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Survey Highlights Inconsistencies in Toe Joint Scoring for PsA 66/68 Count
A recent survey revealed widespread confusion among rheumatologists of what toe joints to count in the 66/68 swollen and tender joint count in psoriatic arthritis (PsA): should you count only the metatarsophalangeal (MTP) and the proximal interphalangeal (PIP) joints, or should you count each MTP joint and count the PIP and distal interphalangeal (DIP) joints as a single joint?1
Investigators, led by Gabriele De Marco, PhD, from NIHR Leeds Biomedical Research Centre at Leeds Teaching Hospitals Trust, Leeds in the UK, were conducting a recent randomized clinical trial that assessed whether the combination of methotrexate and golimumab (GOL) plus steroids (CS) was superior to methotrexate plus steroids in reducing clinical disease activity among participants with PsA.2 However, they ran into an unexpected finding—inconsistency on how to complete a PsA 66/68 count.1 Unlike the 76/78 swollen and tender joint count, which assesses individual joints of the lesser toes, the 66/68 joint counts may not always do this.
This finding sparked the investigators to conduct an international online survey in April 2025 to determine worldwide clinical practice of the PsA 66/68 count. The survey was sent to 1300 members of the Group for Research and Assessment of Psoriatic Arthritis, 90 members of the British Society for Psoriatic Arthritis, and 200 members of the British Society for Spondylarthritis.
De Marco and colleagues stated 2 methods: method A, where rheumatologists only count the MTP joint and PIP joint but disregard the DIP joint, and method B, where rheumatologists count each MTP joint but merge the PIP/DIP joints of each digit as if they were 1 joint. Additionally, with method B, if either or both the PIP or DIP joints are involved, then the site is scored positive.
Although the Outcome Measures in Rheumatology (OMERACT) PsA working group recently recommended using method A, uniformity for PsA 66/68 count does not exist in trials and longitudinal observational studies.
Among 117 respondents, 73% reported being currently active in clinical trial research, and 79% endorsed the use of the 66/69 joint count to assess peripheral joints in PsA.
More than half of the respondents (56%) said that when assessing the joints of the lesser toes, they only count the MTP and PIP joints, disregarding the DIP joint, thus following method A. Still, 33% of respondents used method B, counting the PIP and DIP joints as 1 unit. A quarter of respondents (25%) who followed method B said they received specific training on this method.
Investigators recognized the difficulty of individually distinguishing the PIP and DIP joints in the lesser toes during a clinical examination. It can be especially hard at the fifth toe, where there is often only 1 joint distal to the MTP joint. They also wrote that isolated DIP joint inflammation does occur in PsA, although not commonly.
Several respondents reported confusion with the 66/68 count and requested additional training, such as access to online video material.
“We propose that further consensus is needed on whether it would be more appropriate to adopt the 76/78 joint count in order to capture disease extent in all toe joints, or that a further evaluation of how the toe joints are counted in the 66/68 joint count is needed,” investigators wrote. “We believe it is important to remove confusion and standardize joint count evaluation of the toes in the context of clinical trials.”
References
De Marco G, Marzo-Ortega H, Helliwell PS. How Should We Count the Toe Joints in the 66/68 Joint Count in Psoriatic Arthritis? Results of an International Survey. J Rheumatol. 2025 Apr 15:jrheum.2025-0072. doi: 10.3899/jrheum.2025-0072. Epub ahead of print. PMID: 40233990.
De Marco, G., Hensor, E., Helliwell, P.S. et al.. OP0184 A Treatment Strategy Combining Tnf-Inhibitor, Methotrexate And Steroids Is Not Superior To Methotrexate And Steroids In Early Psoriatic Arthritis: Results From The Golmepsa Randomised, Double-Blind Clinical Trial. Annals of the Rheumatic Diseases. EULAR 2024 European Congress of Rheumatology, 12-15 Jun 2024, Vienna, Austria. https://www.jrheum.org/content/jrheum/early/2025/04/09/jrheum.2025-0072.full.pdf. Accessed April 23, 2025.
