title: The relationship between pyuria and infection in patients with indwelling urinary catheters: a prospective study of 761 patients.
abstract: BACKGROUND
  Pyuria is universally considered as essential for identifying urinary tract infections in noncatheterized patients. The utility of pyuria in the catheterized patient, to identify catheter-associated urinary tract infection (CAUTI), has not been adequately defined.
  
  
  METHODS
  We prospectively studied 761 newly catheterized patients in a university hospital; 82 (10.8%) developed nosocomial CAUTI (> 10(3) colony-forming units per milliliter). While catheterized, each patient was seen daily, a quantitative urine culture was obtained, and the urine white blood cell concentration was measured quantitatively using a hemocytometer.
  
  
  RESULTS
  The mean urine leukocyte count in patients with CAUTI was significantly higher than in patients without infections (71 vs 4 per microliter; P= .006). Pyuria was most strongly associated with CAUTI caused by gram-negative bacilli (white blood cell count, 121 vs 4 per microliter; P = .03); infection with coagulase-negative staphylococci and enterococci (white blood cell count, 39 vs 4 per microliter; P = .25) or yeasts (white blood cell count, 25 vs 4 per microliter; P = .15) produced much less pyuria. Pyuria with a white blood cell count greater than 10 per microliter (>5 per high-power field in a conventional urinalysis) had a specificity of 90% for predicting CAUTI with greater than 10(5) colony-forming units per milliliter but a sensitivity of only 37%.
  
  
  CONCLUSIONS
  In patients with short-term indwelling urinary catheters, pyuria is less strongly correlated with CAUTI than in noncatheterized patients with urinary tract infection. The strongest association is with CAUTI caused by gram-negative bacilli; the association is far weaker for infections caused by gram-positive cocci or yeasts. Most patients with CAUTI are asymptomatic and do not have associated fever. Pyuria should not be used as the sole criterion to obtain a urine culture in a patient with a catheter.
authors.affiliation: Department of Medicine, University of Wisconsin Medical School, Madison, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Tambyah
authors.forename: D G
authors.initials: DG
authors.lastname: Maki
mesh_terms: D000328:Adult; D000368:Aged; D001437:Bacteriuria / Q000150:complications* / Q000175:diagnosis / Q000209:etiology* / Q000382:microbiology; D002408:Catheters, Indwelling / Q000009:adverse effects / Q000382:microbiology; D003428:Cross Infection / Q000175:diagnosis / Q000209:etiology* / Q000382:microbiology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011776:Pyuria / Q000175:diagnosis / Q000209:etiology* / Q000382:microbiology; D012680:Sensitivity and Specificity; D016482:Urinalysis; D014546:Urinary Catheterization / Q000009:adverse effects*