Creatinine-based eGFR accuracy is severely compromised by urgent care pharmacotherapy: real-life evidence and implications for emergency service clinical practice

Background: Assessment of kidney function in emergency settings is essential across all medical subspecialties. Daily assessment of patient creatinine result from emergency medical services showed that some creatinine results apparently deviated from expected creatinine values implying occurrence of drug-related interferences. Methods: Real-time clinical evaluation of an enzyme method (Roche CREP2) in comparison to Jaffé gen. 2 method (Roche CREJ2) was performed. During the period of December 2022 and January 2023 we analyzed 8498 paired patient specimens, 5524 were heavily medicated STAT patient specimens, 500 were pediatric specimens and 2474 were analyzed in a distant general population in a different region using the same methods. Results: About 2 percent of hospital specimens with patient history showed apparent drops of creatinine concentrations with the enzyme method against the compensated Jaffé method. Suspect medication was found in 43 out of 46 reviewed patients where medication data were allowed for review. A general patient cohort showed no drops of concentrations measured by the enzyme method. Pediatric hospital cohort showed 6 drops out of 500 total measurements. Conclusions: We implemented immediate corrective measures that were replacement of enzyme creatinine with Jaffé gen.2 method, the “full Schwartz” composite formula for pediatric medicine and CKD-EPI with cystatin C for STAT adult medical services. We conclude that pharmacotherapy-induced inaccuracies with enzyme creatinine methods imply the need for proper method validations in the relevant patient population and may facilitate introduction of cystatin C to emergency medicine clinical practice.