Serum creatine kinase is an unreliable predictor of ectopic pregnancy.
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.
Plewa
M C
MC
St. Vincent Mercy Medical Center, Department of Surgery, Medical College of Ohio, Toledo 43608, USA. mcplewa@msn.com
Ledrick
D
D
Buderer
N F
NF
King
R W
RW
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
D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D003402:Creatine Kinase