CST3 and chronic kidney disease: Similarly, using eGFR < 90 ml/min/1.73m2 cut-off, the highest prevalence was with the Schwartz cystatin C equation that showed a 58.9% (95% CI: 54.4–63.3%) prevalence of kidney impairment and a 23% (95% CI 19.2–26.8%) prevalence of CKD.