Background Pain is the most limiting symptom of rheumatoid arthritis (RA) from the patients’ perspective . Surprisingly, a psychometric comparison of common single-item scales measuring pain in RA (i.e. the visual analogue scale [VAS], the numerical rating scale [NRS], and the verbal rating scale [VRS]) remains to be performed.
Objectives To investigate convergent validity, retest reliability and responsiveness of the VAS, the NRS, and the VRS in patients with RA. Moreover, to clarify whether these scales reflect differences in the perception of overall pain during and after medical consultation.
Methods Patients were asked to complete the Health Assessment Questionnaire - Disability Index (HAQ-DI) plus additional items in disease activity and joint swelling or tenderness. The VAS, NRS, and VRS were distributed across this questionnaire to distract the patient’s attention from the previous rating on one of the pain scales. Patients were asked to complete this questionnaire three times: Before, immediately after and one week after the medical consultation. Additionally, information on age, sex, disease duration and disease activity at the time of questionnaire completion were recorded. We investigated convergent validity, retest-reliability, and sensitivity to change of the three pain scales and clarified whether patients reported different levels of overall pain rating among the three pain scales.
Results 225 RA-patients (165 female) with a mean age of 57.09 ± 13.24 yrs and an average disease duration of 9.28 ± 8.95yrs agreed to take part in the survey. The average DAS28 at the time of medical consultation was 3.35 ± 1.56. The average HAQ-DI in the three questionnaires was found to be between 0.82 and 0.90 indicating some difficulties in doing daily physical activities during survey participation. Pearson correlation coefficients showed good convergent validity (r=0.83 to 0.91; all p < 0.001) and retest-reliability (r=0.79 to 0.97 for RA-patients maintaining anti-rheumatic treatment at consultation; all p < 0.001) of the pain scales at all time points . In the subgroup of patients undergoing treatment adaptation, the standardized response mean (SRM) of all pain scales indicated low responsiveness (SRM=0.14 to 0.23) when using the one week follow-up. Interestingly, only the VAS reflected lower levels of pain immediately (t(201)=2.48;p=0.014) and one week after medical consultation (t(169)=2.38;p=0.019) when compared to the level of pain before seeing the physician.
Conclusions Our study shows good convergent validity as well as retest reliability of the VAS, the NRS, and the VRS measuring overall pain in RA-patients but does not confirm previous results on the scales’ responsiveness. Although pain is a symptom that is varying in RA-patients from one day to another, only the VAS detected differences in the patients’ perception of pain.
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Disclosure of Interest None Declared