Rheumatoid arthritis — open research questions¶
Last curated: 2026-08-31. Stable IDs persist across updates; answered questions should be marked resolved rather than renumbered. Tier 1 questions could change practice and are designable now. Tier 2 questions require enabling methods, longer follow-up or stronger causal foundations.
Tier 1 — practice-changing and designable now¶
OQ-1 — Who should receive pharmacologic prevention?¶
ARIAA and APIPPRA/ALTO show that abatacept can reduce or delay progression in enriched high-risk populations, while five-year TREAT EARLIER data suggest that benefit may depend sharply on serologic and absolute-risk strata (Rech 2024, PMID 38364841; Cope 2026, PMID 41576971; Mulligen 2026, PMID 42392130). A multicenter trial should compare calibrated risk thresholds, overtreatment, adverse events and drug-free non-progression.
OQ-2 — How long must a preventive effect persist to count as prevention?¶
Temporary suppression and delayed onset can still be valuable, but they are not immune tolerance. ARIAA used six months of treatment; after one year of APIPPRA abatacept, ALTO found a diminishing 4.9-month arthritis-free-survival difference at four years and no persistent disease-activity or patient-reported-outcome difference (Rech 2024, PMID 38364841; Cope 2026, PMID 41576971). Follow-up should measure cumulative DMARD exposure and lifetime disease burden, not onset alone.
OQ-3 — Can synovial biopsy choose a biologic mechanism prospectively?¶
R4RA proved multicenter biopsy-stratified randomization is feasible, and RNA B-cell signatures were more informative than simple histology (Humby 2021, PMID 33485455; Rivellese 2022, PMID 35589854). The next trial should randomize biomarker-guided versus clinical selection and test utility, cost and biopsy acceptability.
OQ-4 — Which patients can taper without flare?¶
RETRO and TARA show frequent relapse after reduction/withdrawal and no simple universal sequence advantage (Tascilar 2021, PMID 38297524; van Mulligen 2020, PMID 32482645). A biomarker-stratified taper trial should include time to flare, recapture, structural damage and total drug exposure.
OQ-5 — What is the absolute JAK-inhibitor excess risk in low-risk patients?¶
ORAL Surveillance enrolled people aged ≥50 with cardiovascular risk and found tofacitinib noninferiority failure versus TNF inhibitors for MACE and cancer (Ytterberg 2022, PMID 35081280). Large active-comparator analyses should prespecify age, smoking, ASCVD, cancer and VTE strata and report risk differences per 1,000 person-years.
OQ-6 — Is the JAK safety signal molecule-, dose- or class-specific?¶
Trial and registry programs differ, while biochemical selectivity does not map simply to clinical effects (Traves 2021, PMID 33741556; Russell 2023, PMID 37247942). Head-to-head evidence is unlikely; harmonized individual-participant analyses and negative controls are designable.
OQ-7 — Which RA patients should undergo ILD screening HRCT?¶
Age, sex, smoking, serology and genetics enrich risk, but no model has demonstrated that screening improves outcomes (Sullivan 2024, PMID 39320427; Yao 2025, PMID 41299487). A prospective risk-based screening study should measure stage shift, treatment change, radiation, incidental findings and mortality.
OQ-8 — Which treatment best slows progressive RA-ILD?¶
Guideline options are conditional and rituximab/JAK evidence is mostly observational (Saavedra 2025, PMID 39822854; Krishna Boppana 2024, PMID 38933731; Narváez 2024, PMID 39270812). A platform trial stratified by UIP/non-UIP and inflammatory/fibrotic progression is needed.
OQ-9 — When should antifibrotic and immunomodulatory therapy be combined in RA-ILD?¶
RA-ILD can contain inflammatory and fibrotic processes simultaneously, but combination sequencing lacks direct evidence (Kadura 2021, PMID 34168062; Saavedra 2025, PMID 39822854). A factorial or adaptive trial could test lung and joint outcomes together.
OQ-10 — How should difficult-to-treat RA be decomposed before drug switching?¶
A 23-study synthesis estimated EULAR-defined D2T prevalence at 11.7% (95% CI 9.5–14.3), but only 47.1% (33.3–61.4) had persistent inflammatory refractory disease; prevalence fell to 4.3% after ≥3 and 1.6% after ≥4 advanced-therapy failures (Xie 2026, PMID 41188120). A standardized pathway that separates inflammation, damage, nociplastic pain, adherence/access and comorbidity should be compared with usual mechanism cycling.
