Referral, monitoring, and factors associated with non-referral of chronic kidney disease in Germany: a nationwide, retrospective cohort study.

Background: Chronic kidney disease (CKD) is one of the most significant drivers of the global burden of disease and an increasing public health issue. Adequate monitoring and referral of high-risk patients to nephrologists are associated with improved management of CKD. We aimed to assess nephrology referral rates, monitoring of kidney function, and factors associated with failure to refer in Germany. Methods: We retrospectively analyzed ambulatory claims data of 73,675,956 German patients who were covered by statutory health care in 2022, building a cohort of 1,301,122 patients who had at least two diagnoses of CKD stage 3-5 within the calendar year. In our analysis, we focused particularly on patients with CKD stage 4. Findings: We identified 207,043 patients with CKD stage 4, of which 134,143/207,043 (64.8%) received nephrologist treatment in 2022. The median age of the cohort was 82 years. Failure to quantify proteinuria occurred in 61,991/72,900 (85.0%) non-referred patients compared to 51,382/134,143 (38.3%) referred patients. In a mixed logistic regression model, referral was less likely for women (odds ratio [OR] 0.72, 95% confidence interval [CI] 0.71-0.74), higher age (OR per year 0.97, CI 0.96-0.97), nursing home inhabitants (OR 0.63, CI 0.61-0.65), and those with certain comorbidities. Regional factors (deprivation, population density, nephrologist density) were not associated with referral. Interpretation: A substantial proportion of patients with late-stage CKD are not receiving guideline-recommended kidney care in the German health care system, with disparities driven primarily by individual patient factors rather than geographical barriers. Funding: This study was funded by the University Hospital Schleswig-Holstein and the Central Research Institute of Ambulatory Health Care in Germany.