Association Between Uropathogen and Pyuria. (Emrath)

Shaikh N, Shope TR, Hoberman A, Vigliotti A, Kurs-Lasky M, Martin JM. Association Between Uropathogen and Pyuria. Pediatrics. 2016 Jul;138(1). pii: e20160087.

OBJECTIVE: We sought to determine factors associated with the absence of pyuria in symptomatic children whose urine culture was positive for a known uropathogen.

METHODS: We obtained data on children evaluated at the Children’s Hospital of Pittsburgh emergency department between 2007 and 2013 with symptoms of urinary tract infection (UTI) who had paired urinalysis and urine cultures. We excluded children with an unknown or bag urine collection method, major genitourinary anomalies, immunocompromising conditions, or with multiple organisms on culture. We chose a single, randomly-selected urine specimen per child and limited the analysis to those with positive cultures.

RESULTS: There were 46 158 visits during the study period; 1181 children diagnosed with UTI met all inclusion criteria and had a microscopic urinalysis for pyuria. Pyuria (≥5 white blood cells per high-powered field or ≥10 white blood cells per cubic millimeter) was present in 1031 (87%) children and absent in 150 (13%). Children with Enterococcus species, Klebsiella species, and Pseudomonas aeruginosa were significantly less likely to exhibit pyuria than children with Escherichia coli (odds ratio of 0.14, 0.34, and 0.19, respectively). Children with these organisms were also less likely to have a positive leukocyte esterase on dipstick urinalysis. Results were similar when we restricted the analysis to children whose urine samples were collected by bladder catheterization.

CONCLUSIONS: We found that certain uropathogens are less likely to be associated with pyuria in symptomatic children. Identification of biomarkers more accurate than pyuria or leukocyte esterase may help reduce over- and undertreatment of UTIs.

Use of time from fever onset improves the diagnostic accuracy of C-reactive protein in identifying bacterial infections. (Kamat)

Segal I, Ehrlichman M, Urbach J, Bar-Meir M. Use of time from fever onset
improves the diagnostic accuracy of C-reactive protein in identifying bacterial
infections. Arch Dis Child. 2014 May 15.

OBJECTIVE: To determine whether the input of time from fever onset will change the accuracy of C-reactive protein (CRP) in diagnosing bacterial infections in febrile children.

STUDY DESIGN: We performed a prospective observational study on febrile children presenting to the emergency department. The diagnostic performance of CRP at different time points from fever onset was compared using a receiver operating characteristic (ROC) curve.

RESULTS: Among 373 patients included, 103 (28%) had bacterial infection. The optimal cut-off for CRP suggesting bacterial infection changed with time from fever onset: 6 mg/dL for >12-24 h of fever; 10.7 and 12.6 mg/dL at >24-48 and >48 h of fever, respectively. The input of time from fever onset improved the area under the ROC curve from 0.83 (95% CI 0.78 to 0.88) for CRP overall to 0.87 (95% CI 0.77 to 0.96) and 0.90 (95% CI 0.84 to 0.97) at >24-48 and >48 h of fever, respectively. Duration of fever mostly affected the ability of CRP to correctly rule out bacterial infections. CRP level of 2 mg/dL obtained at ≤24 h of fever corresponds with a post-test probability for bacterial infection of 10%, whereas the same value obtained >24 h of fever reduces the risk to 2%.

CONCLUSIONS: Clinicians should apply different CRP cut-off values depending on whether they are trying to rule in or rule out bacterial infection, but also depending on fever duration at the time of CRP testing.

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