title: Serum creatine kinase is an unreliable predictor of ectopic pregnancy.
abstract: OBJECTIVE
  To compare serum creatine kinase (CK) values in patients with ectopic pregnancy vs patients with threatened miscarriage or normal pregnancy.
  
  
  METHODS
  An observational case-control study was performed at an urban teaching hospital. Pregnant women with a quantitative beta-hCG obtained for suspicion of ectopic pregnancy were evaluated. Excluded were cases with recent trauma, i.m. injections, surgery, or history of heart, liver, or muscle disease. The serum beta-hCG and CK values were recorded and compared between groups with 1-way ANOVA and Tukey's multiple comparison procedure at the overall 0.05 level.
  
  
  RESULTS
  The 15 ectopic, 28 threatened miscarriage, and 21 normal pregnancy cases were of similar gestational ages (p = 0.2), ranging from 3 to 12 weeks. Although the CK values for ectopic pregnancy (88.8 +/- 33.6 IU/L) exceeded those for threatened miscarriage (65.9 +/- 59.0 IU/L) and normal pregnancy (56.0 +/- 38.1 U/L) (p = 0.02), there was significant overlap between groups. CK values were at or above a cutoff of 74 IU/L in 80% (95% confidence interval: 52-96%) of ectopic pregnancies, 25% (11-45%) of threatened miscarriages, and 14% (3-36%) of normal pregnancies.
  
  
  CONCLUSIONS
  Although the ectopic pregnancy population is characterized by a higher mean CK than are patients with threatened miscarriage or a normal pregnancy, a significant overlap in CK values makes use of this serum marker unreliable for detecting ectopic pregnancy.
authors.affiliation: St. Vincent Mercy Medical Center, Department of Surgery, Medical College of Ohio, Toledo 43608, USA. mcplewa@msn.com
authors.forename: M C
authors.initials: MC
authors.lastname: Plewa
authors.forename: D
authors.initials: D
authors.lastname: Ledrick
authors.forename: N F
authors.initials: NF
authors.lastname: Buderer
authors.forename: R W
authors.initials: RW
authors.lastname: King
mesh_terms: D000033:Abortion, Threatened / Q000097:blood; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D003402:Creatine Kinase / Q000097:blood*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000097:blood* / Q000175:diagnosis*; D012016:Reference Values
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D003402:Creatine Kinase