Dipstick screening for urinary tract infection before arthroplasty: a safe alternative to laboratory testing?

We performed a prospective study on 247 consecutive patients attending our arthroplasty pre-admission clinic over six months, to compare the accuracy of dipstick urinalysis with the standard microbiological test for excluding urinary tract infection. There were 22 positive culture results and 43 positive dipstick results, with 16 true positives and 198 true negatives. Sensitivity was 72.7%, lower then the 88.0% figure for specificity. The positive predictive value was 37.2%, and the negative predictive value was 97.1%. Dipstick urinalysis is ideally suited to the busy pre-admission setting and would have resulted in a 90% reduction in the number of samples sent for laboratory analysis. In view of these results, we have changed our working practise from performing cultures to dipstick urinalysis on all patients prior to arthroplasty.