Specialized Dermatological - Rheumatological Patient Management Improves Diagnostic Outcome and Patient Journey: A Four-Year Analysis

Background: Management of psoriatic arthritis (PsA) and other rheumatological diseases requires an interdisciplinary approach involving dermatologists and rheumatologists. The aim of the study was to analyze the specialized dermatological-rheumatological management before and after foundation of a PsA center. Methods: A retrospective cohort study of all dermatology-rheumatology consultations during two periods was conducted. Period one, from April 1 st , 2016 to February 28 th , 2018 versus period two, from March 1 st , 2018 to January 31 st , 2020, after foundation of a PsA center. Clinical data on patient characteristics including psoriasis subtypes, clinical symptoms and signs, disease activity scores, classication criteria and comorbidities as well as patient journey were extracted and analyzed. Results: 404 consultations were studied. Close collaboration in a PsA center lead to a relevantly shortened patient journey concerning rheumatological complaints: period 1: median (IQR): 36.0 (10.0-126.0) months, period 2: median (IQR): 24.0 (6.0-60.0) months. Established scores and classication criteria such as GEPARD or CASPAR did not assist in diagnosis of PsA. Arthralgia (p=0.0407), swollen joints (p=0.0151), morning stiffness (p=0.0451) and dactylitis (p=0.0086) helped to distinguish between osteoarthritis and PsA. Conclusions:

to 30% of patients (9). Furthermore, patients complain commonly about rheumatological symptoms like arthralgia, which might be hard to differentiate for the dermatologist.
Despite the assumed high importance of interdisciplinary collaboration in dermatology-rheumatology, the clear evidence for it has not been explored signi cantly yet. Therefore, we designed a study at our University Hospital Bonn to compare two speci c periods, one before and one after the foundation of a specialized PsA center, enabling close dermatology-rheumatology cooperation. This is the rst study focusing on the role of early dermatology-rheumatology management for diagnosis and therapy of PsA and other rheumatic diseases considering the patient journey in order to reduce the time for diagnosis in a specialized center setting.

Study design and participants:
We performed a retrospective cohort study of the interdisciplinary dermatology-rheumatology cooperation and management focusing on PsA, other rheumatic diseases and non-rheumatic diseases by comparing two speci c periods: period 1, from April 1st, 2016 to February 28th, 2018 versus period 2, March 1st, 2018 to January 31st, 2020, after foundation of a specialized PsA center. Once a week a consultation shared by dermatologist and rheumatologist took place in the department of rheumatology, with examination of dermatological patients suspected of suffering from rheumatological diseases.

Data collection:
Detailed clinical data was obtained from Dedalus ORBIS™, which is used as main electronic health record system at the University Hospital Bonn. We analyzed all consultation records between both departments. The study followed the principles of the Declaration of Helsinki and the guidelines of Good Clinical General characteristics collected during the study included patient's age, sex, body mass index, comorbidities, history of smoking and laboratory parameters such as rheumatoid factor, anti-CCP antibodies, C-reactive protein and more. Furthermore, we assessed subtype of psoriasis, family history, nail, scalp and rima ani involvement. We also included the following established disease scores: PASI (Psoriasis Area and Severity Index), DLQI (Dermatology Life Quality Index), GEPARD (German Psoriatic Arthritis Diagnostic Questionnaire) and CASPAR (Classi cation Criteria for Psoriatic Arthritis). Other collected data included duration of skin lesions and rheumatological complaints, suspected diagnosis and duration from consult request until consultation. We also assessed all pre-diagnosed and rst diagnosed diseases, clinical signs and symptoms and ful llment of classi cation criteria. CASPAR Page 4/17 classi cation criteria were applied for PsA and respective classi cation criteria for other rheumatological diseases, if available for the diagnosis.

Statistical analysis:
Exploratory data analysis was performed with "R", version 4.0.2 (10). Categorical variables were expressed as absolute and relative frequencies, continuous variables in mean ± standard deviation (SD) and median + interquartile range (IQR). Categorical variables were examined using Chi-Square test or Fisher's exact test, when absolute frequencies were below ve. Continuous variables were compared by using Wilcoxon tests when normality could not be assumed. Descriptive statistics are presented, as p < 0.05 was considered signi cant. For some parameters subgroup analyses were performed based on the presence of psoriasis, PsA, other rheumatological diseases or non-rheumatological diseases including osteoarthritis (OA).

