Response to: 'To DAPSA or not to DAPSA? That is not the question' by Schoels et al.

We thank the authors for the interest in our paper and are grateful for the opportunity to respond to the points raised1. We agree that there is a clear distinction between composite measures of psoriatic arthritis such as DAPSA and composite measures of psoriatic disease such as MDA/VLDA and PASDAS. As the Vienna group rightly point out, these measures differ in terms of the components included, but not due to disagreement within the outcome measure community as suggested in the letter. The choice of components for each composite measure was decided using different methodology in the development of each one, thus resulting in different measures. We believe that this variation in scores is one reason for the need to compare such scores in different populations to establish the optimal measure or measures for PsA. Indeed when the DAPSA was originally suggested, it was because the same components used in the DAREA were identified in a principal component analysis (PCA) in PsA. Interestingly in this analysis, the variables tested were taken from the OMERACT PsA domains and therefore DAPSA was not, a priori, designed specifically to be a unidimensional composite measure. The fourth component identified in the PCA was the PASI highlighting the importance of skin in PsA despite the fact that patients had a low baseline mean PASI of only 3.3. Whilst PASI was not included in the DAPSA as the eigenvalue was 0.949 and therefore just under the threshold of 12, it is interesting to imagine how the results may have differed if it were developed in a group with slightly more active skin disease

Ideal target for psoriatic arthritis? Comparison of remission and low disease activity states in a real-life cohort

Background Psoriatic arthritis (PsA) recommendations state that the target of treatment should be remission or Low disease activity (LDA). We used a real life dataset to compare different potential targets. Methods 250 PsA patients considered in an acceptable disease state according to their rheumatologist were included. Targets for remission were the DAPSA and cDAPSA remission (≤4), VLDA and PASDAS ≤ 1.9. LDA targets analyzed were the DAPSA ≤14, clinical cDAPSA ≤13, MDA, adjusted MDA targets: MDAjoints with both TJC and SJC mandated, MDAskin(PASI mandated), MDAjoints&amp;skin; with TJC, SJC and PASI mandated. Results Comparison of the several candidate targets demonstrates that VLDA is achieved by the lowest proportion of patients and includes patients with the lowest residual disease activity compared with the other remission targets. The modified MDA measures are the most stringent targets for low disease activity in terms of residual disease on joints, psoriasis and enthesitis within patients achieving the target. In both remission and LDA, the inclusion of CRP did not show an added value. The exclusion of a skin domain, as in the DAPSA measures, resulted in negligence of skin disease and a negative impact on the QoL in some patients. Conclusions The different remission and LDA targets show us significant overlap between measures but these measures targeting the same definition do differ in terms of allowance of residual disease. Inclusion of laboratory markers seems unnecessary although exclusion of a skin domain may result in psoriasis not being assessed resulting in residual impactful skin disease. </p

Ideal target for psoriatic arthritis? Comparison of remission and low disease activity states in a real-life cohort

Background Psoriatic arthritis (PsA) recommendations state that the target of treatment should be remission or Low disease activity (LDA). We used a real life dataset to compare different potential targets. Methods 250 PsA patients considered in an acceptable disease state according to their rheumatologist were included. Targets for remission were the DAPSA and cDAPSA remission (≤4), VLDA and PASDAS ≤ 1.9. LDA targets analyzed were the DAPSA ≤14, clinical cDAPSA ≤13, MDA, adjusted MDA targets: MDAjoints with both TJC and SJC mandated, MDAskin(PASI mandated), MDAjointsandskin with TJC, SJC and PASI mandated. Results Comparison of the several candidate targets demonstrates that VLDA is achieved by the lowest proportion of patients and includes patients with the lowest residual disease activity compared with the other remission targets. The modified MDA measures are the most stringent targets for low disease activity in terms of residual disease on joints, psoriasis and enthesitis within patients achieving the target. In both remission and LDA, the inclusion of CRP did not show an added value. The exclusion of a skin domain, as in the DAPSA measures, resulted in negligence of skin disease and a negative impact on the QoL in some patients. Conclusions The different remission and LDA targets show us significant overlap between measures but these measures targeting the same definition do differ in terms of allowance of residual disease. Inclusion of laboratory markers seems unnecessary although exclusion of a skin domain may result in psoriasis not being assessed resulting in residual impactful skin disease. </p

Response to: 'To DAPSA or not to DAPSA? That is not the question' by Schoels et al.

We thank the authors for the interest in our paper and are grateful for the opportunity to respond to the points raised1. We agree that there is a clear distinction between composite measures of psoriatic arthritis such as DAPSA and composite measures of psoriatic disease such as MDA/VLDA and PASDAS. As the Vienna group rightly point out, these measures differ in terms of the components included, but not due to disagreement within the outcome measure community as suggested in the letter. The choice of components for each composite measure was decided using different methodology in the development of each one, thus resulting in different measures. We believe that this variation in scores is one reason for the need to compare such scores in different populations to establish the optimal measure or measures for PsA. Indeed when the DAPSA was originally suggested, it was because the same components used in the DAREA were identified in a principal component analysis (PCA) in PsA. Interestingly in this analysis, the variables tested were taken from the OMERACT PsA domains and therefore DAPSA was not, a priori, designed specifically to be a unidimensional composite measure. The fourth component identified in the PCA was the PASI highlighting the importance of skin in PsA despite the fact that patients had a low baseline mean PASI of only 3.3. Whilst PASI was not included in the DAPSA as the eigenvalue was 0.949 and therefore just under the threshold of 12, it is interesting to imagine how the results may have differed if it were developed in a group with slightly more active skin disease