Background/Purpose: Two groups established cut-off values for Disease Activity Index for Psoriatic Arthritis (DAPSA)^1-2. The clinical DAPSA (cDAPSA) excludes CRP from its calculation and the authors recommend the use of the same cut-off values as DAPSA. To evaluate the concordance between the two cut-off values established for DAPSA and to validate cDAPSA and develop its cut-off values. Methods: Patients ³ 18 years of age with Psoriatic Arthritis (PsA) according to CASPAR criteria belonging to RAPSODIA cohort were included. We recorded clinical data. DAPSA and cDAPSA were calculated. Patients were classified according to both cut-off values. Those patients who showed disagreement in the classification between both cut-off values ​​were re-evaluated by the opinion of four rheumatologists with experience in the evaluation of PsA patients. Results: 119 patients were included, 62 males (52.1%), median age 54 years old (IQR 42-63), median disease duration 8 years (IQR 3-15). 49.6% of patients had pure peripheral involvement and 48.7% had mixed involvement. Median value for DAPSA was 12 (IQR 7-19) and for cDAPSA was 13 (IQR 7-19). Correlation between both DAPSA versions was very good Rho=0,85. Table 1 shows the classification of patients according to our cut-off values and those proposed by Schoels et al. A high agreement between cut-off values of both versions was observed Ƙ: 0.85 (p= 0.0001). Only 7 patients were discordant, and according to expert«s opinion, the performance of Schoels«s DAPSA- cut-off values was better. A lower agreement was observed between DAPSA and clinical DAPSA Ƙ: 0.79 (p = 0.0001), with 10 discordant patients. For this reason, we established new cut-off values ​​for cDAPSA: Remission< 2.5, low disease activity 2.5 to ² 11.5 (AUC: 0.94, Se: 92.6% and Sp: 100%), moderate disease activity >11.5 to ² 23 (AUC: 0.99, Se: 100% and Sp: 96.3%) and high disease activity > 23 (AUC: 0.99, Se: 100% and Sp: 95.5%). These cut-off values showed a better balance in sensitivity and specificity than those previously proposed.  Conclusion: The concordance between the two cut-off values of DAPSA was good, although Schoels«s DAPSA cut-off values showed better discrimination according to expert opinion. The cut-off values for cDAPSA should be reviewed for better sensitivity and specificity.

¹ Schoels MM, Aletaha D, Alasti F, Smolen JS. Ann Rheum Dis 2016;75(5):811-8.

² Gallino Yanzi J, Schneeberger EE, Cerda OL,  Zaffarana C, Landi M, Rosemffet MG, et al. Arthritis Rheum 2015;67(Suppl 10).

Table 1.