Urinary plasma protein patterns in acute prostatitis

We evaluated the diagnostic utility of urinary alpha1-microglobulin, alpha2-macroglobulin and albumin in the diagnosis of acute prostatitis. We studied 133 men (43 +/- 17 years) with, and a reference population (n=36, 41 +/- 16 years) without, urinary tract infection. Prostatectomy samples were used to study the potential interference between prostatic proteins and protein analysis. Urinary alpha2-macroglobulin/albumin ratio was significantly lower in prostatitis compared to the reference population, cystitis or acute pyelonephritis (p < 0.0001). Low alpha2-macroglobulin concentrations in prostatitis are due to inhibition (p = 0.0001) of the immune reaction between alpha2-macroglobulin in presence of polyclonal rabbit antibodies (used for immunonephelometry) by soluble prostatic proteins (+/- 60 kDa) which appear in urine in acute prostatitis. The urinary alpha1-microglobulin/creatinine ratio diagnoses acute pyelonephritis (sensitivity 100% and specificity 87%) and the urinary alpha2-macroglobulin/albumin ratio diagnoses acute prostatitis (sensitivity 100% and specificity of 90%). Stepwise multinomial logistic regression analysis reveals that urinary alpha1-microglobulin, alpha2-macroglobulin, albumin and creatinine provide optimal differentiation between acute pyelonephritis and acute prostatitis (pseudo R2=0.83; Loglikelihood -30.55, p < 0.000001). In conclusion, the combination of hematuria and absence of urinary alpha-2-macroglobulin is diagnostic for acute prostatitis. Even without hematuria, alpha2-macroglobulin remains lower compared to patients without prostatitis.