ASSESSMENT AND TREATMENT OF METABOLIC ACIDOSIS IN JAPANESE PATIENTS WITH CKD: DATA FROM THE JAPAN CHRONIC KIDNEY DISEASE DATABASE EXTENSION (J-CKD-DB-EX)

Metabolic acidosis (MA) is common in patients with chronic kidney disease (CKD) and has been identified as a risk factor for CKD progression. It is also associated with adverse effects such as altered skeletal metabolism, insulin resistance, and protein-energy wasting. According to guidelines, both pharmacological therapy and dietary interventions aimed at reducing dietary acid load are recommended for the management of MA in CKD patients. However, reports from Western countries have suggested that MA is often underdiagnosed and undertreated. Meanwhile, the prevalence and management patterns of MA are different in Asian countries such as Japan, possibly because the dietary acid load is different from that in a typical Western diet, but the details remain unclear. This study aims to assess the serum bicarbonate measurement rate and the prevalence, diagnosis, and treatment rates of MA in Asian CKD patients.

This was a cross-sectional study using the Japan Chronic Kidney Disease Database Extension (J-CKD-DB-Ex), a nationwide electronic medical record database that collects data from 21 university hospitals across Japan. This study included patients with an estimated glomerular filtration rate (eGFR) between 15 and 60 mL/min/1.73 m² during the period from 2014 to 2021. The annual measurement rate of serum bicarbonate was calculated as the proportion of patients with at least one measurement per year. Among patients who had at least one serum bicarbonate measurement during the study period, we examined the prevalence of MA, which was defined as a serum bicarbonate level of <22 mEq/L or a prescription for sodium bicarbonate. The diagnosis of MA was identified by ICD-10 code and treatment was defined as the prescription of sodium bicarbonate. We also examined serum bicarbonate levels in treated and untreated patients.

The average annual number of patients was 58,010 during the period 2014-2021. During this period, the annual measurement rate of serum bicarbonate was consistently below 10%, ranging from 7.8% to 9.0%. Among 22,309 patients who had at least one serum bicarbonate measurement from 2014 to 2021, the overall prevalence of MA was 44.2%. Stratified by CKD stage, the prevalence was 31.8% in G3a, 46.4% in G3b, and 65.8% in G4. In patients with MA, the diagnosis and treatment rates were 8.6% and 7.5%, respectively. By CKD stage, the diagnosis rate was 4.8%, 6.9%, and 13.7% for G3a, G3b, and G4, respectively. The corresponding treatment rates were 3.6%, 5.2%, and 13.4%. Both the diagnosis and treatment rates were higher in patients with more advanced CKD stages. The mean serum bicarbonate value, based on the lowest recorded measurement during the study, was 18.81 mEq/L in the treated group and 22.10 mEq/L in the untreated group.

Based on nationwide real-world data, this study demonstrated that MA may be inadequately assessed and treated in Japanese patients with CKD, as indicated by low rates of serum bicarbonate measurement and of diagnosis and treatment of MA. Moreover, even in treated patients, the mean serum bicarbonate level remained low. This highlights the need for improved clinical management, including serum bicarbonate measurement and diagnosis, to enhance the treatment of MA through dietary and oral alkaline therapies, which may potentially benefit patients with CKD.