Creatinine determination in peritoneal dialysis: what method should be used?

Area of Science:

• Nephrology
• Clinical Chemistry
• Biomedical Engineering

Background:

• Accurate creatinine measurement is crucial for assessing continuous ambulatory peritoneal dialysis (CAPD) adequacy and patient nutritional status.
• Common creatinine assays, Jaffe's reaction and enzymatic methods, are susceptible to glucose interference, especially in dialysate.
• High-pressure liquid chromatography (HPLC) is a potential reference method for creatinine determination.

Purpose of the Study:

• To compare the accuracy of Jaffe's reaction, enzymatic method, and HPLC for creatinine measurement in plasma, urine, and dialysate from CAPD patients.
• To evaluate the impact of glucose interference on creatinine assays in dialysis solutions.
• To determine the most reliable method for monitoring CAPD patients.

Main Methods:

• Creatinine levels were measured using Jaffe's reaction, enzymatic assay, and HPLC.
• Calibration curves were prepared using dialysis solutions with varying glucose concentrations.
• Analysis included plasma, urine, and dialysate samples from 40 CAPD patients.

Main Results:

• Jaffe's reaction and enzymatic methods showed high intercepts in glucose-containing dialysis solutions, indicating interference.
• HPLC consistently yielded lower creatinine values in plasma, urine, and dialysate compared to the other methods.
• Jaffe's and enzymatic methods showed comparable results in plasma and urine, but enzymatic methods were affected by glucose in dialysate.

Conclusions:

• HPLC is the reference method for creatinine measurement in CAPD patients due to its accuracy and lack of glucose interference.
• While Jaffe's and enzymatic methods can be used for plasma and urine, careful consideration of glucose interference is needed for dialysate.
• Consistent use of a single creatinine assay method is essential for reliable patient monitoring (creatinine clearance, lean body mass).