Abstract
Background and Aims
The first phase of the published OPAL-HK study showed that Patiromer, an oral potassium binder, was effective at reducing serum potassium levels in patients with chronic kidney disease (CKD) stages 3 to 4. This phase was a 4-week, single-group treatment phase. Given the lack of a control arm, the aim of our study was to use real-world data from a large CKD cohort to provide a control comparison to evaluate the efficacy of Patiromer in normalising serum potassium.
Method
The initial phase of OPAL-HK comprised 243 patients with CKD G3-4 with a baseline serum potassium of 5.1 to <6.5mmol/L. To acquire a comparative matched cohort, patients were selected from the Salford Kidney Study (SKS), a prospective observational cohort study in the United Kingdom that has been recruiting patients aged ≥18 years old with CKD G3-5 since 2002. A 3-step process was applied to generate a propensity matched cohort. First, patients were chosen if they had an outpatient potassium level at any point after recruitment into SKS between 5.1mmol/L to <6.5mmol/L and whose next outpatient potassium level was checked 24 to 42 days (3.5 to 6 weeks) later (n=755). Second, all key OPAL-HK inclusion and exclusion criteria were applied. This left 162 patients who were then accurately matched in a 1:1 fashion to the 243 OPAL-HK patients using propensity score matching based on 6 baseline variables: age, gender, eGFR, diabetes mellitus, heart failure and potassium level. This produced a cohort of 87 SKS patients matched to their 87 OPAL-HK partner patients. We compared the two patient groups for the following OPAL-HK study endpoints: the mean change in serum potassium from baseline to follow-up at week 4, and the proportion of patients with a serum potassium of 3.8 to <5.1mmol/L at week 4.
Results
The groups were extremely well matched: between SKS vs. OPAL-HK, the mean (±SD) age was 63.9±13.3 vs. 63.7±9.5years (p=0.93); mean eGFR was 30.9±11.6 vs. 31.2±11.7ml/min/1.73m2 (p=0.85); 45 vs. 46 patients were diabetics (p=0.88); 29 vs. 24 had heart failure (p=0.41) and the mean potassium was 5.5±0.3mmol/L in both groups (p=0.68). The follow-up in the SKS cohort was 31±5 days.
At the end of follow-up, the mean potassium level remained 5.5±0.3mmol/L in SKS patients but had reduced to 4.5±0.5mmol/L in the OPAL-HK group (p<0.001), a mean (±SE) change of -1.00±0.06mmol/L. For the secondary endpoint, 74% of patients in OPAL-HK reached the target potassium range of 3.8 to <5.1mmol/L at week 4 compared with 0% from the comparator SKS cohort (see Figure).
Conclusion
Using real-world data as a tightly-matched control arm for the first phase of the OPAL-HK study, Patiromer is shown to be effective at reducing potassium levels in patients with CKD G3-4.
Real-world data in the United Kingdom: opportunities and challenges