Table 1.

Thematic coding framework

Key theme	Code	Description/notes
Factors influencing acceptance of testing
Importance of avoiding self-isolation	Negative impact of isolation on physical and mental health	Impact of isolation on both self and family
	Negative impact of isolation on work/income	Particularly among those unable to work remotely or earn a wage during periods of isolation
	Low impact	For example, people who were able to work remotely, had excellent support networks, and were content to spend time at home/alone
Confidence in test results	Estimated accuracy of test	Estimates (usually in percentages) of lateral flow test accuracy
	Repeat testing to increase accuracy	Multiple LFT / PCR tests to confirm / increase perceived accuracy
	Experience of dis-concordant results	Either direct experience or vicarious experience of negative LFT and positive PCR
	Good enough / better than nothing	Whilst acknowledging limitations, viewing testing as better than nothing
Perceived risk of infection	Exposure /proximity to case	Captures claims about distance/location/environment in which contact occurred
	Lack of symptoms	Participants’ belief that they are not infected due to a lack of symptoms
	Impact of vaccine	Participants’ belief that they are unlikely to be infected due to having had the vaccine
	Impact of belief on perceived need for isolation	Perceived (lack of) infection reducing motivation for isolation
Perceived risk of transmission	Risk of transmission	Captures anxieties regarding the potential for transmission to others (even if perceived risk of infection is low)
	Exposure to vulnerable individuals	Regular contact with vulnerable individuals increased concerns regarding risk of transmission
Knowledge and understanding
Use of tests	How to use tests	Participants’ awareness and confidence for testing themselves correctly
	When to use tests	Understanding of when to use each test and why
Rules and regulations of DCT		Receipt and interpretation of rules and regulations
Impact of test results
Maximising adherence		Testing as a way of encouraging people to isolate when they have a positive test result
Avoiding isolation	Avoiding unnecessary isolation	Including any comments about unnecessary isolation
	Low-risk/essential activities	Includes quotes about low-risk (e.g., zero contact) or essential (but possibly with contact) activities. Also includes comments about attempts to reduce risk during these activities
	Facilitating return to normality	Including comments about testing as a possible way of reducing the need for isolation and facilitating a return to normal
Reassurance and peace of mind	Reassurance	Comments about feeling relieved and/or reassured by test results
	Potential for engagement in high-risk activities	Potential high-risk contact following negative test results (by both self and others)
Alternative use of testing
Use of tests outside trial		Comments about how participants have / regularly use tests
Use of tests in PCR group		Comments about use of lateral flow testing among participants in the PCR group – including risk of non-adherence following negative test results
Initial contact with NHS test and trace
Understanding /acceptance of test and trace		Comments by participants about not being contacted by NHS test and trace, or not believing communication to be genuine
Understanding of study procedures		Any comments regarding a lack of clarity regarding study procedures (e.g., lack of clarity regarding group allocation)