Urine qualitative hCG POCT has several limitations that could lead to false negative results. These include: a) lower sensitivity during the first 4 weeks of gestation compared to serum hCG, b) unreliable detection of an hCG degradation product that is the major form of hCG excreted in urine during the late first and entire second trimester, c) susceptibility to ‘high-dose hook effects’ that can occur with very high levels of hCG, d) reduced urine excretion of hCG in ectopic pregnancy, toxemia of pregnancy and threatened miscarriage, and e) hCG being undetectable in dilute urine. Given the limitations of urine hCG POCT, quantitative blood hCG should be the test of choice unless urine hCG POCT significantly improves clinical management. Performing urine POCT in settings where blood hCG is accessible in a timely manner can lead to unnecessary duplication and negatively impact patient care.
Sources:
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Johnson S, et al. Significance of pregnancy test false negative results due to elevated levels of β-core fragment hCG. J Immunoassay Immunochem. 2017;38(4):449-455. PMID: 28521601.
Kleinschmidt S, et al. False negative point-of-care urine pregnancy tests in an urban academic emergency department: a retrospective cohort study. J Am Coll Emerg Physicians Open. 2021;2(3):e12427. PMID: 33969349.
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