Psychological questionnaires: do "abnormal" scores precede or follow first-time low back pain?

STUDY DESIGN

A prospective study of psychological risk factors for first-time low back pain with repeated use of psychological questionnaires.

OBJECTIVES

To measure the reproducibility of scores from psychological questionnaires, and to compare this with changes that follow an individual's first attack of back pain. Secondly, to determine which scores predict first-time back pain.

SUMMARY OF BACKGROUND DATA

"Abnormal" psychometric scores are associated with several aspects of back pain behavior. Little is known, however, about their reproducibility or long-term stability, and there has been no definitive answer to the question: which comes first, "abnormal" scores or low back pain?

METHODS

403 volunteers with no history of "serious" low back pain (defined as pain requiring medical attention or absence from work) participated in a functional spinal assessment. At the time of initial assessment and at 6-month intervals thereafter, the volunteers completed the following questionnaires: the Health Locus of Control, which was subdivided into three sections labelled "Internal," "Powerful others," and "Chance"; the Modified Somatic Perception Questionnaire; and the Zung depression scale. Scores from the Modified Somatic Perception Questionnaire and from the Zung depression scale were added to form a measure of psychological distress. Additional questionnaires inquired about any back pain experienced in the previous 6 months. Only three volunteers had left the study at the 18-month follow-up. At that time 162 participants had reported "any" low back pain, of which 79 were "serious."

RESULTS

Intraclass correlation coefficients for scores repeated after 6 months ranged from 0.67-0.80, and reproducibility of scores was equally high between the 0-, 6-, 12- and 18-month assessments. None of the scores were affected by "any" low back pain, and only the Modified Somatic Perception Questionnaire scores changed after "serious" back pain was reported. In a multivariate analysis, the most significant predictor of first time "serious" or "any" back pain was a history of non-"serious" back pain (P < 0.001). Of the psychological factors, the sum of Modified Somatic Perception Questionnaire scores and Zung questionnaire scores was the best predictor of "serious" back pain (P = 0.037), and the Modified Somatic Perception Questionnaire score was the best predictor of "any" back pain (P = 0.002). The 25% of participants with the highest sum of scores from the Modified Somatic Perception Questionnaire and Zung questionnaire was 2.7 times more likely to develop "serious" back pain than the 25% with the lowest sum of these scores. Nevertheless, after accounting for the affects of a history of non-"serious" back pain, psychometric scores predicted less than an additional 3% of reported back pain.

CONCLUSIONS

The scores from the Modified Somatic Perception Questionnaire and Zung questionnaire were reproducible over 18 months and were affected little by first episodes of back pain; yet these scores were significant predictors of it. "Abnormal" scores from these questionnaires precede back pain in a small number of people.