Evaluation of maternal plasma creatine kinase activity as a marker of abnormal early pregnancy

We have tested the value of maternal plasma creatine kinase activity fordiagnosing ectopic pregnancies obtained after in-vitro fertilization andembryo transfer. Plasma creatine kinase was assayed in 57 patients: 20normal, 23 miscarriages and 14 ectopic pregnancies, for a total of 240samples. All values were in the lower part of the normal range except onlyone in a miscarrying patient. A statistically significant difference wasobserved for a cut-off value of 45 IU/l between normal and ectopicpregnancies. However, for this cut-off point, the measurement of plasmacreatine kinase activity had a sensitivity of 0.50 and a specificity of0.76 for the diagnosis of ectopic pregnancy. The positive predictive valuewas 0.69. Creatine kinase activity measurements are thus of no practicalvalue in this particular population, in which an early and specific markerof ectopic implantation would be of paramount interest. The association ofhuman chorionic gonadotrophin (HCG) determinations and ultrasound scanningof the pelvis still remain the best paraclinical support for an earlydiagnosis of ectopic implantation.