Development and validation of the Multimorbidity Treatment Burden Questionnaire
Treatment burden is a patient’s perception of the effort required to self-manage their medical conditions and the impact this has on their general wellbeing (e.g. taking complex medication regimens, co-ordinating health care appointments, making lifestyle changes, and self-monitoring their conditions). There are four existing questionnaires that measure treatment burden for patients with multimorbidity, all of which have important limitations, highlighted in the recent National Institute for Health and Care Excellence Multimorbidity guideline. We set out to develop and validate a new scale – the Multimorbidity Treatment Burden Questionnaire (MTBQ).
The content of the scale was based on a review of the qualitative literature and views from a patient and public involvement group. Iterative cognitive interviews assessed content validity. The scale was piloted and the final version was tested in a large study of adults with three or more long term conditions. For each question we examined the proportion of missing data and ‘does not apply’ responses, and the distribution of responses. Factor analysis, Cronbach’s alpha and Spearman’s rank correlations assessed dimensional structure, internal consistency reliability and construct validity respectively. Responsiveness to change was assessed by calculating the effect size between baseline and nine-month follow-up. We tested the pre-specified hypothesis of a greater effect size in participants with an improvement in quality of life score compared with no improvement. We assessed interpretability of the questionnaire by grouping the global MTBQ scores into tertiles and comparing participant characteristics across these categories.
The MTBQ was completed by 1546 elderly participants (average age 71 years) with three or more long term conditions. Cognitive interviews found good acceptability and content validity. Factor analysis supported a one factor solution. Cronbach’s alpha was 0.83. We found high floor effects with 22% of participants scoring a global MTBQ score of zero. All of the existing treatment burden scales have found similarly high floor effects and a greater floor effect was found for the comparator treatment burden scale with 54% of participants scoring zero. In accordance with the pre-specified hypotheses, the global MTBQ score had a positive association with the comparator treatment burden scale (rs 0.58, p<0.0001) and with the Bayliss disease burden scale (rs 0.43, p<0.0001) and a negative association with quality of life scale (rs -0.36, p<0.0001). A significant effect size of -0.30 was found in participants with a positive change in quality of life score. Patients with depression, dementia and rheumatoid arthritis were more likely to have high treatment burden scores.
The MTBQ scale is a ten-item measure of treatment burden for patients with multimorbidity that has demonstrated good content validity, construct validity and internal consistency reliability. It is a useful research tool for assessing the impact of interventions on treatment burden for patients with multimorbidity.