Using datasets to ascertain the generalisability of clinical cohorts: the example of European QUALity Study on the treatment of advanced chronic kidney disease (EQUAL).
Nephrol Dial Transplant 2021;
37:540-547. [PMID:
33426560 DOI:
10.1093/ndt/gfab002]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND
Cohort studies are among the most robust of observational studies but have issues with external validity. This study assesses threats to external validity (generalisability) in the European QUALity (EQUAL) study, a cohort study of people over 65 years with stage 4/5 chronic kidney disease.
METHODS
Patients meeting the EQUAL inclusion criteria were identified in The Health Improvement Network database and stratified into those attending renal units (secondary care cohort-SCC) and not (primary care cohort-PCC). Survival, progression to renal replacement therapy (RRT), and hospitalisation were compared.
RESULTS
The analysis included 250, 633, and 2,464 patients in EQUAL, PCC, and SCC. EQUAL had a higher proportion of men in comparison to PCC and SCC (60.0% vs. 34.8% vs. 51.4%). Increasing age (≥85 years odds ratio (OR) 0.25 (95% confidence interval (CI) 0.15-0.40)) and comorbidity (Charlson Comorbidity Index ≥ 4 OR 0.69 (CI 0.52-0.91)) were associated with non-participation in EQUAL. EQUAL had a higher proportion of patients starting RRT at 1 year compared to SCC (8.1% vs. 2.1%%, p < 0.001). Patients in the PCC and SCC had increased risk of Hospitalisation (incidence rate ratio=1.76 (95% CI 1.27-2.47) & 2.13 (95% CI 1.59-2.86)) and mortality at one year (hazard ratio=3.48 (95% CI 2.1-5.7) & 1.7 (95% CI 1.1-2.7)) compared to EQUAL.
CONCLUSIONS
This study provides evidence of how participants in a cohort study can differ from the broader population of patients, which is essential when considering external validity and applying to local practice.
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