A summary index for the assessment of quality of life in angina pectoris

When exploring the effects of anti-anginal therapy on quality of life (QL), it is essential to use concise, reliable, outcome measures which focus on those aspects of the disease which are affected by the anginal pain, and which are expected to be responsive to medical intervention. Analysis based on a single comprehensive index is preferable to the use of several indexes as it avoids the potential for conflicting inferences from multiple comparisons. In this paper, we describe the development of a QL index which summarizes the three questionnaires used in the North Karelian Quality of Life (KarQuol) study. The summary index (SI) will be used to compare transdermal and oral nitrate therapy in patients with angina pectoris, and represents the first stage in the construction of a disease-specific evaluative index for future trials.