Psoriatic arthritis (PsA) is a chronic inflammatory disease involving skin, peripheral joints, entheses, and axial skeleton. The disease is frequently associated with extrarticular manifestations (EAMs) and comorbidities. In order to create a protocol for PsA diagnosis and global assessment of patients with an algorithm based on anamnestic, clinical, laboratory and imaging procedures, we established a DElphi study on a national scale, named Italian DElphi in psoriatic Arthritis (IDEA). After a literature search, a Delphi poll, involving 52 rheumatologists, was performed. On the basis of the literature search, 202 potential items were identified. The steering committee planned at least two Delphi rounds. In the first Delphi round, the experts judged each of the 202 items using a score ranging from 1 to 9 based on its increasing clinical relevance. The questions posed to experts were How relevant is this procedure/observation/sign/symptom for assessment of a psoriatic arthritis patient? Proposals of additional items, not included in the questionnaire, were also encouraged. The results of the poll were discussed by the Steering Committee, which evaluated the necessity for removing selected procedures or adding additional ones, according to criteria of clinical appropriateness and sustainability. A total of 43 recommended diagnosis and assessment procedures, recognized as items, were derived by combination of the Delphi survey and two National Expert Meetings, and grouped in different areas. Favourable opinion was reached in 100% of cases for several aspects covering the following areas: medical (familial and personal) history, physical evaluation, imaging tool, second level laboratory tests, disease activity measurement and extrarticular manifestations. After performing PsA diagnosis, identification of specific disease activity scores and clinimetric approaches were suggested for assessing the different clinical subsets. Further, results showed the need for investigation on the presence of several EAMs and risk factors. In the context of any area, a rank was assigned for each item by Expert Committee members, in order to create the logical sequence of the algorithm. The final list of recommended diagnosis and assessment procedures, by the Delphi survey and the two National Expert Meetings, was also reported as an algorithm. This study shows results obtained by the combination of a DElphi survey of a group of Italian rheumatologists and two National Expert Meetings, created with the aim of establishing a clinical procedure and algorithm for the diagnosis and the assessment of PsA patients. In order to find accurate and practical diagnostic and assessment items in clinical practice, we have focused our attention on evaluating the different PsA domains. Hence, we conceived the IDEA algorithm in order to address PsA diagnosis and assessment in the context of daily clinical practice. The IDEA algorithm might eventually lead to a multidimensional approach and could represent a useful and practical tool for addressing diagnosis and for assessing the disease appropriately. However, the elaborated algorithm needs to be further investigated in daily practice, for evidencing and proving its eventual efficacy in detecting and staging PsA and its heterogeneous spectrum appropriately.