Results
Over the four-year period, 404 dermatological consultations were answered by the department of rheumatology. 61 out of 587 rheumatological consultations were addressed in the rst period and 343 out of 1104 rheumatological consultations in the second period. Excluding follow-up consultations, 373 patients including 165 men and 208 women with a mean age of 52.3 (± 15.4) years were studied. Coexisting diseases were counted separately.
Patient characteristics: Disease activity scores and classi cation criteria: DLQI (mean ± SD) 14.5 (± 6.8) 15.9 (± 6.8) CASPAR (mean ± SD) 5. Psoriasis subtypes: The most prevalent type of psoriasis in patients with PsA was plaque psoriasis reported in up to 86.4% of patients. Concomitant nail, scalp and rima ani involvement was observed with similar frequencies in psoriasis and PsA groups (Table 3). Of all measurements of PsA patients (103), 69 patients (66.99%) reported suffering from skin manifestations before joint complaints appeared, 7 patients (6.80%) stated joint complaints before developing psoriatic skin lesions and 8 patients (7.77%) developed skin and joint complaints simultaneously. 19 patients were not assessed.
Comorbidities: Other-rheumatological diseases: In total, rheumatological diseases other than PsA were observed in 43 patients. The most common diagnoses were connective tissue diseases (20 patients), rheumatoid arthritis (12 patients Symptoms and signs of psoriatic arthritis and osteoarthritis: Patient journey before and after the foundation of a psoriatic arthritis center: A number of 372 consultations were assessed over both periods, 52 in period 1 (14 %) and 320 in period 2 (86 %). Despite the fact that 6-fold increase in consultation was reported in period 2, the distribution of consultation type (day patient vs. inpatient vs. outpatient) was altered. The outpatient clinic played the greatest role in period 2 (139 consultations, 43 %) while it played the subordinated role in period 1 (7 consultations, 13 %).
During this period, 103 patients were diagnosed with PsA in total, out of which 15 were consulted in period 1, while 88 in period 2. These patients suffered from rheumatological complaints for 36 (IQR:10-108) median months in total, 36.0 (IQR:10.0-126.0) median months in period 1 and 24.0 (IQR:6.0-60.0) median months in period 2. No signi cant difference was observed (p = 0.1527) using the Wilcoxon test but a trend for shortened duration of about 12 months was noted making it clinically relevant (Fig. 1).
Period 1: prior foundation of psoriatic arthritis center, period 2: after foundation of psoriatic arthritis center, duration of rheumatological complaints in moths until presentation at the Department of Dermatology, days to rheumatological consultation, assessed median/mean differences, respective diagnoses made.
Overall During both periods, in 78 out of 277 cases, suspected PsA was con rmed and diagnosis was revised in 73 cases, rheumatological disease was revised in eight cases and non-rheumatological disease was diagnosed in 48 cases. The remaining 70 cases persisted as suspected diagnoses. In period 1, PsA was diagnosed in 10 out of 32 patients (31.25%) with suspected PsA, and in period 2, 68 out of 245 patients (27.8%) with suspected PsA were diagnosed with PsA.
In period 1, one of two patients who was rst diagnosed with PsA ful lled the CASPAR classi cation criteria whereas in period 2 all 41 PsA patients ful lled respective classi cation criteria. Concerning rst diagnosis of other rheumatological diseases, in period 1, 1 patient (10%) ful lled the classi cation criteria for rheumatoid arthritis (11). In period 2, 22 patients (95.65%) met the respective criteria. Using the Chi-Square Test for meeting PsA classi cation criteria (p = 0.03458) and the Fishers-Exact-Test for meeting classi cation criteria for other rheumatological diseases (p = 0.0001) over both periods, signi cant differences were observed.

