Reporting specific gravity urine with pregnancy test.Reporting specific gravity urine with pregnancy test Q Our current practice has been to report the urine-specific gravity with every urine pregnancy test (hCG test). This was to let the physician know this result may be falsely negative when urine is diluted. In our last Joint Commission inspection, the inspector noted we did not need to do this and that no one else does this. Is reporting the specific gravity unnecessary? Is this a known limitation by the physician? Should we just comment this limitation with the results? What do other labs do? Or do we not address the specific gravity at all? A In the past, it was usual to request the first morning urine specimen and to test and ensure that specific gravity of the urine was at least 1.015 when performing a urine pregnancy test. This was necessary because of the relative insensitivity of the commonly used pregnancy tests that required levels of 1,000 IU hCG or more to show a positive result. Current EIA (Electronic Industries Alliance, Arlington, VA, www.eia.org) A membership organization founded in 1924 as the Radio Manufacturing Association. It sets standards for consumer products and electronic components. (enzyme immunoassay Immunoassay An assay that quantifies antigen or antibody by immunochemical means. The antigen can be a relatively simple substance such as a drug, or a complex one such as a protein or a virus. ) or ELISA ELISA (e-li´sah) Enzyme-Linked Immuno-Sorbent Assay; any enzyme immunoassay using an enzyme-labeled immunoreactant and an immunosorbent. ELISA n. (enzyme linked immunosorbent immunosorbent /im·mu·no·sor·bent/ (-sor´bent) an insoluble support for antigen or antibody used to absorb homologous antibodies or antigens, respectively, from a mixture; the antibodies or antigens so removed may then be eluted in pure assay) tests are significantly more sensitive, commonly with sensitivities of 25 IU hCG or less; however, although any random urine specimen is acceptable, a first morning-voided urine is preferred. In cases of very early pregnancy, it is possible to obtain a false-negative result if the level of hCG is below the detectable level due to urine dilution. This is extremely rare; however, especially in very early pregnancy, a serum specimen is preferred to a urine specimen. Most tests that are commercially available can be performed with urine or serum. --Karen M. Ringsrud, MT (ASCP ASCP American Society of Clinical Pathologists. ) Assistant Professor (Ret.) Department of Laboratory Medicine and Pathology University of Minnesota Medical School The University of Minnesota Medical School is the medical school of the University of Minnesota. It is a combination of two campuses situated in Minneapolis and Duluth, Minnesota. Minneapolis, MN Edited by Daniel M. Baer, MD |
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