Adaptation and validation of the Treatment Burden Questionnaire (TBQ) in English using an internet platform

Background: Treatment burden refers to the workload imposed by healthcare on patients, and the effect this has on quality of life. The Treatment Burden Questionnaire (TBQ) aims to assess treatment burden in different condition and treatment contexts. Here, we aimed to evaluate the validity and reliability of an English version of the TBQ, a scale that was originally developed in French. Methods: The TBQ was translated into English by a forward-backward translation method. Wording and possible missing items were assessed during a pretest involving 200 patients with chronic conditions. Measurement properties of the instrument were assessed online with a patient network, using the PatientsLikeMe website. Dimensional structure of the questionnaire was assessed by factor analysis. Construct validity was assessed by associating TBQ global score with clinical variables, adherence to medication assessed by Morisky's Medication Adherence Scale (MMAS-8), quality of life (QOL) assessed by the PatientsLikeMe Quality of Life Scale (PLMQOL), and patients' confidence in their knowledge of their conditions and treatments. Reliability was determined by a test-retest method. Results: In total, 610 patients with chronic conditions, mainly from the USA, UK, Canada, Australia, or New Zealand, completed the TBQ between September and October 2013. The English TBQ showed a unidimensional structure with Cronbach a of 0.90. The TBQ global score was negatively correlated with the PLMQOL score (r(s) = -0.50; p < 0.0001). Low rather than moderate or high adherence to medication was associated with high TBQ score (mean [SD] TBQ score 61.8 [30.5] vs. 37.7 [27.5]; P < 0.0001). The treatment burden was higher for patients who had insufficient knowledge compared with those who had sufficient knowledge about their treatments (mean +/- SD TBQ score 62.3 +/- 31.3 vs. 47.8 +/- 30.4; P < 0.0001) and conditions (63.0 +/- 31.6 vs. 49.3 +/- 30.7; P < 0.0001). The intraclass correlation coefficient for the retest (n = 282) was 0.77 (95% CI 0.70 to 0.82). Conclusions: We found that the English TBQ is a reliable instrument in this population, and provide evidence supporting the construct validity for its use to assess treatment burden for patients with one or more chronic conditions in English-speaking countries.