The Patient and Treatment Characteristics of Kidney Transplant Recipients with a Clinically Relevant Jaffe/Enzymatic Serum Creatinine Difference

<b>Background:</b> Differences in serum creatinine (SCr) between the Jaffe and enzymatic methods affect the detection and staging of chronic kidney disease in kidney transplant recipients (KTRs). However, there are very limited data on the extent to which the detection of acute kidney injury (AKI) is affected, what impact immunosuppression can have and whether a KTR-specific estimated glomerular filtration rate (eGFR) formula is beneficial. <b>Methods:</b> A total of 12,081 parallel Jaffe/enzymatic SCr (eSCr) measurements of adult outpatient KTRs (61% male, median age 53 years) in the same serum sample at the University Hospital Essen (Germany) between January 2020 and October 2023 were evaluated. AKI and CKD were defined according to current KDIGO guidelines. The GFR was estimated using CKD-EPI and KTR-specific formulas. <b>Results:</b> In about 1% of all measurements and 5% of the KTR patients, the SCr difference between the two methods was ≥ 0.3 mg/dl. A total of 81% of these patients were male; the median age was 52 years. High levels of immunosuppression, including when Belatacept was used, did not seem to have a clinically relevant impact on the difference between Jaffe and eSCr. The KTR-specific eGFR formula generally showed a greater agreement between Jaffe and eSCr than the CKD-EPI eGFR formula, but they showed differences in the classification of CKD stages, especially in less severe stages. <b>Conclusions:</b> Clinically relevant SCr differences between Jaffe and SCr are rare and depend on the type of immunosuppression. A KTR-specific eGFR formula could be beneficial in some cases, but there are limitations in less severe CKD stages.