Nonorganic pain drawings are associated with low psychological scores on the preoperative SF-36 questionnaire in patients with chronic low back pain

The Short Form 36 questionnaire (SF-36) measures general health and well-be ing. Within the last 5 years it has been used increasingly to characterise patients in the medical literature. Relatively few studies have used the SF -36 on patients with chronic low back pain undergoing preoperative evaluati on, but results suggest that it may be predictive of surgical outcome. Pain drawings are a routine part of evaluation prior to spinal surgery in sever al centres, since their classification of organic or nonorganic has been sh own in some studies to correlate well with psychological characteristics pr edicting poor outcome. The purpose of the present study was to assess possi ble correlations between nonorganic pain drawings and the psychological sca les in the SF-36. We included 128 patients in the study, all of them referr ed from other hospitals. Previous spinal surgery had been undergone by 25%, and 59% required daily medication because of low back pain. All patients c ompleted pain drawings using predefined symbols These pain drawings were sc ored dichotomously as organic or nonorganic based on a brief description of a typical nonorganic characteristics. Patients also completed the Danish v ersion of the SF-36 questionnaire. Statistical analysis was performed using logistic regression analysis. The pain drawing classification was used as the dependent variable and scores on the eight scales of the SF-36 as indep endent variables. P values of <0.05 were considered significant. The mean s cores of the patient population on all eight scales were significantly lowe r than Danish norms. The only scales that correlated with the presence of n onorganic pain drawings were emotional role (RE) and mental health (MH), bo th measuring psychological health. The odds ratio (OR) of receiving a nonor ganic pain drawing was 22 (95% confidence interval, or CI, 7-65) if the sco res on RE and MH were more than 2 standard deviations (SD) below the Danish norm. This is the first study providing evidence that pain drawing ratings are influenced by the psychological scales of the SF-36. The clinical rele vance of this observation regarding prediction of outcome after spinal surg ery should be assessed in future studies.