Prediction of pain center treatment outcome for geriatric chronic pain patients.

Abstract

Geriatric chronic pain patients (age 65 and over) form an increasing percentage of the pain center treatment population. It is therefore important to be able to predict pain center treatment success or failure for these patients; this is the first study to address this concern. Chronic pain patients rated themselves at pain center admission and discharge on 43 rating scales for the areas of pain, functional status, behavioral variables, and other pain center modification categories. The 43 scores at admission were used as potential predictors, while the 43 change scores (from admission to discharge) were the outcome measures to be predicted. Additional possible predictors were 16 other variables that are considered prognostic of treatment outcome, including age, number of surgeries, and prior occupational level. The statistical analysis consisted of a five-step procedure: (a) mathematical techniques were used to remove redundant outcome measures; (b) each of the remaining outcome variables was correlated with the full set of predictor variables; (c) regression techniques were used to predict the outcome variables; (d) these outcome variables were combined into independent factors using factor analysis; and (e) regression techniques were used to predict the factors. The variable-reduction technique was successful in removing 26 of the 43 outcome variables. Factor analysis of change scores of the remaining variables resulted in four factors, which were identified as change in activity, change in pain and behavior, change in constant pain, and change in attitude to pain center goals. The analysis showed that the best predictor of a variable's change score was the initial level of that variable. Regression analysis, using all variables as predictors except initial level, found a number of statistically significant predictors. However, no predictor variable, alone or in combination, was able to account for > 30% of the variance of any outcome measure. These results indicate that we cannot as yet predict geriatric pain center treatment outcome. Potential reasons for these results are discussed.