Pregnancy tests: evaluation of current status

During the past 2 decades, laboratorians have observed many changes in pregnancy tests, which are generally defined as procedures designed to detect elevated levels of hCG in urine and/or serum. The original tests were animal assays in which biologic changes were observed following the injection of urine. The currently most widely utilized tests are slide and tube tests, including some of with beta-subunit specificity, in which urine hCG is detected by immunologic antigen-antibody reactions. Finally, in some settings there has been increased testing for hCG by radioreceptor assays based on the binding of hCG to plasma membrane receptor sites and qualitative radioimmunoassay utilizing classic competitive binding techniques. This review compares the relative advantages and disadvantages of these procedures in regard to diagnostic effectiveness, sensitivity, specificity, cost variables, and technical requirements.