Improving UTI 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. Cancer patients are often excluded from reflex urine culture protocols, especially if 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 January 1, 2018, to December 31, 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 (NPV) of 98% for clinically significant bacteriuria in voided urine, and 95% for catheterized urine. Notably, a negative urine dipstick test screen maintained a high NPV 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.