Serum levels of smooth muscle heavy-chain myosin in patients with ectopic pregnancy

Study objective: Previous studies have suggested that serum markers of smoo th muscle destruction have utility in predicting ectopic pregnancy. Our goa l was to determine whether a novel marker of muscle destruction, smooth mus cle heavy-chain myosin (SMHC), is elevated in the serum of patients with ec topic pregnancy. Methods: We conducted a prospective cohort study, with consecutive enrollme nt, of all women in the first trimester of pregnancy who presented to our u rban emergency department with complaints of lower abdominal pain with or w ithout vaginal bleeding. Patients were excluded if there was a history of r ecent surgery or major trauma. Means were compared using 2-tailed Student's t test with P values less than .05 set for significance. Data analysis inc luded calculation of receiver operating characteristic (ROC), 95% confidenc e intervals (Cls), and a regression model. Results: A total of 175 patients were enrolled; ectopic pregnancy was diagn osed in 29, and 146 had other diagnoses. Patients with ectopic pregnancy ha d a mean serum SMHC con centration of 2.53 ng/dL (95% CI 1.84 to 3.22), whe reas those in the non-ectopic pregnancy group had a mean concentration of 1 .41 ng/dL(95% CI 1.23 to 1.60; P<.0001). ROC analysis demonstrated an area under the curve of 0.72 (95% Cl 0.65 to 0.79). Regression analysis to exami ne confounders in each group analyzed the effects of race, maternal age, es timated gestational age, and serum levels of human chorionic gonadotropin b eta-subunit. Our analysis identified only a positive correlation between es timated gestational age and SMHC in the non-ectopic pregnancy group. Conclusion: There is a statistically significant elevation of serum SMHC le vels in tubal pregnancy, although our data suggest that the assay has limit ed clinical utility as a lone marker for ectopic pregnancy. Further investi gation is needed to determine whether the assay has a role as an adjunct in the evaluation of suspected ectopic pregnancy.