4 Questions About the DACTOS Score for Dactylitis in Psoriatic Arthritis

Dactylitis is a hallmark of psoriatic arthritis (PsA). To better detect inflammation of anatomical structures in the fingers and to monitor the effects of therapy, a group of researchers developed a new scoring system. Lead researcher Alen Zabotti, MD, who is a consultant rheumatologist working in the Unit of Clinical Rheumatology at University Hospital in Udine, Italy, answered our questions about the DACTylitis glObal Sonographic (DACTOS) score¹ that he and his colleagues created.

RHEUMATOLOGY & ARTHRITIS LEARNING NETWORK: What was the motivation behind this project to develop a scoring system specifically for dactylitis in patients with PsA?

Alen Zabotti: Dactylitis is one of the most typical features of PsA, with a high lifetime prevalence,²  a high impact on quality of life, and a greater degree of radiological damage.³ All the composite indices for the evaluation of disease activity and treatment response in patients with PsA include dactylitis. The development of a new imaging score for dactylitis could be useful for the evaluation of the response to treatment, both in trials and in daily clinical practice. DACTOS could be applied in doubtful cases of dactylitis, particularly when disease is less extensive or is not clearly dactylitis (eg, patients with high body mass index).

RALN: Your article reporting on the DACTOS project stated that one of your key objectives was to “identify the characteristic lesions in PsA dactylitis of the hands,” and notes that your group of 12 rheumatologists identified “sonographic elementary lesions” that characterize dactylitis. Can you describe these lesions and their effects on patients with PsA?

AZ: The identification of the characteristic lesions of PsA dactylitis has been the essential step for the subsequent development of the DACTOS score. The sonographic lesions were identified through a systematic literature review and through 3 Delphi rounds among 12 Italian rheumatologists with expertise in the management of PsA and in musculoskeletal ultrasonography. The score includes the evaluation and the grading in B-mode and Power Doppler of synovitis, flexor tenosynovitis, peritendon extensor inflammation, and soft tissue edema. DACTOS score summation ranges from 0 to 25 points.

RALN: You also performed “a web-based and a patient-based intra-rater and inter-rater reliability exercise” as part of your project. What was the purpose of this exercise, and what did it reveal?

AZ: When you propose a new outcome measure instrument, as in the case of the DACTOS score, reliability is a property that you should measure. In the reliability exercise during the development of the DACTOS score, the results analysis showed that the intra-rater reliability of the DACTOS score ranged from good to excellent, while the inter-rater reliability was moderate to good. Overall, the patient-based reliability exercise supported and reinforced the results obtained from the web-based exercise and may serve as guide for future studies. Of note, as  mentioned before, the participants in the reliability exercise are experts in the field of ultrasonography; therefore, these results need to be tested.

RALN: Can rheumatologists make use of the DACTOS score today in their practice, for assessing dactylitis in their patients? Is more research required before it can be applied in daily practice?

AZ: I think that the DACTOS score could assist rheumatologists in their clinical practice. We produced the score to evaluate both the severity of the pathology and the response to treatments in clinical trial and clinical practice settings. A key feature of the DACTOS score is the composite scoring of each lesion. In addition to the global score, the therapeutic response of each lesion characterizing PsA dactylitis could be tracked over time, and this aspect could be useful to differentiate the degrees of response to different treatment. The next step will be to validate this global score for dactylitis against relevant measures of disease activity in a clinical setting.

References:

1. Zabotti A, Sakellariou G, Tinazzi I, et al. Novel and reliable DACTylitis glObal Sonographic (DACTOS) score in psoriatic arthritis. Ann Rheum Dis. 2020;79(8):1037-1043. https://dx.doi.org/10.1136/annrheumdis-2020-217191
2. McGonagle D, Tan AL, Watad A, Helliwell P. Pathophysiology, assessment and treatment of psoriatic dactylitis. Nat Rev Rheumatol 2019;15(2): 113–122. DOI: 10.1038/s41584-018-0147-9
3. Bakewell CJ, Olivieri I, Aydin SZ. Ultrasound and magnetic resonance imaging in the evaluation of psoriatic dactylitis: status and perspectives. J. Rheumatol. 2013; 40(2): 1951–1957. DOI: https://doi.org/10.3899/jrheum.130643