Table 2. Survey measures

Concept	Measure	Description
Sociodemographic data	Age, sex, ethnic group, and employment status	Participants are asked to describe: age sex ethnic group (selecting from the list provided here: https://www.ethnicity-facts-figures.service.gov.uk/style-guide/ethnic-groups) employment status
Health status	a. PROMIS-10^26,27b. Self-reported long-term conditions	a. A validated 10-item person-centred measure of health and functioning for people with long-term conditions. The questions are a better fit for the study's purposes than those included in, for example, the SF-12.b. One question asks the participant to list the conditions they believe they have, which have lasted or will last longer than 6 months.
Treatment burden	a. The Multimorbidity Treatment Burden Questionnaire (MTBQ)⁷b. Novel short treatment burden questionnaire (STBQ)	a. The MTBQ is a concise, simply worded set of questions to measure treatment burden in people with MLTC-M. In this study, the 13-item questionnaire will be used.b. Building on previous work to develop a single-question screening measure for treatment burden,¹⁸ the STBQ has been developed with PPI input. It includes two questions: one to screen for high treatment burden, and one to understand what they find difficult from a range of options. The STBQ has been developed for use in clinical practice, rather than as a research tool. It may be revised in response to feedback from initial qualitative interviews.
Primary care experience	PCPCM²⁸	The PCPCM focuses on the patient’s access to care, relationship with the doctor or practice, and ability to reach health outcome goals. It comprises 11 items that form an evaluation of access, continuity, comprehensiveness, coordination, advocacy, family and community context, and goal-oriented care.
Health literacy	SILS²⁹	A validated single-item screening instrument, designed to identify patients with limited reading ability who need help reading health-related materials.
Healthcare use	Healthcare use³⁰	Five questions will be included, adapted from Salisbury and colleagues,³⁰ asking whether participants have recently stayed at an NHS hospital, visited A&E, and taken time off work to attend hospital and GP appointments.
Other		The survey may additionally include a small number of questions from other validated questionnaires if it is apparent from stakeholder work or initial qualitative work that any issues create treatment burden for patients which are not already included in the other data sources proposed.

A&E = accident and emergency department. MLTC-M= multiple long-term conditions (multimorbidity). MTBQ = Multimorbidity Treatment Burden Questionnaire. PCPCM = Person-Centered Primary Care Measure. PROMIS-10 = Patient-Reported Outcomes Measurement Information System. SF-12 = 12-Item Short Form Health Survey. SILS = Single Item Literacy Screener. STBQ = short treatment burden questionnaire.