Cystatin C improves the detection of mild renal dysfunction in older patients.
BACKGROUND
Conventional estimates of glomerular dysfunction, including serum creatinine and creatinine clearance, are inadequate in older people. In this study we have compared the diagnostic accuracy of a novel test of kidney disease, cystatin C, against these markers in older patients with a range of renal function.


METHODS
Fifty-three patients (mean age 79.6 years, range 69-92 years) with a variety of medical diagnoses were recruited via outpatient clinics. Exclusion criteria included active rheumatoid disease, known current malignancy, renal replacement therapy/renal transplantation and cognitive impairment. (51)Cr-EDTA was used as the reference method against which the other markers of glomerular filtration rate were compared using regression analyses.


RESULTS
The best fit with glomerular filtration rate was given by Cockcroft and Gault calculated clearance (R(2) = 0.83), followed by serum cystatin C (R(2) = 0.79), serum creatinine (R(2) = 0.76) and creatinine clearance (R(2) = 0.73). The accuracy for glomerular filtration rate prediction was poor for all markers. Serum cystatin C detected nearly all patients with mild renal impairment whereas serum creatinine only detected half of these cases. Regression modelling predicted that the upper limit of normal for serum cystatin C would be exceeded as glomerular filtration rate fell below 64 mL/min/1.73 m(2), compared with 44 mL/min/1.73 m(2) for serum creatinine.


CONCLUSIONS
Serum cystatin C is a simple and sensitive screening test for kidney dysfunction in older people.
O'Riordan
Shelagh E
SE
Department of Health Care of the Older Person, East Kent Hospitals NHS Trust, Kent and Canterbury Hospital, Canterbury CT1 3NG, UK.
Webb
Michelle C
MC
Stowe
Helen J
HJ
Simpson
David E
DE
Kandarpa
Madhu
M
Coakley
Anthony J
AJ
Newman
David J
DJ
Saunders
Jean A
JA
Lamb
Edmund J
EJ
D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D003430:Cross-Sectional Studies; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D004492:Edetic Acid; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000097:blood* / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D012016:Reference Values; D012680:Sensitivity and Specificity; D044465:White People
D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D004492:Edetic Acid