Serial beta-hCG measurements in the early detection of ectopic pregnancy

We investigated the sensitivity and specificity of serial serum hCG assays to diagnose early ectopic pregnancy in 50 asymptomatic women at risk. The initial two hCG values obtained at 2-5-day intervals were used to calculate doubling time and percentage increase. Twenty-five women had a viable intrauterine pregnancy, 14 an ectopic gestation, ten a spontaneous abortion, and one a molar pregnancy. A normal percentage increase and/or doubling time was observed in 64% of women who eventually proved to have an ectopic pregnancy. Ultimately, 85% of our patients demonstrated abnormal values when subsequent hCG pairs were analyzed. The sensitivity of these tests to diagnose asymptomatic ectopic pregnancy was 36%, with a specificity of 63-71%. We conclude that a normal rise in hCG production does not reliably differentiate an ectopic from an intrauterine pregnancy in the asymptomatic patient.