse or cerclage, between gestational weeks of 20⁺⁰ and 36⁺⁶ from three international centers.
• They conducted PAMG-1 and phIGFBP-1 tests prior to cervical length measurement via transvaginal ultrasound.
• They blinded the caregivers to the biomarker test results.
• Researchers excluded the medically indicated deliveries within 14 days of testing.
• They calculated standard performance statistics with 95% confidence intervals and compared based on pairwise estimates from a generalized model.

Results

• Of the 403 individuals enrolled in the study, cohort inclusion criteria were met by 94% (383/403).
• Findings suggested the median gestational age and cervical length at presentation to be 30⁺⁵weeks and 27 mm, respectively.
• Spontaneous birth ≤ 7 days from testing were seen in 6.8% (26/383) of women.
• In 7.8% (30/383) women, PAMG-1 test was positive, whereas phIGFBP-1 test was positive in 29.5% (113/383).
• In the overall cohort, positive predictive value for PAMG-1, phIGFBP-1, and cervical length < 25 mm for prediction of spontaneous preterm birth was 60.0% (18/30), 18.6% (21/113), 11.8% (18/152), respectively.
• Results demonstrated the negative predictive value to be 97.7% (345/353), 98.2% (265/270), 96.5% (223/231), respectively.
• In this group, the prevalence spontaneous preterm birth was 6.8% (26/383).
• Experts noted 20.6, 3.1, and 1.8, respectively, to be the Positive Likelihood Ratio.
• Based on the results, the Negative Likelihood Ratio was 0.3, 0.3, and 0.5, respectively.
• In patients with cervical length shortening between 15-30 mm for the prediction of spontaneous preterm birth, positive predictive value for PAMG-1 and phIGFBP-1 tests was 60.9% (14/23) and 28.1% (16/57), respectively.
• They found the negative predictive value to be 97.1% (168/173) and 97.8% (136/139), respectively.
• In the 15-30 mm cohort, the prevalence of spontaneous preterm birth was 9.7% (19/196).
• The Positive Likelihood Ratio was noted to be 14.5 and 3.6, respectively.
• The Negative Likelihood Ratio was reported to be 0.3 and 0.2, respectively.