Improving Urinary Tract Infection Diagnostics in Oncology: Reliability of Reflex Urine Culture in Immunosuppressed Neutropenic and Non-neutropenic Cancer Patients.

BACKGROUND: Urinary tract infections are prone to overdiagnosis, and reflex urine culture protocols offer a valuable opportunity for diagnostic stewardship in this arena. However, there is no recommended standard testing approach. Patients with cancer are often excluded from reflex urine culture protocols, especially if they are severely immunosuppressed or neutropenic. The aim of this study was to evaluate the performance characteristics of urine screening studies, including dipstick urinalysis for nitrite and leukocyte esterase and urine microscopy for white blood cell count, to detect significant pathogen growth.

METHODS: A retrospective study of 58 098 urine cultures with a paired dipstick urinalysis with or without urine microscopy was performed at Memorial Sloan Kettering Cancer Center in New York City, evaluating data from 1 January 2018 to 31 December 2020. A dipstick urinalysis was considered negative only if leukocyte esterase and nitrite were undetected.

RESULTS: A negative dipstick urinalysis had a negative predictive value of 98% for clinically significant bacteriuria in voided urine and 95% for catheterized urine. Notably, a negative urine dipstick test screen maintained a high negative predictive value among patients with neutropenia and in those with antibiotic exposure before testing. Finally, the presence of pyuria ≥10 white blood cells per high-power field on urine microscopy offered negligible incremental diagnostic benefit in samples with a negative dipstick urinalysis.

CONCLUSIONS: Reflex urine culture protocols contingent upon a screening dipstick urinalysis are a safe and effective platform for diagnostic stewardship in patients with cancer including those with neutropenia.