Psychometric evaluation of the functional assessment of HIV Infection (FAHI) questionnaire and its usefulness in clinical trials

Abstract

To evaluate psychometric properties of the Functional Assessment of Human Immunodeficiency Virus Infection (FAHI) questionnaire, a 47-item disease-specific instrument evaluating Health-Related Quality of Life (HRQL) in human immunodeficiency virus (HIV)-infected patients. Treatment-experienced HIV-infected patients from two clinical programmes (N = 565; N = 1,096) completed the FAHI at Baseline and after 24 weeks of treatment. Psychometric properties of the FAHI were assessed in both trial populations, including minimal important differences (MIDs) calculations. Links between HRQL assessed by FAHI Total score, and biological endpoints were explored by regression analysis and mean score comparisons. Cronbach’s alphas ranged from 0.72 to 0.94. Most items met convergent and discriminant validity criteria. Better FAHI scores were seen for patients in earlier HIV stages. Responsiveness was demonstrated with changes in FAHI scores significantly linked to change in EQ-5D score. Depending on methods used, MIDs ranged from 3.2 to 14 for FAHI Total score. Small association was found between FAHI Total score and CD4 count and viral load (r-square < 3%). Mean changes in FAHI scores were not statistically related to viral response. The FAHI demonstrated acceptable psychometric properties in two independent populations. HRQL assessment enabled detection of changes in patients’ health status not revealed by traditional efficacy endpoints.