Two-step diagnostic rule aids UTI detection, antibiotic treatment in children
A diagnostic rule based on symptoms and signs performs better than clinical diagnosis in identifying young children who should undergo noninvasive urine testing for urinary tract infection (UTI) and guiding potential antibiotic treatment, as presented in the results of DUTY* Prospective Diagnostic Cohort Study.
The rule can be broken down into two steps: (1) use symptoms and signs to select children for urine sampling, and (2) utilise the dipstick results to guide empiric antibiotic treatment.
“Pain or crying while passing urine, smelly urine, previous UTI, absence of severe cough, severe illness, abdominal tenderness, and absence of ear abnormalities can be used for deciding which children for whom a urine sample… and dipstick results would improve specificity for antibiotic treatment,” said the investigators, led by Dr. Alastair Hay from the University of Bristol and Dr. Christopher Butler from the University of Oxford.
“Three or more of these symptoms suggest it is worthwhile going to the effort of getting a urine sample. Surprisingly, fever was not a useful indicator for identifying children with UTI in primary care,” Hay said.
Hay, along with Butler and the others, examined urine samples from 3,036 acutely unwell children aged <5 years. Of these, culture results were obtained in 2,740 (90 percent), accounting for 60 (2.2 percent) who showed laboratory evidence of UTI. Antimicrobial substances were present in 128 (4.5 percent) urine samples and in 4 (6.7 percent) UTI-positive samples. [Ann Fam Med 2016;14:325-336]
Pre-dipstick clinical evaluation yielded a UTI diagnosis in 168 (6.1 percent) children, and 28 (16.7 percent) of them were UTI positive. The resulting sensitivity and specificity were 46.6 and 94.7 percent, respectively, with an area under receiver operating characteristic curve (AUROC) of 0.77 (95 percent CI, 0.71 to 0.83).
All previously mentioned symptoms were associated with UTI. In analyses using coefficient-based (graded severity) and points-based (dichotomised) models, AUROCs were 0.87 (0.89; 0.84 to 0.94) and 0.86, respectively. The addition of dipstick leukocytes nitrites, and blood—all of which having a strong association with UTI—increased the AUROCs to 0.9 (0.93; 0.89 to 0.96) and 0.9, respectively. AUROCs were corrected for overoptimism.
“If all children had a urine sample and dipstick test, the dipstick test results could maintain sensitivity at 80 percent while improving specificity from 88.3 to 93.8 percent and reducing the percentage of children treated with antibiotics from 13.2 to 7.8 percent, assuming immediate antibiotic use,” the investigators noted.
Serious adverse events were minimal, with hospitalisation occurring in 1.1 percent of the 7,163 originally recruited children. Of these, 3 cases were associated with dipstick testing.
The findings highlight the superiority of the 2-step UTI diagnostic rule to clinical diagnosis. Further, “dipstick testing was diagnostically superior to symptoms and signs alone… and was not diagnostically useful in children with the lowest UTI probability, for whom step 1 would not result in urine collection,” the investigators said.
“Precisely how these results are used is likely to depend on clinician preference. Some clinicians may wish to use these as risk factors to feed into clinical judgment. Others may prefer to use a checklist approach and use the points-based clinical rules… which focus attention on predictive factors rather than those (such as fever) with poor diagnostic utility,” they added.
“Clinicians concerned about overdiagnosis and treatment could select a higher specificity threshold, whereas higher sensitivity thresholds would reduce underdiagnosis. When the rule is used, it should supplement, not replace, clinical judgment.”
* Diagnosis of Urinary Tract Infection in Young children