Validation of the kidney failure risk equation and its impact on referral strategies for chronic kidney disease: protocol for a retrospective cohort study using national claims and laboratory data in Thailand

Introduction:
Chronic kidney disease (CKD) is highly prevalent in Thailand and imposes a growing burden on the health system, driven by limited nephrology capacity and high rates of unplanned dialysis. The kidney failure risk equation (KFRE) estimates the risk of progression to kidney failure (KF) on age, sex, estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio. This study aims to validate and, if required, recalibrate the four-variable KFRE for the Thai population and to assess the potential impact of KFRE-guided referral strategies on clinical care and health system performance.

Methods and analysis:
We will conduct a retrospective cohort study using linked, de-identified national health databases covering approximately 70% of the Thai population. Adult patients with CKD stages 3–5 will be included. KFRE performance will be evaluated at 2 and 5 years for discrimination and calibration. If miscalibration is identified, the model will be recalibrated using Cox-based methods. Simulations (1000 iterations) indicated that approximately 920 KF events by 5 years would be required to achieve the target standard errors for the calibration slope. A subsequent impact analysis will compare KFRE-guided referral with current Thai CKD guideline criteria and real-world practice using a decision-tree and Markov modelling framework.

Ethics and dissemination:
Ethical approval was obtained from the Ethics Committee of the Institute for the Development of Human Research Protections, Thailand (COA No. IHRP2025110), Imperial College London and the London School of Hygiene and Tropical Medicine. The requirement for informed consent was waived due to the use of anonymised secondary data. Findings will be disseminated through peer-reviewed publications, conferences and policy briefs to supplement evidence-based referral strategies and health system planning.