Purpose: This study compared the measurement properties for multiple modes of survey administration, including postal mail, telephone interview, and Web-based completion of patient-reported outcomes (PROs) among survivors of childhood cancer.
Methods: The population included 6,974 adult survivors of childhood cancer in the Childhood Cancer Survivor Study who completed the Brief Symptom Inventory-18 (BSI-18), which measured anxiety, depression, and somatization symptoms. Scale reliability, construct validity, and known-groups validity related to health status were tested for each mode of completion. The multiple indicators and multiple causes technique was used to identify differential item functioning (DIF) for the BSI-18 items that responded through a specific survey mode. The impact of the administration mode was tested by comparing differences in BSI-18 scores between the modes accounting for DIF effects.
Results: Of the respondents, 58%, 27%, and 15% completed postal mail, Web-based, and telephone surveys, respectively. Survivors who were male; had lower education, lower household income, or poorer health status; or were treated with cranial radiotherapy were more likely to complete a telephone-based survey compared with either a postal mail or Web-based survey (all P < .05). Scale reliability and validity were equivalent across the 3 survey options. One, 2, and 5 items from the anxiety, depression, and somatization domains, respectively, were identified as having significant DIF among survivors who responded by telephone (P < .05). However, estimated BSI-18 domain scores, especially depression and anxiety, between modes did not differ after accounting for DIF effects.
Conclusion: Certain survivor characteristics were associated with choosing a specific mode for PRO survey completion. However, measurement properties among these modes were equivalent, and the impact of using a specific mode on scores was minimal.