Reference interval of pregnancy-associated plasma protein-A in healthy men and non-pregnant women

ObjectiveThe serum pregnancy-associated plasma protein-A (PAPP-A) concentration is a predictor of ischemic cardiac events and renal impairment. However, the reference interval of PAPP-A has not been determined. This study determined the reference interval of PAPP-A in men and non-pregnant women.MethodsThe study enrolled 126 apparently healthy individuals (52 males and 74 females). The mean age of the men and women was 34.7 (range 20–66) years and 34.6 (range 18–65) years, respectively. Serum PAPP-A concentrations were determined using an ultrasensitive enzyme-linked immunoassay kit. Reference intervals were calculated using the bootstrap method.ResultsThe results for three subjects were outliers, so the reference interval of PAPP-A was calculated using the data for 123 subjects. PAPP-A was undetectable in 26 subjects. The reference interval of PAPP-A for men and women (with the 90% confidence interval) was <22.9 ng/mL (19.7–23.3) and <33.6 ng/mL (25.2–36.7), respectively. In male subjects, serum PAPP-A levels of smokers [3.10 (UD, 7.30) ng/mL] were significantly lower than that of non-smokers [11.00 (UD, 24.4) ng/mL] (p < 0.001) and there was a positive correlation between serum PAPP-A levels and subjects’ age (r = 0.439; p < 0.001).ConclusionsThe reference interval of PAPP-A differed for men and non-pregnant women. In clinical practice, <22.9 ng/mL for men and <33.6 ng/mL for non-pregnant women may be used as reference intervals for PAPP-A.