Discussion
To date, very few studies have evaluated the feasibility of setting up a specialized PsA center. In fact, this kind of structure with very close cooperation of dermatologists and rheumatologists is limited mostly to university hospitals. The aim of our PsA center is to optimize the medical care with a team-oriented approach, not only focusing on PsA, but also other rheumatological diseases, which might present with skin abnormalities.
The direct referral of patients with suspected PsA or other rheumatological diseases to the PsA center can help to overcome the confusion between arthritis diagnosis and treatment in patients, thus increasing the attention of patients to management and follow-up in this specialized center. The PsA center's most critical priorities are the early diagnosis and treatment of PsA and other rheumatological diseases. PsA, if left untreated, can result in irreversible joint deformity causing immobility and worsening the overall wellbeing issues (12).
Differential diagnosis is sometimes complex and early management is di cult, requiring the aid of a rheumatologist. There are many studies underlying the delay in diagnosis and treatment of PsA, which typically leads to different orthopedic operations until these patients nally are diagnosed (12,13).
Previous studies also suggested, that there are signi cant deviations in clinical management and followup of patients with psoriasis and PsA, depending on the specialist they initially choose to see, often leading to misdiagnosis and sometimes loss of diagnosis, decreasing the compliance of the patient (14-16). In addition, in a specialized PsA center, rheumatologists are acquainted with topical therapies used in dermatology as well as with the dermatological view of systemic therapies concerning the e cacy in plaque psoriasis. In the PsA center, severity of skin changes are carefully assessed by the dermatologist and reported to the rheumatologist, so that both can decide on a common therapeutic algorithm, tailored for each patient. Furthermore, we can learn more about paradoxical reactions on the skin due to different biological therapies, which could be addressed in an interdisciplinary setting.
In this study, psoriasis and PsA were the most commonly observed diseases. A positive family history for psoriasis was present in 37.86% of patients with PsA. Although, patients with PsA are usually negative for rheumatoid factor, elevated levels were found in 6 cases (5.83%) (17). A similar percentage was observed in patients with psoriasis and non-rheumatological disorders, probably relating to similar presence in the general population (18).
Our data did not show signi cant differences in PASI, DLQI, GEPARD and CASPAR scores between patients with psoriasis (without PsA) and PsA. The GEPARD questionnaire (mean ± SD: Psoriasis = 6.7 (± 3.3), PsA = 8.2 (± 2.7)) and the CASPAR classi cation criteria (mean ± SD: Psoriasis = 5.1 (± 1.8), PsA = 5.8 (± 1.7)) which are commonly used, were not found to be helpful for differentiating between psoriasis and PsA. This is commonly observed in clinical practice, although the literature suggests a better diagnostic yield (19,20). Despite this, the higher level of DLQI in patients with PsA, which primarily affects the impact of the skin symptoms on health-related quality of life, indicated a greater degree of impairment in those patients (21). On the other hand, the dermatologist should not stop asking for joint complaints in psoriasis patients as PsA is often developed in the later history of psoriasis (4).
Plaques psoriasis (86.41%) was the most common type of psoriasis in PsA patients. Current literature underlines our observation, as a 2-3-fold higher risk of developing PsA in patients with scalp lesions, nail dystrophy and perianal lesions is described (22). Our patients with PsA reported scalp involvement in 49.51%, rima ani involvement in 48.54% and nail involvement in 42.72%, so no speci c form of psoriasis was found to be linked to PsA.
Our study yielded a similar increase in prevalence of comorbidities as published, highlighting cardiovascular diseases, gastrointestinal, psychiatric and neurological diseases in psoriasis and PsA (23).
A total of 43 patients out of 373 (11.5%) were diagnosed with another rheumatological disease than PsA, underlining the signi cance of the dermatological-rheumatological approach not only in PsA.
Non-rheumatological diseases were diagnosed in 67 patients out of 373 (18%). In 57 patients osteoarthritis (OA) was diagnosed. Osteoarthritis was diagnosed in 43 patients with initially suspicion of PsA. This underlines the complexity of differentiating OA from PsA for dermatologist. Although, we assessed signi cant differences in the history of arthralgia (p:0.0407), swollen joints (p:0.0151), morning stiffness of the digits (p:0.0451) and dactylitis (p:0.0086) tender joints and pain insomnia did not play prominent roles. These symptoms and clinical signs can help to distinguish between OA and PsA but further diagnostics is required. This emphasizes the di culty for dermatologists in interpreting joint complaints and that is not described in the literature. Future trials will need to focus more on diagnostic tools such as ultrasound, facilitating the diagnosis of arthritis. An additional validated questionnaire could be another future vision improving the diagnostic yield, but is obviously quite complex, as shown by our results concerning CASPAR classi cations criteria and the GEPPARD questionnaire.
Data on patient journey in both the periods show that the time taken for diagnosis by the rheumatologist was about 12 months shorter in period 2 compared to period 1, which is clinically signi cant, in order to prevent irreversible damage of the joint.
There are several examples of collaboration between different departments such as uveitis clinics or reproduction and pregnancy clinics in which the patient is seen by various experts for chronic medical complaints (21,24,25). These experiences demonstrate a signi cant diagnostic and therapeutic bene t. Positive aspects of these specialized centers include avoiding excessive laboratory testing, minimizing the number of visits, e cient decision-making and e cient ow of knowledge leading to fastened diagnosis and procedures for patient management.
Dermatologists and rheumatologists mutually are involved in the management of all overlapping disorders as they speci cally focus on their area of expertise. They see the patients in their respective o ces at different times. This form of practice model resulted in the lack of communication and teamwork between specialists (26). Our practice model not only decreased the duration of rheumatological complaints until request in period 2 but also signi cantly reduced the days required from consultation request until the consultation. In period 2, patients were seen in average 9 days earlier by the rheumatologist. Although, not investigated in this trial, it is imaginable, that the interdisciplinary consultation is not as time consuming as the single visits of each physician.
The limitations of the study are in regards to the retrospective and the monocentric study design. Future prospective studies are necessary in order to con rm our observations.
One of the greatest bene ts of the PsA center is also the inspiration for research provided by the collaboration of both dermatologists and rheumatologists.
is, to the best of our knowledge, the rst joint, dual center for both psoriasis, psoriatic arthritis and patients with other rheumatological diseases. Our conclusions complement the ndings of other research groups worldwide. The importance of service delivery in teams is illustrated by our data in the taking control of complicated or complex patients, suffering from more than one disease into account.

Conclusions
The results of our study con rm the importance of a multidisciplinary university dermatologyrheumatology management in a specialized PsA center. Time to rheumatological examination and time to diagnosis was signi cantly decreased. These data form the concept of a model that can enhance medical treatment through close interdisciplinary cooperation, which should be implemented nationally Dermatological-Rheumatological patient journey over both periods