The clinical utility and cost impact of cystatin C measurement in the diagnosis and management of chronic kidney...

Area of Science:

• Nephrology
• Clinical Chemistry
• Public Health

Background:

• Creatinine-based estimates of glomerular filtration rate (GFR) can lead to over-diagnosis of chronic kidney disease (CKD).
• Guidelines recommend cystatin C-based GFR estimates to confirm CKD in specific cases (GFR 45-59 ml/min/1.73 m2 without albuminuria).
• The utility of cystatin C in primary care for CKD diagnosis has not been evaluated.

Purpose of the Study:

• To evaluate the impact of using cystatin C-based eGFR in primary care for diagnosing and managing CKD.
• To assess its effect on CKD classification, risk prediction, and healthcare costs.

Main Methods:

• Compared creatinine-based (eGFRcreat) and cystatin C-based (eGFRcys) GFR estimates in 1,741 primary care patients over 5 years.
• Analyzed reclassification of CKD G3aA1 patients, impact on risk prediction models, and cost implications of implementing guidelines.

Main Results:

• Mean eGFRcys was significantly lower than mean eGFRcreat.
• Cystatin C reclassified 7.7% of CKD G3aA1 patients to eGFR ≥ 60 ml/min/1.73 m2, but 59.0% to a more advanced CKD category.
• eGFRcys identified more CKD progression (18.2% vs 10.5%) but did not improve risk prediction models.
• Implementing guidelines increased monitoring costs by approximately £31 million annually in England.

Conclusions:

• Using cystatin C in primary care resulted in minimal reduction in diagnosed CKD but identified more advanced disease.
• Cystatin C-based eGFR did not enhance risk prediction and incurred higher costs.
• Current guidelines for cystatin C testing may not be suitable for primary care implementation.