QWhat are the differences between the ACR20 score and MDA score in regard to psoriatic arthritis?

A
Rachel Printy, PA-C

Rachel Printy, PA-C

PA-C

Medically reviewed on 10.30.24 by Mark Lebwohl, MD

Many of the biologics we prescribe our patients are also approved for psoriatic arthritis. When my moderate to severe PsO patient also appears to have joint disease, I choose a biologic that addresses both their skin and their joints in addition to referring them to rheumatology. The biologics approved for psoriatic arthritis will usually have either ACR20, ACR50, ACR70 or MDA clinical trial data available, so it’s important we understand the criteria for these scores.

The ACR20 is a composite measure defined as an improvement of 20% in the number of tender and swollen joints and a 20% improvement in three of the following five criteria: patient global assessment, physician global assessment, functional ability measure (most often the Health Assessment Questionnaire is used), visual analog pain scale, and acute phase reactant (either erythrocyte sedimentation rate or C-reactive protein). The ACR50 would mean a 50% improvement in these things and ACR70 a 70% improvement.

The Health Assessment Questionnaire (HAQ), developed in 1979, is one of the original measurements of quality of life in patients with rheumatoid arthritis, but has also been validated for use in patients with psoriatic arthritis. There are 8 sections regarding disability with dressing, arising, eating, walking, hygiene, reach, grip, and activities.

The visual analog scale (VAS) for pain is a 100-millimeter straight line with one end meaning no pain and the other end meaning the worst pain imaginable. A patient marks a point on the line that matches the amount of pain he or she feels.

Minimal disease activity is also sometimes used in clinical trials as a treatment target. A patient achieves MDA when 5 of the following 7 criteria are met: tender joint count ≤ 1; swollen joint count ≤ 1; Psoriasis Area and Severity Index (PASI) ≤ 1 or body surface area (BSA) ≤ 3%; patient pain visual analog score (VAS) ≤ 15; patient global disease activity VAS ≤ 20; Health Assessment Questionnaire (HAQ) Disability Index ≤ 0.5; tender entheseal points ≤ 1.

References:

  1. Gossec L, Behrens, F. Minimal Disease Activity as a Treatment Target in Psoriatic Arthritis: A Review of the Literature. The Journal of Rheumatology. January 2018, 45 (1) 6-13; DOI: https://doi.org/10.3899/jrheum.170449
  2. Gonzalez J, Gottlieb A. Review of the Health Assessment Questionnaire Use in Psoriatic Arthritis. Journal of Psoriasis and Psoriatic Arthritis. 2016;1(2):74-79. doi:10.1177/247553031600100205
  3. Fries JF, Spitz P, Kraines RG, Holman HR. Measurement of patient outcome in arthritis. Arthritis Rheum. 1980 Feb;23(2):137-45. doi: 10.1002/art.1780230202
  4. Felson DT, Anderson JJ, Boers M, Bombardier C, Chernoff M, Fried B, Furst D, Goldsmith C, Kieszak S, Lightfoot R, et al. The American College of Rheumatology preliminary core set of disease activity measures for rheumatoid arthritis clinical trials. The Committee on Outcome Measures in Rheumatoid Arthritis Clinical Trials. Arthritis Rheum. 1993 Jun;36(6):729-40