The need for a quantitative urine hCG assay

Abstract

Background The USA uniquely does not use quantitative urine human chorionic gonadotropin (hCG) tests despite being invaluable in pregnancy testing and in monitoring cancer patients. We look at current hCG tests and their detection of the degraded forms of hCG predominant in urine. We examine levels of urinary hCG, its usefulness in pregnancy testing, and advantages of urine testing in false positive hCG cases and cancer cases. Methods hCG assays were blindly evaluated at 10 laboratories running different methodologies. Daily urine samples from 164 women were collected through 5 menstrual cycles or until pregnancy was achieved. Urines were assayed for total hCG. We also examined the use of quantitative urine hCG in confirming false positive serum hCG results in 80 clinical cases. Results Only the Siemens Immulite test was shown to detect the degraded forms of hCG present in urine. This test equally recognized urine and serum hCG. We investigated background hCG in 9026 urines, the mean hCG level was 0.04 IU/L, and the 99th centile was 1.4 IU/L. In cycles where pregnancy was achieved, hCG could be detected in urine at 24.6 days of a 28.7 day menstrual cycle. At this time, the average hCG was 6.02 IU/L, setting a sensitivity level for quantitative urine hCG tests to detect pregnancy. Quantitative urinary hCG proved critical in detecting cancer in 3 of 80 cases complicated by false positive serum hCG. Conclusions The need for a quantitative urine hCG assay is undeniable and we invite manufacturers to produce a quantitative urine hCG test.