Renal function overestimation in underweight and/or non-ambulatory patients.

Creatinine clearance estimation is widely used to evaluate the renal function of the patients in order to initiate or adjust the drugs dosage. However serum creatinine, as a muscle metabolism by-product, may not be a reliable parameter in underweight and/or non-ambulatory patients, such as geriatric, acquired immunodeficiency syndrome patients and bed-confined and cachexic cases. To avoid overestimation of the renal function in those patients, serum cystatin C can be considered as a sensitive and accurate alternative for serum creatinine.