Can a Simple Urinalysis Predict the Causative Agent and the Antibiotic Sensitivities?

Abstract

Objectives The objective of this study was (1) to determine the reliability of urinalysis (UA) for predicting urinary tract infection (UTI) in febrile children, (2) to determine whether UA findings can predict Escherichia coli versus non–E. coli urinary tract infection, and (3) to determine if empiric antibiotics should be selected based on E. coli versus non–E. coli infection predictions. Methods This was a retrospective chart review of children from 2 months to 2 years of age who presented to the emergency department with fever (rectal temperature >100.4°F) and had a positive urine culture. This study was conducted between January 2004 and December 2007. Negative UA was defined as urine white blood cell count less than 5 per high-power field, negative leukocyte esterase, and negative nitrites. Urine cultures were classified into E. coli and non–E. coli groups. These groups were compared for sex, race, and UA findings. Multivariate forward logistic regression, using the Wald test, was performed to calculate the likelihood ratio (LR) of each variable (eg, sex, race, UA parameters) in predicting UTI. In addition, antibiotic sensitivities between both groups were compared. Results Of 749 medical records reviewed, 608 were included; negative UA(−) was present in 183 cases, and positive UA(+) was observed in 425 cases. Furthermore, 424 cases were caused by E. coli, and 184 were due to non–E. coli organisms. Among 425 UA(+) cases, E. coli was identified in 349 (82.1%), whereas non–E. coli organisms were present in 76 (17.9%); in contrast, in 183 UA(−) cases, 108 (59%) were due to non–E. coli organisms versus 75 (41%), which were caused by E. coli. Urinalysis results were shown to be associated with organism group (P < 0.001). Positive leukocytes esterase had an LR of 2.5 (95% confidence interval [CI], 1.5–4.2), positive nitrites had an LR of 2.8 (95% CI, 1.4–5.5), and urine white blood cell count had an LR of 1.8 (95% CI, 1.3–2.4) in predicting E. coli versus non–E. coli infections. Antibiotic sensitivity compared between UA groups demonstrated equivalent superiority of cefazolin (94.7% sensitive in UA(+) vs 84.0% in UA(−) group; P < 0.0001), cefuroxime (98.2% vs 91.7%; P < 0.001), and nitrofurantoin (96.1% vs 82.2%; P < 0.0001) in the UA(+) group. In contrast, the UA(−) group showed significant sensitivity to trimethoprim-sulfamethoxazole (82.2% vs 71.3% in UA(+); P = 0.008). Conclusions Urinalysis is not an accurate predictor of UTI. A positive urine culture in the presence of negative UA most likely grew non–E. coli organisms, whereas most UA(+) results were associated with E. coli. This study also highlighted local patterns of antibiotic resistance between E. coli and non–E. coli groups. Negative UA results in the presence of strong suspicion of a UTI suggest a non–E. coli organism, which may be best treated with trimethoprim-sulfamethoxazole. Conversely, UA(+) results suggest E. coli, which calls for treatment with cefazolin or cefuroxime.

Urinary Predictors of Bacteremia in Febrile Infants with Urinary Tract Infection

“…Although E.coli has also been associated with increased likelihood of leucocyte esterase and nitrite on urine dipstick [25], interestingly these urinary components were not significant predictors of bacteremia in our population. The relatively short incubation period of urine in the bladder of infants ≤ 24 months may explain why nitrite is not a sensitive predictor of UTI or bacteremia, but the non-significance of leucocyte esterase at predicting bacteremia remains unclear.…”

Diagnostic accuracy of urinary biomarkers in infants younger than 3 months with urinary tract infection

“… 22) Urinalysis (positive was defined as >5 WBC/HPF, positive leukocyte esterase, or positive nitrite) was positive in only 69% of samples with positive urine cultures in a retrospective review of children aged 2 months through 2 years presenting with fever. 23) Therefore, it is necessary to find an alternative reliable marker for the early diagnosis of UTI in febrile infants.…”

Approach to Neonates and Young Infants with Fever without a Source Who Are at Risk for Severe Bacterial Infection

“…However, whether dipstick urinalysis can be an accurate predictor of UTI is debated. In a retrospective study [82] of children from 2 months to 2 years old who presented to the emergency department with fever and a positive urine culture, only 69.9% of the patients with culture-proven UTIs had a positive urinalysis. Positive leucocyte esterase and nitrite were detected in 63.5% and 20.9% of the cases, respectively, suggesting that dipstick analysis adds little to the microscopic evaluation of pyuria independent of the suggested urine WBC thresholds [4–6].…”