Maternal creatine kinase is not a reliable diagnostic marker for ectopic pregnancy

Abstract

OBJECTIVE: To evaluate the efficacy and reliability of maternal serum creatine kinase (CK) as a diagnostic marker for ectopic pregnancy. STUDY DESIGN: A total of 168 patients were included in this prospective study. Patients were divided into three groups. Group A consisted of 68 women presenting with possible ectopic pregnancy. Group B consisted of 50 women with normal intrauterine pregnancies and group C consisted of 50 cases with missed abortions matched for gestational age. Patients having a diagnosis of recent major trauma, noro-muscular system disorder, thyroid disorder or heart disease were excluded. Blood samples were obtained for CK, beta-human chorionic gonadotropin (beta-hCG) and progesterone measurements on admission and a transvaginal sonogram was performed prior to surgical intervention. Data were compared between groups using receiver operating characteristic (ROC) curve and one-way ANOVA with Tukey's post test. RESULTS: While mean serum CK levels were higher (p<0.0001), serum beta-hCG and progesterone levels were found to be lower in ectopic pregnancies (p<0.0001 and p<0.0001; respectively) relative to missed abortions and normal pregnancies. Receiver operating characteristic (ROC) curve analysis revealed an area under the curve of 0.715 for CK, 0.914 for beta-hCG and 0.961 for progesterone. A CK value >45 IU/L was 60.3% sensitive and 77.8% specific, a beta-hCG value <4229 mIU/mL was 100% sensitive and 75% specific and a progesterone value <5.7 ng/mL was 100% sensitive and 79.4% specific in the diagnosis of ectopic pregnancy. CONCLUSİON: Although the mean value of serum CK is statistically significantly higher in ectopic pregnancy relative to controls, the positive predictive value and the sensitivity of CK is poor to allow CK to be a useful screening tool, comparing to beta-hCG and progesterone.