Patient self-assessment of flare in rheumatoid arthritis: criterion and concurrent validity of the Flare instrument.

The French Flare instrument (FI) aims to identify flares in rheumatoid arthritis between consultation. The objective of the present study was to present both concurrent and criterion validity of the Danish version of FI, as compared to DAS28-CRP. The study was a cross-sectional study comparing FI with DAS28-CRP among patients with rheumatoid arthritis (RA) in connection with the same outpatient visit. The study population consisted of 117 prevalent patients diagnosed with RA according to the ACR 1987/2010 criteria. Consecutive patients were included in the study in relation to their outpatient treatment at the Department of Rheumatology, Aarhus University Hospital, Denmark between 01 October 2012 and 31 December 2012. The sensitivity and specificity were 85.4 (95 % CI, 72.2; 93.9) and 50.7 (95 % CI, 38.4; 63.0), respectively. The positive predictive value was 53.6 (95 %CI, 47.0; 60.1) and the negative predictive value 83.9 (95 % CI, 71.7; 91.5). Positive and negative likelihood ratio were 1.73(95 % CI, 1.33; 2.26) and 0.29 (95 % CI, 0.14; 0.59). Tests with high sensitivity and small LR are most useful for ruling out the disease. Hence, our findings indicate that FI works well in ruling out a flare among patients with RA.