Individualized quality of life in patients with low back pain: reliability and validity of the Patient
Generated Index
Sammanfattning
OBJECTIVE: To evaluate the reliability and validity of the improved version of the Patient
Generated Index (PGI) in patients with low back pain.
METHODS: The PGI was administered to 90 patients attending care in 1 of 6 institutions in Norway
and evaluated for reliability and validity. The questionnaire was given out to 61 patients for re-test
purposes.
RESULTS: The PGI was completed correctly by 80 (88.9%) patients and, of the 61 patients responding
to the re-test, 50 (82.0%) completed both surveys correctly. PGI scores were approximately normally
distributed, with a median of 40 (range 80), where 100 is the best possible quality of life. There were
no floor or ceiling effects. The 5 most frequently listed areas affecting quality of life were pain, sleep,
stiffness, socializing and housework. The test-retest intraclass correlation coefficient was 0.73. The
smallest detectable changes for individual and group purposes were 32.8 and 4.6, respectively. The
correlations between PGI scores and other instrument scores followed a priori hypotheses of low to
moderate correlations.
Discussion: The PGI has evidence for reliability and validity in Norwegian patients with low back pain
at the group level and may be considered for application in intervention studies when a
comprehensive evaluation of quality of life is important. However, the smallest detectable change, of
approximately 30 points, may be considered too large for individual purposes in clinical applications.