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[Gram stain and dipstick as diagnostic methods for urinary tract infection in febrile infants]
Benito Fernández J1, García Ribes A, Trebolazabala Quirante N
1Sección de Urgencias de Pediatría, Departamento de Pediatría. Hospital de Cruces. Bilbao. jbenito@hcru.osakidetza.net
Aim:
To compare urinary gram staining and dipstick for the detection of urinary tract infection (UTI)in febrile infants.
Methods:
Prospective study of 175 febrile infants aged 124 months. In all infants, a urine specimen was analyzed to detect UTI. The dipstick test was used to detect leukocytes and nitrites and samples were taken for gram staining and urine culture. Urine was obtained by urethral catheterization. Positive urine results were defined as 50.000 colony forming units per millimeter of urinary tract pathogen.
Results:
The mean age was 9.8 months (SD: 6.64). Urine culture was positive in 87 patients (49.5%). Diagnosis of UTI was confirmed in 91 patients (51.9%), of whom 74 were admitted for clinically suspected pyelonephritis (81.3%). Gram stain had the highest specificity (98.9%) and pyuria the highest sensitivity (90.8%). Better results were obtained using the combination of dipstick and Gram stain with a sensitivity of 93.1%, specificity of 98.4%, positive predictive value of 98.5% and negative predictive value of 92.5%.
Conclusions:
Urinary Gram stain appears to be more reliable than dipstick in detecting UTI in febrile infants but the results of both tests should be interpreted together.