Role of psychological distress screening in predicting the outcomes of epidural steroid injection in chronic low back pain

Abstract

BackgroundThere is a paucity of studies investigating relationship between psychological distress and effectiveness of epidural steroid injection in patients with chronic lower back pain (CLBP). AimsThis prospective cohort study assessed whether the outcome can be predicted in CLBP patients undergoing epidural injection by pre-treatment psychological stress stratification using objective screening methods. Methods96 patients with CLBP were recruited to this prospective cohort study. Preoperative level of psychological distress was measured using Modified Zung Index (MZI) and Modified Somatic Perception Questionnaire (MSPQ); pain with Visual Analogue Score (VAS) and McGill Pain Questionnaire (MPQ) and back pain related disability with Oswestry Disability Index (ODI). Fluoroscopic caudal epidural steroid injection comprising 80 mg methylprednisolone and 8 mg of lignocaine was performed. Scores were repeated at 6, 12, and 26 weeks. Successful outcome was Minimal Clinically Important Change (MCIC) in any given measure. ResultsThere were 60 (62.5%) not-distressed patients, 3(3.1%) purely somatising, 15(15.6%) depressed and 18(18.8%) with mixed distress. Preoperative VAS was 82.4, MPQ 18.2 and ODI 51.6. Average VAS and MPQ improved significantly at 6 and 26 weeks. Average magnitude of change of VAS and ODI did not differ between distressed and not-distressed. MPQ improved significantly more in the distressed. MZI was negatively associated with VAS MCIC at 6 weeks and 6 months but it failed to predict the outcome independently. MSPQ was the only individual predictor of MPQ-MCIC at any time; MSPQ≥8 could predict MPQ-MCIC at 6 months with 53%-sensitivity and 78%-specificity. None of psychological measures used showed a significant predictive value of ODI at any follow-up point ConclusionsPsychological distress may predict response only in certain outcome measures in patients suffering from nonspecific CLBP. If the interest lied primarily in pain and functional improvement, the psychological distress failed to discriminate the results at 6 months.