Maternal serum creatine kinase as a biochemical marker of tubal pregnancy. 
To evaluate the role of serum creatine kinase as a possible marker for diagnosis of tubal pregnancy.  Five groups of patients were included in this prospective study: group A, 20 patients with tubal pregnancies; group B, 20 patients with missed abortions; group C, 20 patients with pelvic inflammatory disease; group D, 10 patients with acute appendicitis; group E (controls), 20 patients with normal pregnancies matched for age and gestation.  Total creatine kinase levels were measured in the serum of all five groups.  Creatine kinase levels were found to be > or =75 IU/l in all patients with tubal pregnancies, which was significantly higher than in the other four groups (P < 0.0001).  Our results indicate that maternal serum creatine kinase can be an important biochemical marker in suspected tubal pregnancy.