Clinical value of cystatin C determination

It has been reported that cystatin C (cys-C) is elevated in patients with malignant disease. In order to investigate whether this phenomenon is linked to or independent of renal function, and at the same time examine the role of this marker in other pathological situations, cys-C concentrations were compared with 24-h creatinine clearance values in three groups of patients; the first group were undergoing treatment for malignant disease, the second group were renal transplant patients and the third randomly taken from patients for whom a routine creatinine clearance had been requested. Several patients with malignant disease had high cys-C levels without any correspondence to creatinine clearance values. Additionally, although cys-C shows a high sensitivity for detecting impaired glomerular function in renal transplant patients, the specificity was very low, with little discrimination being observed between patients with normal and pathological creatinine clearance levels. In other patients both the sensitivity and specificity of cys-C could be shown to be very good. Thus although cys-C can generally be recommended as a marker of the glomerular filtration rate, there are some patients for whom the clinical relevance is unclear.