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Table 7 Sampling for maximum variation when using TDF to understand influences on behaviour

From: A guide to using the Theoretical Domains Framework of behaviour change to investigate implementation problems

Study title
 A study of the perceived risks, benefits and barriers to the use of selective decontamination of the digestive tract (SDD) in adult critical care units
Rationale for changing behaviour
 Critically ill patients who require management in an Intensive Care Unit (ICU) are particularly susceptible to hospital acquired infections which are associated with high morbidity and mortality. SDD may reduce these infections and improve mortality but has not been widely adopted into practice. Adoption of SDD would involve a set of protocolised behaviours performed by a range of healthcare professionals, so this investigation sought the views of multiple professional stakeholders.
Study design and materials
 A four-phase study in three regions (the UK, Canada and Australia/New Zealand) of which Phase 2 was a Delphi study. Round 1 of the Delphi study involved one-to-one telephone interviews based on the TDF. Four key clinician groups (ICU physicians, ICU pharmacists, infectious disease clinicians/medical microbiologists, ICU clinical leads/nurse managers) were sampled using databases within each region. The researchers aimed for 10 from each group in each region. Purposive diversity sampling was used to identify a wide range of views, based on the following variables:
• Hospital is academic-affiliated or not
• Years of experience (time working in intensive care)
• Size of ICU (number of beds)
• Current practice (routinely perform SDD or not)
 Potential participants were ranked according to these variables and invited to participate in the Delphi study based on their ranking. During the interview phase, diversity on these factors was tracked using a diversity sampling table.
Findings and conclusions
 141 participants were interviewed. Beliefs about Consequences was the most populous domain. “SDD increases antibiotic resistance”, “SDD reduces Ventilator Associated Pneumonia” and “SDD benefits the patients to whom it is delivered” were the most frequently mentioned beliefs, illustrating the problematic balance between potential harms and benefits.
Study outputs
 Cuthbertson et al. [75, 76]; Dombrowski et al. [77]; Francis et al. [78]; Duncan et al. [79]; Marshall et al. [80]