Value of determination of beta 2-microglobulin in toxic nephropathy and interstitial nephritis.

Beta 2-microglobulin (beta 2-m) is a low molecular weight protein of importance in the evaluation of the reabsorptive capacity of the proximal kidney tubule. This is based on the properties of beta 2-m: the daily production is constant and it leaves the body almost exclusively by glomerular filtration; 99.9% of the filtered amount is reabsorbed by the proximal tubule. The urinary excretion of beta 2-m is elevated (greater than 370 micrograms/day) in patients suffering from proximal tubular dysfunction with disturbance of tubular reabsorption. It is of great value as a marker of tubular involvement in toxic nephropathies, interstitial nephritis and the non-invasive method of choice to distinguish between renal and lower urinary tract infections.