Intra-individual variation in creatinine and cystatin C

BACKGROUND: Serum creatinine and cystatin C are measured in the assessment of glomerular filtration rate. Biological variation of an analyte is an important determinant of its usefulness. Intra-individual variation in serum creatinine and cystatin C in healthy subjects was determined in this study. METHODS: Weekly blood samples were taken from 10 healthy subjects and analysed for creatinine (kinetic Jaffe method) and for cystatin C (by nephelometry). RESULTS: Intra-individual variations for serum creatinine and cystatin C were 6.1% and 4.55%, respectively. Index of individuality values were similar for the analytes (0.35 for both). CONCLUSION: Intra-individual variations for serum creatinine and cystatin C were similar in healthy subjects.