Mode of administration bias

Self-report questionnaires are widely used as proxy measures of clinical outcomes. The results of the questionnaires are typically tabulated into a single score and used to describe a selected construct or dimension of health (e.g. disability, function, pain).1,2 The recent increase in the popularity of self-report questionnaires has led to a concomitant increase in the validation of each instrument and the subsequent assessment of how bias can influence outcomes.3 According to Sackett and colleagues,4 bias is considered as any systematic deviation of an observation from the true clinical state. Unfortunately, bias associated with self-report questionnaires is quite common and can potentially influence the outcome of the targeted dimension of health.5 Minor variations in the structure of the questions of the self-report questionnaire (e.g. question wording and order) can lead to significant discrepancies in findings.6,7 Furthermore, variations in mode of administration (how, when, and in what manner the self-report questionnaire is provided) can also be a dramatic source of study bias.7,8 Different modes of administration include: (1) traditional paper and pencil self-administration ‘interview’ methods, handled through postal services, clinical administration, either in person of in absence of the clinician; (2) computer-assisted (electronic) self-administered ‘interview’ methods by use of a computerized interface; or (3) face-to-face verbal interviews between the patient and the clinician.9 Mode of administration bias occurs during data collection and involves intentional or unintentional alteration of information collected from the patient.8 When examining within-session effects of manual therapy interventions, mode of administration of outcomes measures is often either a written self-report assessment (such as a global rating of change score or a visual analog scale for pain) or a verbal report using a standardized outcomes measure. Studies that examine within-session or immediate effects routinely capture patient changes (either verbally or by written self-report) directly after a single intervention. How these measures are captured can lead to dramatically variable results.10 The goal of this editorial is to outline the potential forms of bias associated with mode of administration and to discuss methods to reduce the risk of inflated findings.