Preliminary Validity Study of the Pain Disability Index

The Pain Disability Index was designed to measure the extent to which chronic pain interferes with a person's ability to engage in various life activities (Pollard, 1981). For each of seven categories of life activity (Family/Home Responsibility, Recreation, Social Activity, Occupation, Sexual Behavior, Selfcare, and Life Support Activity), patients are asked to rate their level of disability on a graphic rating scale ranging from 0 (-no disability) to 10 (total disability). An over-all disability score is determined by summing the numerical ratings of the seven categories of life activity (range = 0 to 70). The present investigation assessed whether scores on the index could discriminate between two groups of patients with chronic ( 6 mo. or longer) low back pain designated on the basis of external criteria as either highly or minimally disabled. Nine post-surgical patients with low back pain completed the index within 1 wk. after discharge from the hospital; they were designated as the group with high disability. Their scores were compared with those of nine patients classified as low disability; people who reported chronic low back pain but had been working full-time for a minimum of one year and had not sought professional treatment for chronic pain for at least six months. Three women and five men were in each group. The groups were matched by age (range = 22 to 70 yr.). The mean number of years of education was 14.33 (range = 10 to 20 yr.) in the high-disability group and 14.67 (range = 13 to 17 yr.) in the low-disability group. Mean scores on the index for the groups of high and low disability were 48.89 (SD = 14.1; range = 22 to 66) and 16.78 (SD = 10.29; range = 3 to 34), respectively. The obtained 32-point difference between the means of the two groups was statistically significant ( t = 5.52, p < .001) and provides preliminary support for the validity of the index. However, the generalizability of the results of this pilot study cannot be determined until additional research with larger numbers of subjects has been conducted. In addition, further assessment of the ability of this index in making finer distinctions between groups of patients at various levels of disability is needed.