SCALE AND COSTS OF INTRODUCING CYSTATIN-C EGFR CALCULATIONS TO UK PRIMARY CARE

Introduction and Aims: The introduction of the CKD-EPI and cystatin-C testing has been recommended in recent CKD guidance. The cost impact of this has not been studied in a primary care CKD cohort. We evaluated the cost impact of these guideline changes for UK primary care. Methods: We analysed the baseline cohort of the PSP-CKD study, a large UK primary care CKD clinical trial. A laboratory calculated MDRD eGFR<60 ml/min/1.73m2 was the primary identifier for the cohort. Serum creatinine was also available. CKD-EPI (EPI) eGFR was recalculated from the serum creatinine. Costs were calculated using the criteria outlined in the 2014 NICE CKD guidance. Results: The records of 353,256 patients ≥18 years of age were analysed. 30,307 individuals had at least one MDRD eGFR<60ml/min/1.73m2 (‘eGFR<60’). 20,166 (66.5%) had ≥2 MDRD eGFRs<60, >3 months apart. Of those with a single MDRD eGFR<60, 27,598 (91.1%) had a re-calculated CKD-EPI (‘EPI’) eGFR<60. Table 1 shows the numerical breakdown of the reclassification, with percentages representing the proportion reclassified to eGFR>60. Reclassification to EPI eGFR>60 was less likely in those with pre-existing second MDRD eGFR<60 (3.3% versus 11.1%, p<0.001).To assess the numbers eligible for cystatin-C assay, we further analysed the 20,166 individuals with confirmatory MDRD eGFR<60. 12,142 (60.2%) had EPI stage 3A CKD. Within the EPI 3A group 7,153 (58.9%) had stage A1 proteinuria and were therefore eligible for cystatin-C assessment. 3055 (25.2%) had not had a urinary protein assessment.Extrapolating nationally, ~2% of the adult population could be eligible for a cystatin-C assay. Assuming similar results across the UK’s adult population and at a conservative cost of £5.50 (€7.50) per test, the initial cost of implementing cystatin-C testing across the eligible CKD population would be £5.8 million (€7.9 million). This estimate does not include costs of interpretation and consequent changes to clinical management. Conclusions: Based on a large primary care CKD cohort, CKD stage reclassification using EPI is relatively infrequent, and occurs less often if a confirmatory MDRD eGFR is available. Up to 2% of the adult population and 60% of the stage 3A CKD population could require a cystatin-C measurement. Conservative cost estimates for this are high and further cost-benefit considerations of cystatin-C testing may be helpful. Table 1: Reclassification 1 MDRD<60 ≥2 MDRD<60 Whole Cohort EPI<60 8,689 18,909 27,598 EPI>60 1,086 (11.1%) 662 (3.3%) 1,748 (6.0%) No serum creatinine 366 595 961 Total 10,141 20,166 30,307