Cystatin C, mortality risk and clinical triage in US adults: threshold values and hierarchical importance.
BACKGROUND
It has been suggested that cystatin C may be a superior measure of estimated glomerular filtration rate (eGFR) than creatinine-based methods. We aimed to assess the utility of cystatin C for clinical triage in community-based settings.


METHODS
We identified cystatin C thresholds that maximize sensitivity and specificity (Max(Sn + Sp)) for predicting death and subsequently applied classification tree methodology considering serum creatinine, creatinine-based eGFR, urinary albumin-creatinine ratio and conventional modifiable risk factors to define subgroups, interactions and hierarchical ranks in fasting US adults (National Health and Nutrition Examination Survey 1988-94, followed through 2006).


RESULTS
A threshold cystatin C value of 0.94 mg/L exhibited the best maximum combined value of sensitivity and specificity for predicting death (Max(Sn + Sp), Sn 0.64/Sp 0.78). When all variables were considered jointly in a classification tree, cystatin C and albumin-creatinine ratio were the primary mortality discriminators in subgroups that added up to 41 and 14% of the study population, respectively; serum creatinine and creatinine-based eGFR were non-discriminatory.


CONCLUSIONS
Cystatin C may be useful for risk-based clinical triage in public health settings.
Foley
Robert N
RN
United States Renal Data System, Minneapolis, MN, USA. rfoley@cdrg.org
Wang
Changchun
C
Collins
Allan J
AJ
D000328:Adult; D000368:Aged; D002318:Cardiovascular Diseases / Q000378:metabolism / Q000401:mortality*; D003404:Creatinine / Q000097:blood; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000378:metabolism / Q000401:mortality*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000378:metabolism / Q000401:mortality*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012307:Risk Factors; D012680:Sensitivity and Specificity; D015996:Survival Rate; D014218:Triage
D055316:Cystatin C; D003404:Creatinine