Evaluation of the beta-Neocept test for early pregnancy

Abstract

We tested the validity of the beta-Neocept test for early pregnancy against that of the plasma human chorionic gonadotropin beta-subunit radioimmunoassay (beta-HCG RIA). The beta-Neocept test had a sensitivity of 88%, a specificity of 93%, a positive predictive value of 95%, a negative predictive value of 84% and an accuracy of 90%. In view of these performance characteristics, its low cost and its ease of use, the beta-Neocept test could be used as the initial pregnancy test when there is a high probability of pregnancy, as there was in this study population, which consisted of 111 women attending endocrine infertility clinics. The more expensive beta-HCG RIA could be reserved for special indications and for patients in whom the results of the urinary hemagglutination inhibition tests are inconsistent with the clinical signs and symptoms.

PIP: Paired urine and blood samples from 111 women attending endocrine infertility clinics in Vancouver, Canada, were used to compare the validity of the beta-Neocept test for early pregnancy against that of the plasma human chorionic gonadotropin beta-subunit radioimmunoassay (beta-HCG-RIA). None of the urine specimens contained glucose, 1 specimen contained 1 + protein measured by dipstick, and 1 contained a large amount of blood. 67 patients were pregnant and 44 were not pregnant. Beta-Neocept test results were positive for 59 pregnant patients, negative for 8 pregnant patients, positive for 3 nonpregnant patients, and negative for 41 nonpregnant patients. There were 62 positive and 49 negative tests. Results with the Beta-Neocept test became positive as early as the 28th day after the onset of the last menstrual period and negative results occurred with plasma beta-HCG levels ranging between 5 and 157 IU/1. The sensitivity of the Beta-Neocept test was 88%, the specificity 93%, the positive predictive value 95%, the negative predictive value 84%, and the overall accuracy 90%. The 8 false-negative results all occurred at low plasma beta-HCG levels. The false-negatives occurred in 1 patient on no medication, 1 taking clomiphene citrate and prednisone, 1 taking gonadotropin releasing hormone (GRH), 1 taking human menopausal gonadotropin and human chorionic gonadotropin, 1 taking GRH and bromocriptine mesylate, 1 taking clomiphene citrate alone, and 2 taking clomiphene citrate and progesterone vaginal inserts. The 3 false-positive results occurred in 2 patients using progesterone vaginal inserts for luteal-phase support and 1 who was taking clomiphene citrate. The results indicate that the Beta-Neocept test is sensitive and specific, and would be an appropriate initial test for patients with a high probability of pregnancy. The beta-HCG-RIA could be reserved for patients in whom the results of the less expensive and less difficult Beta-Neocept were inconsistent with clinical signs and symptoms.