Design and development of the MacTSQ measure of satisfaction with treatment for macular conditions used within the IVAN trial

Abstract

Background: The purpose of the study was to design a measure of patient satisfaction with treatment for macular disease, the MacTSQ, and to carry out psychometric evaluation of the measure. The measure was designed along the lines of the widely used Diabetes Treatment Satisfaction Questionnaire (DTSQ) and sister measures of treatment satisfaction for other conditions including diabetic retinopathy. Information was also gathered during in-depth interviews with 20 people who had experienced one of a range of treatments for macular degeneration. In a prospective study, the newly designed 16-item MacTSQ, was used in a multi-centre, randomised, double-blind clinical trial (the IVAN study) comparing two treatments for neovascular age-related macular degeneration and two treatment schedules: 1. continual monthly treatments (continuous arm), 2. initial 3 monthly treatments then monitoring and retreatment if necessary (discontinuous arm). The MacTSQ was administered after the first three treatments and at 12 and 24 months. Psychometric development was carried out using data from 137 patients. Sensitivity and validity of the MacTSQ were investigated using baseline and 12-month data. Results: Exploratory factor analysis yielded two subscales i) convenience, information and overall satisfaction (6 Items: Cronbach’s alpha = 0.740), and ii) safety, efficacy and discomfort (6 Items: alpha = 0.776). Twelve items also loaded on to a single scale (alpha = 0.815). Three items were removed from the scale but retained in the questionnaire for separate analysis where required. Greater satisfaction was reported at time 2 (12 months) than time 1 (after 3 monthly injections) on the safety, efficacy and discomfort subscale (W = 3000.500. p = 0.024, n = 108). Participants whose vision improved reported greater satisfaction than those who had no improvement e.g. U = 1599, p = 0.033. Those in the discontinuous arm reported greater satisfaction on subscale 1 than those in the continuous arm at time one (U = 1870, p = 0.04) and time 2 (U = 1132.5, p = 0.023). This finding suggested a better experience in the discontinuous arm. Conclusions: The MacTSQ will be valuable in investigating treatment satisfaction in clinical trials of new treatments or in a routine clinic situation and may highlight ways to improve patients’ experience of treatment.