Psychological factors can cause false pain classification on painDETECT.

Background and aims The painDETECT questionnaire (PD-Q) has been widely used as a screening tool for the identification of neuropathic pain (NeP) as well as a tool for the characterization of patients' pain profile. In contrast to other NeP screening tools, the PD-Q is the only screening tool with weighted sensory descriptors. It is possible that responses to the PD-Q sensory descriptors are influenced by psychological factors, such as catastrophizing or anxiety, which potentially might contribute to an overall higher score of PD-Q and a false positive identification of NeP. This study aimed to explore (i) the relationship between psychological factors (catastrophizing, anxiety, depression and stress) and the total PD-Q score and (ii) if psychological factors are associated with false positive identifications of NeP on the PD-Q compared to clinically diagnosed NeP. Methods The study was a retrospective review of 1,101 patients attending an outpatient pain centre. Patients were asked to complete the PD-Q, the Pain Catastrophizing Scale (PCS), the Depression, Anxiety and Stress Scale (DASS) and the Brief Pain Inventory (BPI). For patients who were identified by PD-Q as having NeP, their medical records were reviewed to establish if they had a clinical diagnosis of NeP. Results Accounting for missing data, complete datasets of 652 patients (mean age 51 (SD14) years, range 18-88; 57% females) were available for analysis. Based on PD-Q scoring, NeP was likely present in 285 (44%) patients. Depression, anxiety, stress, catastrophizing, BPI pain and BPI interference were all significantly related to each other (p < 0.0001) and patients displaying these traits were significantly more likely to have a positive PD-Q score (p < 0.0001). For patients classified by PD-Q as having NeP, only 50% of patients had a clinical diagnosis of NeP. Anxiety was significantly associated with a false positive classification of NeP on PD-Q (p = 0.0036). Conclusions Our retrospective study showed that psychological factors including catastrophizing, depression, anxiety, and stress were all influential in producing a higher score on the PD-Q. We observed a high rate of false positive NeP classification which was associated with the presence of anxiety. Implications Clinicians and researchers should be aware that a patient's psychological state may influence the responses to PD-Q and consequently the final PD-Q score and its NeP classification.