Disease-specific Questionnaire for Quality of Life in Patients with Peripheral Arterial Occlusive Disease in the Stage of Critical Ischemia (FLeQKI)--methodical development of a specific measuring instrument and psychometric evaluation of its validity and reliability (Part 1)

To develop a disease-specific measuring instrument for quality of life in German-speaking patients with peripheral arterial occlusive disease in the stage of critical ischemia and to test it in a prospective study for validity and reliability. We developed a questionnaire compiling items representing subjective disease relevant health states. With 35 of these items, we designed the scales comorbidity (KO), physical pain (SZ), physical functioning (KF), physical state (KS), social functioning (SB), mental health (PB), and therapy-induced limitations (TE). Each item was to be valued as never, seldom, often or always. The scales were standardized with a control group of 40 individuals without peripheral arterial occlusive disease who were interviewed twice in an interval of 6 months using both the FLeQKI and the Medical Outcomes Study Group Short Form 36 (SF-36). Convergent and discriminative validity was determined in 65 consecutive in-patients with peripheral occlusive arterial disease in the stage of critical ischemia who were interviewed with FLeQKI and SF-36 prior to percutaneous transluminal angioplasty (PTA) or bypass operation and 1 month and 6 months after. The internal consistency and test-retest reliability of the FLeQKI were determined in the control group. For statistical analysis, Cronbach's alpha Test and Pearsons Product Moment Correlation were used. The control group consisted of 21 men and 19 women with an age of 73.4+/-7.8, and the treatment group was comprised of 35 men and 30 women with an age of 75.1+/-7.0. In the treatment group, convergent validity reached high values in the scales SB, KF, PB, and SZ (r=0.41-0.70). With their discriminative validity (r=-0.04-0.30), TE and KS were independent, specific dimensions of life quality. The control group showed good values for internal consistency (Cronbach's alpha=0.54-0.93) and for test-retest reliability (r=0.44-0.96). The FLeQKI is well suited for determining the specific impairments of life quality in patients with peripheral arterial occlusive disease at the stage of critical ischemia. Its psychometric scores for validity and reliability corresponded to those of the SF-36.