Analytical and clinical impact of bilirubin and glucose interference in Siemens Jaffé and enzymatic creatinine assays.

This study evaluated bilirubin and glucose interference in creatinine measurement using Jaffe (Crea_2) and enzymatic (ECre3) methods on Siemens' Atellica Solution system, to determine their clinical relevance and the potential need to transition to the enzymatic method. In-vitro interference studies were performed by spiking serum pools at the clinical decision level (115.0 μmol/L creatinine) with bilirubin (8.55-1078 μmol/L) and glucose (3.0-128.5 mmol/L). Additionally, 125 patient serum samples with varying bilirubin levels and 72 peritoneal dialysis samples with elevated glucose were analysed in parallel by both methods. eGFR, CKD stages, and MELD-Na scores were calculated to evaluate clinical impact. Method comparison used Passing-Bablok regression, Cohen's kappa, and non-parametric tests. The Jaffe method showed minimal bilirubin interference until 676 μmol/L, with significant negative bias at 1078 μmol/L (-20.72%). The enzymatic method showed a gradual negative bias but remained within ±10%. For glucose, Jaffe exhibited significant positive interference above 26.1 mmol/L, reaching +56.86% at 128.5 mmol/L, while the enzymatic method remained stable. Patient serum comparisons revealed excellent correlation across the bilirubin range (median difference - 2.4 μmol/L; R2 = 0.998; κ = 0.873). CKD stage differed between methods in 11/125 patients, with Jaffe yielding a more advanced stage in 10, whereas MELD-Na category changed in 4/125 patients. In peritoneal dialysis fluids, Jaffe results increased significantly with glucose concentration, while the enzymatic method remained unaffected. Siemens' Jaffe method can be clinically interchangeable with the enzymatic method across routine ranges, but targeted reflex testing with the enzymatic method for high-glucose (>21.9 mmol/L) or extreme bilirubin (>891.6 μmol/L) samples is recommended.