Outcomes

There were two co-primary outcomes in this survey: psychological distress, and trauma, as defined by the GHQ-12 and the IES-R respectively.

The GHQ-12 is a 12-item self-report measure devised to screen for psychological distress in the general population.29 The measure has high specificity and sensitivity, with reliability demonstrated across a range of populations.30 31 The GHQ-12 has been used in similar clinician-based studies measuring the psychological impact of infectious outbreaks and was chosen due to the brevity of the measure and its suitability for time-pressured medical staff.21 The GHQ-12 assesses current state and asks the participants to compare with usual state. GHQ-12 was asked at all three survey phases. Case-level distress is defined as a score of >3.30

The IES-R is a 22-item measure commonly used to measure post-traumatic stress following a prespecified traumatic incident and has been used to evaluate the impact of infectious disease outbreaks on hospital staff.21 32 It contains eight items that focus on ‘intrusion’, eight items on ‘avoidance’ and six items on ‘hyperarousal’. The IES-R was used at the peak and deceleration survey phases. A score of 24 or above indicates a clinically significant traumatic stress response, a score above 33 indicates best cut-off for a diagnosis of ‘probable post-traumatic stress disorder’ (PTSD).33 34

The secondary outcomes captured included personal and professional characteristics and their association with psychological distress and trauma. These personal and professional factors were identified through rapid literature review of high-quality systematic reviews and meta-analysis by experts in pandemic research.1 21–23 All factors identified as predictors of outcome were retained. This was supplemented by factors deemed of specific or emerging interest by the expert study steering committee. These were defined a priori in the study protocol, with the exception of ethnicity which was added during the peak survey due to the specific emergence of ethnicity as a potential marker of poor physical health outcomes.24