Diagnosis of urinary tract infection based on symptoms: how are likelihood ratios affected by age? a diagnostic accuracy study

OBJECTIVES: The aim of this study was to investigate the impact of age on the diagnostic properties of typical symptoms of urinary tract infection (UTI) in women presenting in general practice with symptoms suggestive of UTI with significant bacteriuria as the reference standard. DESIGN: Diagnostic accuracy study. SETTING: General practice, Copenhagen, Denmark. PARTICIPANTS: Adult 15 years or older. Women presenting in general practice with symptoms suggestive of UTI where urine was collected for investigation. PRIMARY AND SECONDARY OUTCOME MEASURES: Accuracy of four symptoms of UTI (dysuria, frequency, urge and abdominal pain) in six different age groups. RESULTS: 90 practices included 1178 adult women. The prevalence of bacteriuria varied between 30% in women aged 30–44 years and 67% in women aged 75–89 years. The likelihood ratios for dysuria varied between age groups with the best performance in women aged 15–29 (positive likelihood ratio (pLR): 1.62 (1.30–1.94), negative likelihood ratio (nLR): 0.36 (0.19–0.54)) and women aged 30–44 (pLR: 1.74 (1.30–2.17), nLR: 0.48 (0.27–0.68)). CIs included or approximated one for the remaining symptoms in most age groups. When symptoms were combined to calculate post-test probabilities, the combined effect of the varying prevalence of bacteriuria and the varying diagnostic values resulted in a large variation of the post-test probabilities between age groups. CONCLUSIONS: The diagnostic value of symptoms of UTI as well as the prevalence of bacteriuria in women presenting to general practice with suspected UTI vary between age groups with considerable clinical implications. Diagnostic studies should take demographics such as age into consideration. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov: NCT02698332.