Developing clinical rules and a urinary dipstick rule to predict urinary tract infection in primary care settings
Abstract number: p985
Little P., Turner S., Rumsby K., Warner G., Moore M., Smith H., Hawkes C., Mullee M.
Suspected UTI is one of the commonest acute infections. Systematic reviews have documented no adequately powered studies in primary care to assess independent predictors of rigorous laboratory diagnosis, nor robustly estimated the performance of urinary dipsticks in a typical primary care population. Our aim was to estimate independent clinical and dipstick predictors of infection and develop clinical decision rules.
427 women presenting with suspected UTI in primary care had laboratory diagnosis assessed using the European Urinalysis guidelines standard. Independent clinical and dipstick predictors of diagnosis were estimated.
62.5% of women had confirmed UTI. Only nitrite, leukocyte esterase (+ or greater), and blood (haemolyzed trace or greater) independently predicted diagnosis (multivariate odds ratios respectively 6.36,4.52,2,23). A dipstick rule based on having nitrite, or both leukocytes and blood was moderately sensitive (77%) and specific (70%) (positive predictive value (PPV) 81%, negative predictive value (NPV) 65%). Predictive values were improved by varying the cut point: the NPV was 73% for all three-dipstick results being negative; the PPV 92% for having nitrate and either blood or leukocyte esterase. A 'clinical rule' based on having 2 of urine cloudiness, offensive smell, reported moderately severe dysuria, moderately severe nocturia - was less sensitive (65%) (Specificity 69%, PPV 77%, NPV 54%). The NPV was 71% for none of the four clinical features, and the PPV 84% for 3 or more features.
Simple decision rules could improve targeting of investigation or treatment. Strategies to use such rules will need to take account of their limited sensitivity, which is lower than expected from previous research.
|Session name:||XXIst ISTH Congress|
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