Neutrophil enzymes in urine for the detection of urethral infection in men.

OBJECTIVES--To determine if assaying the neutrophil enzymes, neutrophil elastase (NE) and myeloperoxidase (MPO) in the urine of men attending a genitourinary medicine clinic could identify those with Neisseria gonorrhoeae or Chlamydia trachomatis infections, and those with urethritis (with or without an identified infection with either organism), and to compare the new assays with the performance of the leucocyte esterase test (LET). METHOD--100 men had urethral specimens taken for Gram-stained urethral smear, culture for N gonorrhoeae, and for C trachomatis testing by enzyme immunoassay. First-voided urines were tested for leucocyte esterase by commercial dipstick (positives were defined as greater than "trace") and then frozen at -20 degrees C prior to being assayed for NE and MPO. RESULTS--Five patients had gonorrhoea, six had chlamydia and none had both. Evidence of urethritis (> 5 polymorphonuclear leucocytes in four x 1000 fields) was found in 29 men. The results of the urine assays showed MPO levels to be non-discriminatory; however NE levels were significantly elevated in patients with proven infection or urethritis or both. Using NE values from men with no infection or urethritis an upper limit for normal was defined. Utilising this, the sensitivity of the elastase assay was calculated and found to be superior to the sensitivity of LET for detecting proven infection (64% vs 36%) and urethritis (52% vs 31%). CONCLUSIONS--Further studies of neutrophil elastase in the pathogenesis, diagnosis and treatment of urethritis are indicated.