How Testing Drives Treatment in Asymptomatic Patients: Level of Pyuria Directly Predicts Probability of Antimicrobial Prescribing.

BACKGROUND: Urinalysis is a readily available test often used for screening. Pyuria is a common finding in asymptomatic patients, however, it is unknown how often identification of pyuria in the absence of confirmatory cultures leads to antimicrobial prescribing. Thus, the objective of this study was to measure the association between pyuria and antimicrobial initiation during the peri-operative period and to assess harms versus benefits of treatment. METHODS: A retrospective cohort of pre-operative patients within the national VA during the period from 10/1/08-9/30/13 who had a urinalysis performed during the 30-day pre-operative period was created; patients with positive urine cultures were excluded. The primary exposure was pyuria on pre-operative urinalysis. The primary outcome was antimicrobial initiation. Secondary outcomes included post-operative surgical (SSI), urinary tract (UTI), and C. difficile infections. Trend and logistic regression analyses were performed. RESULTS: Among 41,373 patients, 3,617 had pyuria. 887 (24.5%) pyuria patients received antimicrobials versus 1918 (5.1%) patients without pyuria. As the degree of pyuria increased, the odds of receiving antimicrobials also increased linearly (low pyuria, 14.7%, moderate pyuria, 24.0%, 37.4% high pyuria). Pre-operative pyuria was associated with post-operative C. difficile infections (aOR 1.7; 1.2-2.4); risk was higher in patients who received antimicrobials (aOR 2.4; 1.7-3.4). Pyuria was not associated with SSI but was associated with increases in UTI after orthopedic and vascular procedures; this risk was not mitigated by antimicrobial therapy. CONCLUSIONS: Urine screening during the pre-operative period is a low-value intervention that increases antimicrobial exposure but does not improve post-operative outcomes.