The analytical change in plasma creatinine that constitutes a biologic/physiologic change

While all three of the creatinine methods studied had good precision, the ENZ method had the best precision, such that a change of 0.07 mg/dL (6 μmol/L) in serial creatinine concentrations up to 1.5 mg/dL on a patient could indicate a biologic change had occurred. For the alkaline picrate methods, a measured change of creatinine of 0.23 mg/dL for AP1 or 0.11 mg/dL for AP2 would indicate that a physiologic change in serum/plasma creatinine has occurred. While a definite biologic change may simply represent daily variations, detecting a biologic change in creatinine more rapidly could impact the ability of creatinine to detect early and clinically significant changes in renal function.