Urinary alpha 1-microglobulin detects uropathy. A prospective study in 483 urological patients

The aim of the study was to evaluate prospectively urinary alpha 1-microglobulin as a marker of proximal tubular damage following acute pyelonephritis and outflow disease of the upper urinary tract in a urological population with minimal exclusion criteria. We also measured the urinary gamma-glutamyltransferase activity, urinary albumin, urinary and serum creatinine, serum IgA and serum alpha 1-microglobulin.

We studied 483 urological patients (age: 1 to 92 years, 297 men, 186 women) excluding patients receiving nephrotoxic drugs, or suffering from type 1 diabetes or renal diseases. There were 141 patients with urinary tract infection but no fever, 36 patients with high fever of non-renal origin, 51 patients with acute pyelonephritis and 156 patients with outflow disease of the upper tract, and 99 patients were included in the reference population.

For acute pyelonephritis, vesico-ureteral reflux, and ureteral obstruction, urinary alpha 1-microglobulin had a sensitivity of 94%, 90% and 63% respectively and a specificity of 67%, 77% and 76%. The area under the curve of the receiver operator characteristic curve was significantly (p < 0.001) higher for urinary alpha 1-microglobulin than for albumin or gamma-glutamyltransferase activity. Unexpected positive results were found in acute prostatitis. The urinary alpha 1-microglobulin was the only parameter which differentiated between acute prostatitis and pyelonephritis (p < 0.001). Creatinine clearance or age had little and gender had no influence on the urinary excretion of alpha 1-microglobulin. Urine production rate significantly increases the urinary alpha 1-microglobulin/creatinine ratio.

Our results suggest that the urinary alpha 1-microglobulin/creatinine ratio is a diagnostically useful marker of tubular damage in acute pyelonephritis and vesico-ureteral reflux in the urological population. Following renal colic and chronic ureteral obstruction, a significant increase in urinary alpha 1-microglobulin excretion was observed.