Evaluating the Effect of Questionnaire Context on the Reporting of Somatic Items Among People With Systemic Sclerosis

• BACKGROUND Most self-report depression symptom questionnaires include both psychological and somatic symptom items. The 9-item Patient Health Questionnaire (PHQ-9) and its 8-item version (PHQ-8) are commonly used depression assessment measures and include items that reflect the psychological and somatic symptoms of depression listed in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). However, there is concern that scores obtained using such questionnaires may be inflated in people with chronic illness due to the overlap of somatic symptoms related to depression and those stemming from their physical illness. In contrast to what might be expected, existing research suggests that having a medical illness or the severity of a respondent's medical illness are not associated with higher scores on somatic symptom items of the PHQ-9. Studies conducted in different patient populations, including people with systemic sclerosis (SSc), found either no significant differential item functioning (DIF) in somatic items of depression questionnaires or minimal DIF that did not significantly affect total questionnaire scores. It is possible that people with medical conditions who experience symptoms that may overlap with depression symptoms, including fatigue, changes in appetite, and sleep problems, do not report them on the PHQ-9 or PHQ-8 more than people without medical conditions due to a question ordering or context effect. The investigators will use the multinational Scleroderma Patient-centered Intervention Network (SPIN) Cohort to conduct a randomized experiment to examine whether awareness that depression symptoms are being assessed affects how people with a chronic illness report somatic symptoms of depression.
• OBJECTIVES The primary objective will be to evaluate differences in mean sum scores of PHQ-8 somatic items (sum of item 3 = sleep disturbances, item 4 = fatigue, and item 5 = changes in appetite) in people with SSc when the items are administered outside the context of a depression questionnaire compared to when they are administered in the context of a depression questionnaire. The secondary objective will be to evaluate differences in mean scores for each individual somatic symptom item.
• RECRUITMENT The SPIN Cohort is a large multinational cohort that collects longitudinal data on patient-reported outcomes from people living with SSc. It currently includes >1500 active participants recruited from 53 SPIN sites in Canada, the United States, Mexico, Australia, and France, Spain, and the United Kingdom. SPIN cohort participants are recruited during regular medical visits at SPIN recruitment sites, and written informed consent is obtained. Once enrolled in the Cohort, participants are sent an automated welcome email with instructions on how to activate their SPIN account and complete SPIN Cohort measures online. Cohort participants complete online assessments upon enrolment and at 3-month intervals. All SPIN Cohort participants who log in to the SPIN Cohort platform to complete a routine 3-month assessment will be included in this experiment.
• RANDOMIZATION The SPIN Cohort platform will be programmed to automatically randomize each participant via simple randomization in a 1:1 ratio to either the "Reordered items" arm or the "Original item order" arm.
• OUTCOMES The primary outcome variable will be the sum score of the 3 PHQ-8 somatic symptom item scores (item 3 = sleep disturbances, item 4 = fatigue, and item 5 = changes in appetite). The secondary outcome variables will be the individual item scores for items 3, 4, and 5.
• METHODS This is a two-arm parallel randomized controlled experiment. When SPIN Cohort participants log in to complete their routine assessment, they will be randomly assigned to complete either the standard PHQ-8 or a reordered version in which the 3 somatic symptom items (item 3 = sleep disturbances, item 4 = fatigue, and item 5 = changes in appetite) will be presented first, without any indication that they are part of a depression questionnaire, and the psychological symptom items will be presented later in the assessment protocol. Both primary and secondary analyses will be done as complete case analyses using between-groups t-tests.

Inclusion criteria

• SPIN Cohort patients must have a systemic sclerosis (SSc) diagnosis based on 2013 American College of Rheumatology/European League Against Rheumatism criteria confirmed by a SPIN physician, be ≥18 years old, be able to give informed consent, and be fluent in English, French or Spanish.
• Participants must have access to a computer or tablet with internet access.

Exclusion criteria

• None.