Significance of pregnancy test false negative results due to elevated levels of ß-core fragment hCG.

ABSTRACT

Very high levels of ß-core fragment human chorionic gonadotrophin (ßcf-hCG) are reported to potentially cause false negative results in point-of-care (POC)/over-the-counter (OTC) pregnancy tests. To investigate this further, women's daily early morning urine samples, collected prior to conception and during pregnancy, were analysed for intact, free ß-, and ßcf-hCG. The proportion of ßcf-hCG was found to be related to that of hCG produced and in circulation. Therefore, best practice for accuracy testing of POC/OTC pregnancy tests would be to test devices against clinical samples containing high levels of ßcf-hCG as well as standards spiked with biologically relevant ratios.