Excessively High Urinary Beta 2-Microglobulin Level: A Sign of Pathology or Laboratory Error ?

Measurement of urinary β2M (beta 2-microglobulin) is a sensitive and reliable assay for detecting tubular injury, renal toxicity, lymphomas, leukemia, or myeloma. Some chemical substrates may increase the level of β2M in-vivo. Elevated β2M level in urine is unusual because it rapidly degrades when pH is below 6. The level of β2M in the bladder can also be used as a marker to assess renal tubular maturation in neonates. β2M in the bladder could be a result of fetal megacystis, which is an abnormally enlarged bladder appearing after 10 weeks of gestation, when the fetus begins to produce urine. Identification of the pregnant women instead of the fetus is a common pre-analytical error with samples sent from the gynecology clinic to the laboratory. Here we present the case of a 24-year-old pregnant woman whose urine analysis results indicated excessively high β2M level in the urine. The present study could improve the understanding of urinary β2M analysis, laboratory errors, and the interpretation of test results.