Optimising referrals from primary care to renal clinics. Findings from a Welsh population study

Problem

Recently in the UK, the kidney failure risk equation (KFRE) to predict the risk of kidney failure has been incorporated into clinical guidelines. Referral from primary care to a specialist renal clinic is recommended if eGFR falls to <30ml/min/1.73m2 and/or if the five-year KFRE is greater than 5%. A new race-free estimated glomerular filtration rate (eGFR) was developed in 2021. We investigate the impact of using the race-free eGFR equation and KFRE on chronic kidney disease (CKD) diagnosis in primary care and potential referrals to the renal clinic.

Approach

Primary care records for 79% of the population of Wales (UK) are held in the electronic health records repository Secure Anonymised Information Linkage Databank (SAIL). We studied serum creatinine values and urine albumin-creatinine ratios (uACRs) from 1st January 2013 to 31st December 2020. We calculated eGFR values using three equations: MDRD, CKD-EPI 2009 and (race-free) CKD-EPI 2021. Using the different equations, we compared the numbers of patients with incident eGFR <60ml/min/1.73m2 and incident eGFR <30ml/min/1.73m2. For each year from 2013 to 2020, we identified the patients with prevalent eGFR 30-60ml/min/1.73m2, those with annual uACR testing and those who met referral criteria by A) eGFR decline and B) KFRE without eGFR decline.

Findings

There were 121,471 patients with prevalent CKD between 2013 and 2020. eGFR values were lowest using the MDRD equation (median 47.1ml/mi/1.73m2, IQI 39.7-51.9) and highest with the CKD-EPI 2021 equation (median 50.0ml/min/1.73m2, IQI 41.6-55.3). Changing between these two equations would have led to a 17.6% reduction in incident eGFR<60ml/min/1.73m2 and a 7.5% reduction in incident eGFR<30 between 2013 and 2020. The rate of annual uACR testing fell from 46.3% in 2013 to 25.3% in 2019. eGFR and uACR testing were reduced further in 2020 during the Covid-19 pandemic. Patients without diabetes and older patients were the least likely to have had uACR testing at any time. In 2019 (the last year before the Covid-19 pandemic), 787/61,721 (1.3%) patients with CKD stage 3 met referral criteria by eGFR decline and and additional 587 (1.0%) by KFRE without eGFR decline.

Consequences

KFRE can be used to identify a significant number of patients at heightened risk of kidney failure. Annual uACR testing rates are low, especially in those without diabetes and in older adults. eGFR and uACR testing were markedly reduced during the Covid-19 pandemic in 2020 as most routine disease monitoring stopped. Expanding uACR testing in primary care and using KFRE may improve the identification of individuals at risk of progressive kidney disease, but this is challenging during the Covid-19 pandemic. Using the race-free eGFR equation will reduce diagnoses of incident eGFR<60 and therefore the numbers of patients requiring monitoring of blood and urine tests and blood pressure.