A post-discharge quality of life outcome measure for lower limb amputees: test-retest reliability and construct validity

Objective: To adapt the Patient Generated Index (PGI) quality of life measure for use with lower limb amputees and to conduct a test-retest reliability and construct validity study on the adapted measure. Design: Repeat questionnaire interviews with a four-week interval administered by trained peers. Setting: Participants' homes. Subjects: Forty-two unilateral lower limb transfemoral amputees, 16 years of age or older and fluent in English, fitted with a prosthesis and discharged into the community for at least one year following postoperative rehabilitation therapy. Main results: An intraclass correlation coefficient of 0.48 (p < 0.001) was achieved for the index reliability analyses. Intraclass correlation (ICC) values for the seven most commonly mentioned areas of life affected by the amputation and its treatment ranged from 0.40 to 0.92. Comparing the PGI with the SF-12 Health Survey physical and mental component summaries gave Pearson's correlation coefficients of 0.12 (p < 0.5) and 0.56 (p < 0.001) respectively. Multiple linear regression analysis showed the SF-12 physical and mental component scores explained 31.5% of the variability in PGI scores, however, the mental component scores alone explained 31.2%. Conclusions: The PGI was adapted and found to be moderately reliable in terms of repeatability during successive follow-up interviews. Testing its construct validity supported a stronger relationship between mental health and quality of life than between physical health and quality of life.