Summary of predictors
| Predictor | Hypothesis | Rationale and evidence for predictors | Coding |
| Gender | Total higher percentage of females in the study is associated with larger effect sizes suggesting that female patients report lower health-related quality of life than controls. | Women with musculoskeletal pain report more severe pain, lower quality of life and disability, higher comorbidity levels of psychiatric disorders than men.25 26 | Total percentage of women included in the study. |
| Age | Total older age in years in the study is associated with larger effect sizes suggesting that older patients report lower health-related quality of life than the young ones. | Older patients report more severe pain and disability.27 | Total mean age (in years) in the study. |
| Comorbidity of psychiatric disorders (mood and/or anxiety disorders) | Percentage of patients with comorbid mood and/or anxiety disorders in the study. | Comorbidity of mood and/or anxiety disorders is higher among patients with chronic LBP than controls and is associated with more severe pain and disability and more dysfunctional coping.14 15 | Percentage of patients with comorbid mood and/or anxiety disorders in the study according to any version of the DSM: eg, DSM-IV-TR30 or DSM-5.31 |
DSM, Diagnostic and Statistical Manual of Mental Disorders; LBP, low-back pain.