Evaluation of serum creatine kinase in ectopic pregnancy with reference to tubal status and histopathology

Objective To study the value of creatine kinase in ectopic pregnancy with reference to tubal histopathology. Design Prospective controlled study. Setting Academic tertiary-care institution. Population Thirty-two women with ectopic pregnancy and 20 controls with intrauterine pregnancies. Methods Creatine kinase and beta-hCG levels were measured on admission. Ectopic pregnancies were removed at surgery and examined histologically. Main outcome measures Tubal localisation and integrity of ectopic pregnancies as judged at surgery and later histologically, and placental growth patterns in unruptured ectopic pregnancies classified as intraluminal, extraluminal or mixed as determined histologically. Results Creatine kinase levels were higher in isthmic than ampullary ectopic pregnancies (P = 0.011), and higher in ruptured than in unruptured cases (P = 0.003) and normal pregnancies (P < 0.0001). A creatine kinase value >120iu/L was 65% sensitive and 87% specific in discriminating ruptured from unruptured ectopic pregnancies. Creatine kinase levels were above this cutoff in two of five unruptured ampullary ectopic pregnancies with invasive trophoblastic growth, yet in none of nine cases with intraluminally confined placentation (P = 0.04). Creatine kinase was positively correlated with gestational age in ruptured (P = 0.007), but not in unruptured ectopic pregnancies or normal pregnancies. Conclusions Serum creatine kinase may help in discriminating ruptured from unruptured ectopic pregnancies, while it is not useful for the primary diagnosis of ectopic pregnancy. An increase in creatine kinase levels accompanying muscular damage in ectopic pregnancy probably antedates tubal rupture, and may be related to trophoblastic growth patterns.