Development and psychometric analysis of a Lipid-Lowering Therapy Quality of Life Scale for patients with hypercholesterolemia

Background. Traditional medical evaluation of the outcomes of lipid-lowering therapy have included serum lipid profile assessments and disease-free survival. Clinicians and researchers have come to realize that these traditional outcomes are often inadequate in assessing the impact of hypercholesterolemia and its treatment. Health-related quality of life (HRQOL) assessment has become an important measure of outcome. There currently is no therapy-specific instrument to measure the HRQOL of patients on lipid-lowering therapies for the treatment of hypercholesterolemia.;Methods. Item statements for the Lipid-Lowering Therapy Quality of Life (LLT-QOL) Scale were developed utilizing a qualitative approach with face-to-face patient interviews. A field test and two expert panel reviews further refined the items. The LLT-QOL Scale, the Social Desirability Index, and the Medical Outcomes Short Form 36 (SF-36) were mailed to a random sample of 900 patients with hypercholesterolemia. Principle-components factor analysis, item-total scale and subscale correlations, and coefficient alpha reliability estimates were computed for the new scale as well as for the SF-36. A homotrait-homomethod matrix was computed to examine the construct validity of the two scales.;Results. A total of 455 surveys (51% response rate) were returned and analyzed. The Lipid-Lowering Therapy Quality of Life Instrument assesses HRQOL of patients for two important domains of treatment: (1) pharmacologic and (2) non-pharmacologic. This instrument is composed of 32 items in two subscales. The alpha reliability coefficients were .89 for the total scale and .89 and. 81 for the two subscales respectively. The average inter-item correlation was .48. Validity coefficients between the scales were reviewed for percentages of explained and unexplained variances.;Conclusions. This is the first therapy-specific instrument developed and psychometrically tested to assess HRQOL for hypercholesterolemia. This study provides preliminary reliability and validity evidence for the LLT-QOL Scale. This instrument should provide a useful, sensitive alternative to available generic instruments to quantify HRQOL outcomes in this high-risk population.