Observations on the log human chorionic gonadotropin-time relationship in early pregnancy and its practical implications.
In this study, we examined whether the doubling time of human chorionic gonadotropin is different at different stages of early pregnancy and whether the use of multiple nomograms for doubling time of human chorionic gonadotropin rather than a single critical value can improve the diagnosis of ectopic pregnancy. Forty-four women with intrauterine pregnancies who had abdominal pain and/or vaginal bleeding but who did not abort their pregnancies and 44 women with surgically proved ectopic pregnancies were studied. No difference was found in the doubling time of human chorionic gonadotropin when women were classified according to recently published criteria (Pittaway DE, Reish RL, Wentz AC. Doubling times of human chorionic gonadotropin increase in early viable intrauterine pregnancies. Am J Obstet gynecol 1985;152:299-302), and estimates of the doubling time of human chorionic gonadotropin were not influenced by the initial human chorionic gonadotropin values or the sampling interval used. In the human chorionic gonadotropin range of practical interest, multiple nomograms identified 26 of 33 (79%) women with ectopic pregnancy who had rising levels of human chorionic gonadotropin, whereas our previously reported criteria identified 28 of 37 (76%) cases. The false positive rate for each method was 9.7%. Seventeen (19%) of 88 patients could not be allotted to the human chorionic gonadotropin categories for which nomograms of the doubling time of human chorionic gonadotropin have been derived. We conclude that our previous recommendations for determining the rate of increase of human chorionic gonadotropin in serum from paired samples do not require revision at this time.