A small rheumatology glossary
Published on: 2025-06-19
TL;DR
This is a glossary of rheumatology and epidemiology terms and definitions that I often forget. This list is always growing and never finished, with the small caveat that I'll certainly forget about it eventually. 🌚🌝A
Arthralgia
Arthralgia is the earliest stage of RA development and features pain with no objective inflammation or joint swelling.
C
Composite disease activity scores
Composite disease activity scores are mathematical devices that integrate several component scores into a single value. The purpose of this integration is for both the patient and clinician to better be able to track the progression of the disease.
Disease Activity Score, 28 joints
→ DAS28
The DAS28 is the most used composite score in RA.
There are two versions which differ in the acute phase reactants used: DAS28CRP and DAS28ESR. The remaining components are identical: 28 tender joint count (→ TJC28), 28 swollen joint count (→ SJC28), and patient-rated global health (→ PGH, 0-100 mm visual analogue scale).
The disease activity score calculation differs depending on which acute phase reactant was used:
Clinical Disease Activity Index
→ CDAI
The CDAI does not require an acute phase reactant and can therefore be calculated right away when the patient visits the clinic.
The component scores are TJC28, SJC28, PGH, and evaluator-rated global health (→ EGH, 0-10 cm visual analogue scale).
To calculate the CDAI score, the clinician simply adds up the component scores.
Simplified Disease Activity Index
→ SDAI
The component scores are TJC28, SJC28, CRP, PGH, and EGH (0-10 cm).
To calculate the SDAI score, the clinician simply adds up the component scores.
Cutoffs
It is common practise to apply cutoffs to composite scores and assign discrete disease states to the resulting categories.
The cutoffs below are those for the most common composite scores used in RA.
| Disease activity | DAS28ESR | DAS28CRP | SDAI | CDAI |
|---|---|---|---|---|
| Remission | < 2.6 | < 2.4 | ≤ 3.3 | ≤ 2.8 |
| Low | ≤ 3.2 | ≤ 2.9 | ≤ 11.0 | ≤ 10.0 |
| Moderate | ≤ 5.1 | ≤ 4.6 | ≤ 26.0 | ≤ 22.0 |
| High | > 5.1 | > 4.6 | > 26.0 | > 22.0 |
D
Disease-modifying antirheumatic drug
→ DMARD
DMARDs are a category of otherwise unrelated disease-modifying drugs grouped due to their use in RA to slow down disease progression. The term DMARD is often used separate these drugs from NSAIDs and steroids.
Conventional synthetic DMARD
→ csDMARD
csDMARDs are the “traditional” drugs used to treat RA, such as methotrexate (→ MTX), sulfasalazine, leflunomide, hydroxychloroquine, and gold salts.
Biologic DMARD
→ bDMARD
bDMARDs are engineered proteins targeting specific inflammatory pathways, blocking cytokines, immune cells, or other receptors that play a key role in autoimmunity. Examples are tumor necrosis factor-alpha inhibitors (→ TNFi) and interleukin (→ IL) inhibitors.
Targeted synthetic DMARD
→ tsDMARD
tsDMARDs are are drugs developed to target specific molecular structures, such as Janus kinase inhibitors (→ JAKi), e.g., baricitinib and tofacitinib.
N
Non-steroidal anti-inflammatory drug
→ NSAID
NSAIDs treat the inflammation present in, e.g., RA, but not its underlying cause.
P
Pain
The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated wit actual or potential tissue damage, or described in terms of such damage”.
There are currently four main groups of pain:
Nociceptive pain
Nociceptive pain relates to tissue damage, and could be the result of, e.g., arthritis or enthesitis.
Neuropathic pain
Neuropathic pain is caused by different forms of damage to the peripheral or central nervous system and often anatomically defined, corresponding to, e.g., a dermatoma after nerve injury.
Nociplastic pain
Nociplastic pain describes pain related to disturbances in the pain regulating systems, which is a prominent feature of fibromyalgia.
Two signs of nociplastic pain include:
- Allodynia: A person with allodynia perceives a stimulus as painful that would not normally be perceived as painful.
- Hyperalgesia: A person with hyperalgesia perceives low-pain stimuli as more painful.
Psychogenic pain
Psychogenic pain is uncommon and only found in connection with severe psychosis.
Prevention
The WHO defines prevention as “approaches and activities aimed at reducing the likelihood that a disease or disorder will affect an individual, interrupting or slowing the progress of the disorder or reducing disability”. 2
Primordial prevention
Primordial prevention targets exposures of population risk factors before they can put anyone at risk.
Primary prevention
Primary prevention targets the first apparent clinical manifestation of the preventable outcome (e.g., a vaccination for a disease).
Secondary prevention
Secondary prevention aims at detecting a preventable outcome during a period in which it has not yet inflicted cricial and permanent damage.
Tertiary prevention
Tertiary prevention aims at reducing the impact of a preventable outcome that already affects an individual negatively.
Quaternary prevention
Quaternary prevention aims to reduce overmedicalisation by identifying those individuals not or no longer in need of treatment.
R
Rheumatoid arthritis
→ RA
Rheumatoid arthritis is a chronic autoimmune disease that affects the joints. Rheumatoid arthritis is commonly abbreviated RA.
Difficult-to-treat RA
→ D2T-RA
D2T-RA describes RA which has been unsuccessfully treated with at least two different mechanism of action b/tsDMARDs and shows signs of active or progressive disease (for more details, see the EULAR definition of D2T-RA 1 ). Progressive disease is not limited to inflammatory joint pathology but captures a wider picture contributing to treatment failure, such as comorbidity, obesity, and fibromyalgia.
More specifically, the EULAR defintion comprises three elements:
- history of failed treatments
- features of active disease
- the perception of challenging RA by the clinician and / or patient
Why at least two different mechanisms?
Two different mechanisms of action failing to control the RA disease reflects a drug-resistant disease state. 3
S
Steroids
Steroids dampen the immune response in autoimmune diseases such as RA but cannot slow down the progression of the disease.
T
Treat to target strategy
→ T2T
T2T aims to reduce disease activity to a specific target rather than treating symptoms as they arise. The treatment target is typically DAS28 remission, or low disease activity (→ LDA) if remission is not a realistic goal.