Evaluation of leukemia inhibitory factor as a marker of ectopic pregnancy

Objective: Our purpose was to determine the utility of measuring serum leukemia inhibitory factor, a cytokine expressed in the process of pregnancy implantation, for the diagnosis of ectopic pregnancy. Study Design: Serum samples from 40 patients with positive serum quantitative β-human chorionic gonadotropin levels were used for leukemia inhibitory factor determination. The serum leukemia inhibitory factor concentration was determined by enzyme-linked immunosorbent assay in the following 4 groups: (1) normal intrauterine pregnancies, (2) threatened abortions, (3) spontaneous abortions, and (4) ectopic pregnancies. Results: All patients had detectable concentrations of leukemia inhibitory factor in serum, ranging from 2.44 to 8.25 pg/mL. Mean leukemia inhibitory factor concentrations for ectopic pregnancy were significantly lower (P< .05) than those of both the spontaneous abortion and threatened abortion groups by 1-way analysis of variance. When a cutoff point of serum leukemia inhibitory factor <6.2 pg/mL is assigned as diagnostic of ectopic pregnancy, leukemia inhibitory factor in patients with ectopic pregnancies versus all other groups predicted ectopic pregnancy with a sensitivity of 73%, specificity of 72%, positive predictive value of 50%, and negative predictive value of 88%. Conclusion: Serum leukemia inhibitory factor concentration is lowest in patients with ectopic pregnancy. A cutoff point of 6.2 pg/mL maximizes the sensitivity and specificity of the test; however, it is not sufficiently discriminatory to be used clinically for the diagnosis of ectopic pregnancy. (Am J Obstet Gynecol 2001;184:1074-6.)