The utility of maternal creatine kinase in the evaluation of ectopic pregnancy

This investigation was designed to evaluate the utility of maternal creatine phosphokinase (CPK) in predicting the presence of an ectopic pregnancy (EP) in an emergency department (ED) setting. Twenty-one patients with the diagnosis of EP were randomly matched (1:1) with pregnant patients who subsequently ruled-out for EP. Serum CPK values at presentation were compared between the groups using two-tailed ANOVA, odds ratio, and frequency tables were generated using our a priori hypothesis that a serum CPK of >70 mlU/dL may be useful as a predictor of EP. The mean serum CPK was 118mlU/dL in the EP group and 64 mlU/dL in the non-EP group (P < .0031). Controlling for age, race, and gestational age, there was an association between elevated serum CPK and EP in our study population (with an odds ratio of 6.5). The categorical evaluation (with 95% confidence interval [CI]) of CPK (>70 mIU/dL) as a predictor of EP follows: sensitivity - 100% (80.8 to 100); specificity-- 61.9% (38.7 to 81); PV(+) - 72.4% (52.5 to 88.6); PV(-) - 100% (71.7 to 100). We therefore conclude that a CPK level >70 mIU/dL may serve as an important adjuvant diagnostic tool in ruling-out EP.