Reference values for circulating pregnancy-associated microRNAs in maternal plasma and their clinical usefulness in uncomplicated pregnancy and hypertensive disorder of pregnancy

Aim: The aim of this study was to establish the reference values for circulating pregnancy-associated placental microRNAs in maternal plasma and clarify their clinical significance in patients with hypertensive disorder of pregnancy (HDP). Methods: Blood samples were collected from 145 women with uncomplicated pregnancies (24, 26, 31 and 32 women at 12, 23, 30 and 36 weeks of gestation, respectively, and 32 women 1 day after delivery). Plasma concentrations of pregnancy-associated placental microRNAs (miR-515-3p, miR-517a, miR-517c and miR-518b) were measured by quantitative real-time reverse-transcription polymerase chain reaction. Reference values for each microRNA were determined by the line of best fit and 95% prediction interval and are expressed as logarithmic transformation. To clarify the clinical significance of these reference values, we measured the plasma concentrations of pregnancy-associated microRNAs in a different population comprising 33 pregnant women with HDP and 44 women with uncomplicated pregnancies. Results: Reference values for circulating pregnancy-associated placental microRNAs on chromosome 19 miRNA clusters showed an increasing tendency as pregnancy progressed and decreased significantly 1 day after delivery (P < 0.05). The sensitivity and specificity of each reference value were 57.6% and 93.2% for miR-515-3p, 63.6% and 75.0% for miR-517a, 75.8% and 79.5% for miR-517c and 63.6% and 75.0% for miR-518b, respectively. The positive and negative predictive values of each reference value were 86.4% and 74.5% for miR-515-3p, 65.6% and 73.3% for miR-517a, 73.5% and 81.4% for miR-517c and 65.6% and 73.3% for miR-518b, respectively. Conclusion: Establishing the reference values for circulating pregnancy-associated placental microRNAs in maternal plasma could be useful for the evaluation of HDP.