Predictive value of a single serum pregnancy associated plasma protein-A or progesterone in the diagnosis of abnormal pregnancy

The value of a single measurement of serum levels of pregnancy associated plasma protein-A (PAPP-A) or progesterone (P4) in predicting abnormal gestations was assessed in 65 patients. P4 was greater than 20 ng/ml (mean +/- SEM 61.2 +/- 6.6 ng/ml, range 22.4-100.0 ng/ml) in all patients with normal intrauterine pregnancies (n = 21), and greater than 20 ng/ml (mean +/- SEM 8.5 +/- 3.9 ng/ml, range 0.1-68.8 ng/ml) in 16 out of 17 patients destined to abort spontaneously. Patients with ectopic gestations (n = 27) exhibited P4 values less than 20 ng/ml (mean +/- SEM 6.4 +/- 1.2 ng/ml, range 0.1-17.2 ng/ml). P4 levels in normal pregnancies were significantly higher (P = 0.001) than those of abnormal gestations. PAPP-A levels ranged from undetectable to 6448 mIU/ml in normal gestations. In 42 out of 44 abnormal pregnancies levels of PAPP-A were less than 100 mIU/ml, as were 7 out of 14 normal intrauterine pregnancies of less than 7 weeks gestational age. No ectopic demonstrated a value of PAPP-A greater than 50 mIU/ml and in 23 out of 27 ectopics, levels were undetectable. However, PAPP-A was less specific than P4 in correctly discriminating normal from abnormal gestations and exhibited lower positive and negative predictive values. It can be concluded therefore that a single PAPP-A measurement is of limited value in discerning normal from abnormal pregnancy prior to 8 weeks gestation. However, a single serum P4 is highly accurate and specific in detecting abnormal pregnancy, regardless of gestational age.