The Self-Perception and Relationships Tool (S-PRT): A novel approach to the measurement of subjective health-related quality of life

BACKGROUND The Self-Perception and Relationships Tool (S-PRT) is intended to be a clinically responsive and holistic assessment of patients' experience of illness and subjective Health Related Quality of Life (HRQL). METHODS A diversity of patients were involved in two phases of this study. Patient samples included individuals involved with renal, cardiology, psychiatric, cancer, chronic pelvic pain, and sleep services. In Phase I, five patient focus groups generated 128 perceptual rating scales. These scales described important characteristics of illness-related experience within six life domains (i.e., Physical, Mental-Emotional, Interpersonal Receptiveness, Interpersonal Contribution, Transpersonal Receptiveness and Transpersonal Orientation). Item reduction was accomplished using Importance Q-sort and Importance Checklist methodologies with 150 patients across the participating services. In Phase II, a refined item pool (88 items) was administered along with measures of health status (SF-36) and spiritual beliefs (Spiritual Involvements and Beliefs Scale--SIBS) to 160 patients, of these 136 patients returned complete response sets. RESULTS Factor analysis of S-PRT results produced a surprisingly clean five-factor solution (Eigen values> 2.0 explaining 73.5% of the pooled variance). Items with weaker or split loadings were removed leaving 36 items to form the final S-PRT rating scales; Intrapersonal Well-being (physical, mental & emotional items), Interpersonal Receptivity, Interpersonal Contribution, Transpersonal Receptivity and Transpersonal Orientation (Eigen values> 5.4 explaining 83.5% of the pooled variance). The internal consistency (Cronbach's Alpha) of these scales was very high (0.82-0.97). Good convergent correlations (0.40 to 0.67) were observed between the S-PRT scales and the Mental Health scales of the SF-36. Correlations between the S-PRT Intrapersonal Well-being scale and three of SF-36 Physical Health scales were moderate (0.30 to 0.46). The criterion-related validity of the S-PRT spiritual scales was supported by moderate convergence (0.40-0.49) with three SIBS scales. CONCLUSION Evidence supports the validity of the S-PRT as a generally applicable measure of perceived health status and HRQL. The test-retest reliability was found to be adequate for most scales, and there is some preliminary evidence that the S-PRT is responsive to patient-reported changes in determinants of their HRQL. Clinical uses and directions for future research are discussed.