Methods: Subjects with x-linked agammaglobulinemia (12), or common variable immunodeficiency (64), age 16 and above (mean 40 yrs) were included for study. All subjects were receiving immunoglobulin replacement therapy either by IV or SC. Subjects were able to read and speak English. Each site obtained approval from their respective IRBs. A modified questionnaire of 28 questions was created for the validation phase that was created by immunologists, nursing, and feedback from patients. After informed consent, patients completed the survey instrument, and were asked to complete a second survey within 48-120 hrs at home. Item reduction was done based on item distribution, and Rasch analysis.
Results: 214 surveys were collected on 76 subjects from 5 sites including demographic data. An interim analysis showed that a 3 point Likert-type scale was easier for patients to discriminate compared to a 5 point scale. A 28 item survey was reduced to 22 questions covering all of the SF-36 domains except body pain. Item reduction was based on those outfit items from the Rasch analysis, disordered items, lack of discrimination between the 3 point scale, and item overlap or duplication.
Conclusions: A PIDD specific HR-QOL survey questionnaire will provide clinicians with a tool for monitoring and evaluating Ig treatment in patients with PIDD.