Limitations in qualitative point of care hCG tests for detecting early pregnancy

Abstract

BackgroundDetection of early pregnancy in the healthcare setting is important for proper patient management. Qualitative point-of-care (POC) human chorionic gonadotropin (hCG) testing is often used. There is a gap in the literature for evaluating patient samples with low (<300IU/l) hCG concentration using POC devices. MethodsSpecimens (urine, n=289; serum, n=269) with hCG concentrations between 2 and >5000IU/l were evaluated by hCG POC testing. Approximately half of these had an hCG concentration<300IU/l. All specimens were evaluated using the OSOM and QuickVue+ POC hCG devices. Pregnancy status was evaluated by patient chart review. ResultsThe OSOM and QuickVue+ devices were able to detect hCG in 53% (OSOM) and 78% (QuickVue+) of urine samples with an hCG concentration range between 20 and 300IU/l. Serum samples with an hCG concentration range between 10 and 300IU/l gave positive results in 79 and 91% of samples tested using the OSOM and QuickVue+, respectively. False negative results could not be attributed to the high-dose hook effect, the hCG variant effect, or the interpreters' evaluation. The mean gestational age for specimens corresponding to the false negative results was 4weeks. ConclusionsThe sensitivity of 2 commonly used hCG POC devices is insufficient for detecting very early pregnancy.