A Risk Score to Guide Cystatin C Testing to Detect Occult-Reduced Estimated Glomerular Filtration Rate

Area of Science:

• Nephrology
• Clinical Chemistry
• Epidemiology

Background:

• Occult-reduced estimated glomerular filtration rate (eGFR<60 ml/min/1.73 m2) detected by serum cystatin C but missed by creatinine poses a high risk for complications.
• There is a need for tools to guide cystatin C testing among individuals with preserved kidney function based on creatinine (eGFRcreat>60 ml/min/1.73 m2).

Purpose of the Study:

• To develop and validate a risk score for identifying individuals with reduced eGFR by cystatin C (eGFRcys<60 ml/min/1.73 m2).
• To assess the utility of this risk score in guiding cystatin C testing in clinical practice.

Main Methods:

• Development of a risk score using logistic regression with Bayesian model averaging in the REGARDS study.
• External validation of the risk score in the NHANES III study.
• Assessment of performance using calibration and discrimination measures.

Main Results:

• Among 24,877 adults with eGFRcreat>60, 13.5% had reduced eGFRcys.
• Older age, Black race, smoking, higher BMI, lower eGFRcreat, diabetes, hypertension, and cardiovascular disease history were associated with reduced eGFRcys (p<0.001).
• The risk score achieved a c-statistic of 0.87 (REGARDS) and 0.84 (NHANES), identifying 72% of occult-reduced eGFR cases by screening only 22% of participants.

Conclusions:

• A risk score utilizing readily accessible clinical characteristics can effectively identify individuals with reduced eGFRcys missed by creatinine-based assessments.
• This tool can aid in targeted cystatin C testing, improving the detection of kidney function decline.