Journal of Pharmacy and Pharmacology 6 (2018) 101-105 doi: 10.17265/2328-2150/2018.01.011 Excessively High Urinary Beta 2-Microglobulin Level: A Sign of Pathology or Laboratory Error? Gulsum Feyza Altas¹, Pinar Akan¹ and Erkan Cagliyan² 1. Department of Medical Biochemistry, Faculty of Medicine, Dokuz Eylul University, Izmir 35000, Turkey 2. Department of Obstetrics and Gynecology, Faculty of Medicine, Dokuz Eylul University, Izmir 35000, Turkey Abstract: 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. Key words: Pre-analytical error, urinary β2M, fetal megacystis. 1. Introduction β2M (beta 2-microglobulin) is a small molecular weight protein found on the cell surface. It is present in most body fluids (blood, urine, cerebrospinal fluid) and its level rises with conditions that increase cell production and/or destruction or that activates the immune system [1]. Increased serum levels may indicate lymphomas, leukemia, or myeloma; glomerular renal disease; renal transplant rejection; viral infections, especially HIV and cytomegalovirus; or chronic inflammatory processes. Although the small size of β2M allows it to be filtered through the glomerular membrane, typically less than 1% of the filtered β2M is excreted in the urine [2]. The majority of β2M in the filtrate is reabsorbed and catabolized by renal proximal tubular cells [3]. Therefore, β2M serves as a useful biomarker to evaluate both glomerular and tubular function [4]. Measurements of proteinuria and enzyme-uria are Corresponding author: Gulsum Feyza Altas, M.D., research assistant, research fields: clinical biochemistry and laboratory diagnostics. simple, convenient and non-invasive diagnosis methods used for the early detection of renal damage [5, 6]. Measurement of urinary β2M is one of the most sensitive and reliable assay for detecting tubular injury [7]. Increased levels in the urine indicate renal tubule disease; drug-induced renal toxicity; heavy metal-induced renal disease; lymphomas, leukemia, or myeloma; or AIDS. Toxic elements such as cadmium and mercury, which cause tubular damage, significantly increase the amount of β2M in the urine. In occupational medicine, the determination of β2M in urine is regarded as the most sensitive test for early detection of tubular damage from excessive exposure to cadmium [8]. Drugs that can cause tubular dysfunction through toxicity, primarily aminoglycosides and lithium, cause an increase in the amount of β2M that is in eliminated in the urine. The nephrotoxicity of water-soluble urographic contrast material is also well recognized. Fulvio Stacul et al. demonstrated that contrast material causes significant increase in the urinary excretion of β2M. β2M can be used as a marker to assess renal tubular maturation in neonates. Either 24-hour urine or random D DAVID PUBLISHING