Urinary ATP and bacteria in shed urothelial cells as a superior diagnostic marker for urinary tract infection in renal transplant recipients

Urinary tract infections (UTIs) cause complications for renal transplant recipients (RTRs) and may result in graft loss. Routine urinalysis to detect UTIs is insensitive/inaccurate in RTRs. UTI detection methods with greater accuracy are needed. A ≥50 nmol/l urinary ATP concentration indicates UTI and ATP measurement may be a superior diagnostic test (1). We investigated various urinalysis tests in 53 RTRs. ATP concentrations and intracellular bacteria (IB) in shed urothelial cells were compared to bacterial culture results. 22% of RTRs tested UTI positive by bacterial culture. IB were identified in 44% or RTRs, but only 2% IB positive were also UTI positive by bacterial culture. There was a significant association of the conventional bacterial culture with both urinary ATP concentration and evidence of IB (Fisher's exact test, p <0.05). 6% of RTRs had ATP concentrations ≥50 nmol/l. Those positive were also bacteria positive. 77% patients with ATP concentrations <50 nmol/l were negative by bacteria culture. Diagnostic odds ratios (DORs) indicated that ATP was a much stronger UTI indicator (DOR = 30.580) compared to IB (0.079). However combined urinary ATP concentration and evidence of IB was an even stronger diagnostic indicator of UTI (DOR = 105). Low urinary ATP concentration combined with absence of IB in shed urothelial may provide as superior diagnostic test for absence of UTI in RTRs. Funding: St Peter's Trust (UK).