Establishing the criterion validity of self-report measures of adherence in hemodialysis through associations with clinical biomarkers: A systematic review and meta-analysis

Accurate measurement of adherence is crucial to rigorously evaluate interventions aimed at improving this outcome in patients undergoing in-center hemodialysis. Previous research has shown great variability in non-adherence rates between studies, mainly due to the use of different direct (e.g., clinical biomarkers) and indirect (e.g., questionnaires) measures. Although self-reported adherence in hemodialysis has been widely explored, it is still unclear which is the most accurate questionnaire to assess this outcome; therefore, the question of how to optimize adherence measurement in research and clinical practice has emerged as a key issue that needs to be addressed. This systematic review and meta-analysis aimed to explore the criterion validity of self-report measures of adherence in hemodialysis established through the association between test scores and clinical biomarkers (the criterion measure). The protocol was registered in PROSPERO (2021 CRD42021267550). The last search was performed on March 29(th), 2022, on Web of Science (all databases included), Scopus, CINHAL, APA PsycInfo, and MEDLINE/PubMed. Twenty-nine primary studies were included, and thirty-eight associations were analyzed. The Hunter-Schmidt’s meta-analysis was computed for the associations with more than two studies (n = 20). The results showed that six associations were large (16%), 11 were medium (29%) and the remaining were of small strength. The test scores from the End-Stage Renal Disease Adherence Questionnaire (range: 0.212<r(c) <0.319) and the Dialysis Diet and Fluid Non-Adherence Questionnaire (range: 0.206<r(c) <0.359) had medium to large strength associations with interdialytic weight gain, serum phosphorus, and potassium levels, indicating that these questionnaires have reasonable concurrent criterion validity to measure fluid control and adherence to dietary restrictions in patients receiving hemodialysis. The available data did not allow exploring the criterion validity of the test scores in relation to hemodialysis attendance (skipping and/or shortening sessions). These results suggest that the decision to use one questionnaire over another must be made with caution, as researchers need to consider the characteristics of the sample and the objectives of the study. Given that direct and indirect methods have their advantages and disadvantages, the combination of adherence measures in hemodialysis is recommended to accurately assess this complex and multidimensional outcome.