Urinary alanine aminopeptidase and beta 2-microglobulin as measurements of aminoglycoside-associated renal impairment.

The value of urinary alanine aminopeptidase (AAP) and urinary beta 2-microglobulin as predictors of aminoglycoside-associated nephrotoxicity was studied in 46 patients treated with gentamicin or tobramycin. In three patients serum creatinine increased by more than 50 mumol/l. Urinary AAP increased in virtually all patients. The degree of these increases could not be correlated to subsequent increases in serum creatinine. Increases in urinary beta 2-microglobulin were also seen in many patients who did not show subsequent increases in serum creatinine. Moreover, urinary beta 2-microglobulin was elevated before the onset of aminoglycoside treatment in many patients with septicaemia and malignant diseases, thus making an evaluation of antibiotic-induced changes impossible. These results indicate that neither urinary AAP nor urinary beta 2-microglobulin can be used to predict aminoglycoside-associated nephrotoxicity of clinical importance in individual patients.