|
Richard Bachur , MD; Marvin B. Harper , MD
Bachground:
Urinary tract infections (Utls) are a common source of
bacterial infection among younge febrile children. Clinical variables
affecting the sensitivity of the urinalysis (UA) as a screen for UTI
have not been previously investigated. The limited sensitivity of the
UA for detecting a UTI requires that a urine culture be obtained in
some children regardless of the UA result; however, a proper urine
culture requires an invasive procedure, so the criteria for its use
should be optimized.
Objectives:
To determine how the sensitivity of the standard UA as a screening
test for UTI varies with age, and to determine the clinical situation
that necessitates the collection of a urine culture regardless of the
UA result.
Methods:
Retrospective medical record review of patients younger than 2 years
with fever (>38C) seen in the emergency department during a period of
65 months. All urine cultures were reviewed for the collection method
, isolates , and colony counts. A UA result was considered positive if
the presence of l of the following was detected: leukocyte esterase ,
nitrite , or pyuria (>5 white blood cells per high power field ).
Patients who had a paired UA and urine culture were used to calculate
the sensitivity , specificity , and likelihood ratios of the UA. The
prevalence of UTIs was also subcategorized by age, race , sex , and
fever.
Results:
Medical records of 37450 febrile children younger than 2 years were
reviewed . Forty – four percent were girls . Median age and
temperature were 10.6 month and 38.8C .A total of 11089 patients (30%)
had urine cultures obtained. The sensitivity of the UA was 82% (95%
confidence interval [ CI], 79%-84%) and did not vary by age subgroups
. The specificity of UA was 92% (95% CI , 91%-92%) . The likelihood
ratios for a positive UA and negative UA were 10.6 (95%CI , 10.0-11.2)
and 0.19(95%CI , 0.18-0.20) , respectively , Prevalence of UTI was
2.1% overall (2.9% for girls and 1.5% for boys , respectively).Among
girls, the prevalence of UTI was 5.0% in white patients , 2.1% in
Hispanic patients , and 1.0% in black patients . Among boys , the
prevalence was 2.2% in Hispanic patients , 1.4% in white patients ,
and 0.8% in black patients . Higher prevalence was also seen among
patients with a temperature at or above 39C compared with those whose
tempearature was between 38.0C and 38.9C .The greatest prevalence of
UTI (13%) was found among white girls younger than 6 months with a
temperature at or greater than 39C. The posttest probability of a UTI
in the presence of a negative UA can be calculated using the negative
likelihood ratio and the patient-specific preva-lence of UTI . When
the prevalence of UTI is 2%, l UA among 250 will produce a
false-negative test result. |
