Internal consistency reliability of the Revised Illness Perceptions Questionnaire: A systematic review and reliability generalization meta-analysis

The Revised Illness Perception Questionnaire (IPQ-R) assesses patients' perspectives of their illnesses. Original psychometric testing occurred in limited populations. The purpose of this reliability generalization meta-analysis was to: (1) estimate internal consistency reliability of each IPQ-R subscale, and (2) test moderators of these estimates. Web of Science was searched in July 2022 for articles citing the original IPQ-R paper that reported IPQ-R reliability data. Cronbach's alphas (alpha) were pooled for each IPQ-R subscale using inverse variance weighting and DerSimonian and Laird estimation. Sixty-six studies met criteria. Overall pooled alpha estimates were acceptable: 0.71-0.87. Treatment control reliability was reduced among cardiac (alpha = 0.68), diabetes/kidney disease (alpha = 0.63), and mixed/other (alpha = 0.66) samples; cyclical reliability was reduced in cancer (alpha = 0.65) samples. Age, gender, and race were also significant moderators. Subscale reliability varied based on sample characteristics. Adapting IPQ-R subscales to account for sample variation could improve measurement of illness perception constructs.