Falsely-elevated serum creatinine values in diabetic ketoacidosis -- clinical implications

Area of Science:

• Clinical Chemistry
• Nephrology
• Endocrinology

Background:

• Diabetic ketoacidosis (DKA) is often associated with elevated serum creatinine (S-CR).
• The Jaffe end-point reaction method for S-CR measurement can be affected by acetoacetate, a common byproduct in DKA.
• Kinetic assay methods are reportedly unaffected by ketone interference.

Purpose of the Study:

• To investigate the interference of acetoacetate on serum creatinine measurements in patients with diabetic ketoacidosis.
• To compare S-CR values obtained using end-point versus kinetic assay methodologies in DKA patients.
• To determine if elevated S-CR in DKA necessarily indicates renal impairment.

Main Methods:

• Studied 18 patients with diabetic ketoacidosis.
• Measured serum creatinine (S-CR) using both the end-point Technicon SMA 6/60 method (Group A, 10 patients) and the kinetic DuPont ACA method (Group B, 8 patients).
• Correlated "excess anion gap" with S-CR in Group A patients.

Main Results:

• Significantly higher S-CR values were observed in Group A (3.3 +/- 1.1 mg/dl) compared to Group B (1.6 +/- 0.24 mg/dl) (P < 0.01).
• A significant positive correlation (r = +0.81, p < 0.01) was found between "excess anion gap" and S-CR in Group A.
• Serial measurements in two patients further supported analytical interference from ketones.

Conclusions:

• Elevated S-CR in DKA patients using end-point methods may be due to analytical interference, not necessarily renal impairment.
• Kinetic assay methods provide more accurate S-CR measurements in DKA, free from ketone interference.
• Verification of S-CR with a kinetic method is recommended for DKA patients to avoid misinterpretation of renal function.