MO495UNDERSTANDING INTERNATIONAL VARIATION IN KIDNEY FAILURE INCIDENCE: IMPACT OF DISPARITIES IN RAAS INHIBITOR PRESCRIPTION AND BLOOD PRESSURE CONTROL
Authors: Alencar de Pinho Natalia , Pecoits-Filho Roberto , Bieber Brian , Muenz Daniel , Lopes Antonio , Reichel Helmut , Combe Christian , Robinson Bruce , Stengel Benedicte 
Published: May 2021

Abstract

Background and Aims
Blood pressure (BP) control and renin-angiotensin-aldosterone system (RAAS) blockade are key measures to slow CKD progression, and the achievement of targets for these measures vary greatly across countries. We sought to evaluate to what extend this might explain international variations in kidney failure incidence.

Method
We used data from the CKD Outcomes and Practice Patterns Study (CKDopps), a cohort study of adult patients recruited from national samples of nephrology clinics. Patients with CKD G3 or G4, from Brazil (n=498), France (n=2702), Germany (n=2314), and the US (n=905) were included. Those neither with hypertension nor with albuminuria were excluded (n=103). We assessed systolic BP and RAAS inhibitor prescription at baseline, and their association with time to kidney failure, defined as an estimated glomerular filtration rate (eGFR) &lt; 15 ml/min/1.73m² or kidney replacement therapy initiation. Death was treated as a competing event. Cox proportional-hazards model was used to estimate cause-specific hazard ratios (cs-HR) and 95% confidence intervals (CI) for kidney failure according to country, before and after adjusting for systolic BP and RAAS inhibitor prescription, as well as demographics, and known risk factors for CKD progression.

Results
Median age (years) ranged from 67 in Brazil to 75 in Germany; and mean baseline eGFR (ml/min/1.73m²), from 27 in Germany to 33 in France. Prevalence of diabetes ranged from 20% in France to 36% in Brazil, and that of stage A3 albuminuria (&gt;300 mg/g), from 31% in Brazil to 44% in the US. Mean systolic BP (mm Hg) ranged from 132 in Brazil to 143 in France, and the percentage of patients prescribed RAAS inhibitor, from 58% in the US to 81% in Germany. After median follow-up of 4.0 (2.6-5.0) years, 1897 participants progressed to kidney failure and 522 died before meeting this outcome. Two-year crude cumulative incidence of kidney failure was the lowest in France (14%), where patients were recruited at an earlier CKD stage, and similar across Germany (25%), the US (26%), and Brazil (27%); that for all-cause death, the lowest in Brazil (2.5%), followed by France (3.4%), the US (4.4%), and Germany (4.6%). Sequential adjustment for demographics and progression risk factors, in particular baseline eGFR and albuminuria, significantly reduced the gap between France and the other countries (Figure). Despite the associations of systolic BP (cs-HR 1.14, 95%CI 0.95-1.38 for 120-129; 1.18, 95%CI 0.95-1.46 for 130-139; and 1.46, 95%CI 1.23-1.74 for ≥140 versus &lt;120 mm Hg) and RAAS inhibitor prescription (cs-HR 0.81, 95%CI 0.70-0.95 at 6 months of follow-up) with kidney failure, adjustment for these two treatment targets only marginally changed comparisons across studied countries.

Conclusion
In CKD patients under nephrology care, BP control and RAAS inhibitor prescription were associated with lower risk of kidney failure and substantially varied across countries. Despite this variation in practice, BP control and RAAS inhibitor prescription appear to explain little of the differences in risk of kidney failure by country.