Relative operating characteristic analysis in reproductive medicine: comparison of progesterone and human chorionic gonadotropin doubling time as predictors of early gestational normalcy.

OBJECTIVE: To directly compare the ability of serum P and hCG doubling time to predict early gestational complications.
DESIGN: We analyzed differences in P concentrations and hCG doubling times between spontaneously conceived normal and abnormal pregnancies (abortions and tubal pregnancies) during the first 49 days of pregnancy. Multiple 2 x 2 contingency tables were constructed that compared pregnancy outcome within discriminatory serum P concentrations or hCG doubling time. From these tables relative operating characteristic curves were generated for P concentration and hCG doubling times. The area under the curves were estimated and compared by the critical z score.
RESULTS: Calculation of the areas under the curve for hCG doubling time and P concentration yielded values of 0.799 +/- 0.056 and 0.780 +/- 0.051 (mean +/- SEM), respectively. Critical z testing did not reveal a significant difference between the two curves.
CONCLUSION: Serum P and hCG doubling times equally predict early gestational normalcy. Thus, a single serum P may be just as valuable in estimating risks of early pregnancy complications as repeated hCG measurements.