To assess the validity of the two self-report questionnaires RAPID3 and RADAI5 for measuring the activity of rheumatoid arthritis (RA) in everyday practice, comparatively to the DAS28, CDAI, and SDAI. To determine cutoffs for flare detection based on patients' and physicians' opinions.
The RAPID3 and RADAI5 questionnaires were completed by 200 consecutive patients with RA. The DAS28, CDAI, and SDAI were computed in each patient. Patients and physicians stated whether a flare was occurring. Pairwise Spearman correlation coefficients were computed between the two scores and three indices. The kappa coefficient was used to assess agreement between the patients and physicians regarding the presence of a flare. Receiver-operating characteristic (ROC) curves were constructed to determine cutoffs for flare detection.
The 200 patients had a mean age of 57 ± 11.5 years, a mean RA duration of 13 ± 8.3 years, a mean DAS28 of 3.61 ± 1.43, a mean CDAI of 12.7 ± 9.89, and a mean SDAI of 13.4 ± 10.45. The mean RAPID3 and RADAI5 scores were 3.45 ± 2 and 3.93 ± 2.18, respectively. The RAPID3 and RADAI5 scores correlated significantly with the three composite activity indices, with ρ values ranging from 0.64 to 0.74. The flare rate was 35% according to the patients and 22% according to the physicians, with moderate agreement between patients and physicians (κ=0.44). Flare cutoffs with satisfactory sensitivity and specificity values were obtained for the two scores and three indices. For the three indices, flare cutoffs according to the physicians were within the range indicating moderate disease activity: 4.04 for the DAS28, 14.5 for the CDAI, and 16.7 for the SDAI. The RAPID3 and RADAI5 flare cutoffs according to the physicians and patients were similar, 4.27 and 4.33 for RAPID3 and 4.5 and 4.7 for RADAI5, respectively.
These results confirm the validity of the RAPID3 and RADAI5 self-report questionnaires and support their widespread use in everyday practice in patients with RA. The self-report questionnaire scores correlate with the composite activity index values and allow the detection of activity peaks or flares.