OQ-11 — Is triple conventional therapy noninferior to immediate biologic escalation in modern target-based care?¶
RACAT found triple therapy noninferior to etanercept–methotrexate for DAS28 change (upper 95% confidence limit 0.41 below a 0.6 margin), while TEAR found a small radiographic advantage for etanercept at two years (O'Dell 2013, PMID 23755969; Moreland 2012, PMID 22508468). A modern pragmatic trial should incorporate rapid methotrexate optimization, biosimilar pricing, speed, radiographs, adverse events, work and cost.
OQ-12 — What is the safest effective glucocorticoid bridge?¶
CareRA suggested faster functional improvement with a step-down bridge, but a 395-person placebo-controlled trial found no one-year radiographic advantage for high-dose bridging and no week-52 activity difference (Verschueren 2015, PMID 25889222; Krause 2022, PMID 35643951). In a 2,222-person Canadian early-RA cohort, glucocorticoid use at 12 months was 47% after early oral exposure versus 26% after parenteral exposure and 8% without early glucocorticoids; route was not randomized, so confounding by indication remains (Fernández-Codina 2026, PMID 42665531). Because infection risk is dose-dependent even at low sustained doses (George 2020, PMID 32956604), a contemporary trial should randomize route and fixed rapid tapers within methotrexate escalation using cumulative exposure and infection as co-primary safety measures.
OQ-13 — Can residual pain be assigned to an actionable mechanism?¶
Symptoms persist despite formal targets and may reflect inflammation, damage, neuropathy, fibromyalgia, sleep or mood (Michaud 2021, PMID 32619340; Buch 2021, PMID 33293696). A mechanism-stratified care trial should require objective inflammation assessment before randomization.
OQ-14 — Which intervention meaningfully reduces RA fatigue?¶
Fatigue is weakly tied to inflammatory activity and strongly linked with pain, sleep, mood, obesity and inactivity (Katz 2017, PMID 28386762; Pope 2020, PMID 32385141). A factorial trial could test activity, sleep and psychological components with a multidimensional fatigue endpoint.
OQ-15 — Does guideline-concordant comorbidity review reduce hard outcomes?¶
RA carries excess mortality, cardiovascular disease, infection and fracture risk (Lee 2024, PMID 38918258; Mehta 2019, PMID 31245055; Jin 2018, PMID 29546507). Cluster-randomize coordinated annual review against usual care and measure admissions, fractures, events and mortality.
Tier 2 — enabling science and longer-horizon questions¶
OQ-16 — Where does tolerance first break?¶
Lung, periodontal and gut mucosa each have mechanistic and associative evidence, but no universal origin (Lucchino 2019, PMID 31295951; Möller 2020, PMID 32582191). Longitudinal multi-mucosal sampling before ACPA emergence is required.
OQ-17 — Are ACPA-positive and ACPA-negative RA convergent endpoints of different diseases?¶
Genetic and synovial differences are reproducible, yet treatment algorithms remain shared (van Heemst 2014, PMID 24813459; Perera 2024, PMID 38727279). Multi-ancestry inception cohorts with tissue and treatment-response data are needed.
OQ-18 — Which autoantibody features are pathogenic rather than predictive?¶
ACPA titer, breadth and glycosylation change before onset, but causal components remain uncertain (Greenblatt 2020, PMID 32205569). Antigen-specific functional studies must connect human trajectories to tissue injury.
OQ-19 — Are fibroblast states stable therapeutic targets?¶
Single-cell data identify lining/sublining programs associated with inflammation and destruction, but causality and temporal stability are unresolved (Schonfeldova 2022, PMID 34559213; Komatsu 2022, PMID 35705856).
OQ-20 — What sustains remission after cytokine blockade?¶
Many patients relapse after withdrawal despite clinical remission (Tascilar 2021, PMID 38297524). Paired tissue before treatment, remission and taper could distinguish immune suppression from restored homeostasis.
OQ-21 — Can a blood multi-omic signature transport across ancestry and treatment contexts?¶
A 278-person longitudinal RA proteome cohort produced onset/activity/response signals, but external utility is unproven (He 2025, PMID 40691443). A 201-person early-RA cohort found that adding TNFA methylation to clinical data increased the methotrexate-remission model AUC from 0.699 to 0.760, but this is not an externally validated treatment-selection test (Dalix 2026, PMID 42664067). Locked models need multinational prospective validation across ancestry and treatment contexts.
OQ-22 — Does the microbiome cause, amplify or merely reflect RA?¶
Case-control signatures are sensitive to diet, geography and DMARD exposure (Möller 2020, PMID 32582191; Qi 2025, PMID 40825448). Pre-treatment longitudinal sampling and perturbation studies are prerequisites.
OQ-23 — Can smoking cessation after ACPA appearance prevent arthritis?¶
Smoking is a strong ACPA-positive risk factor, but cessation-specific prevention effects are not established (Lucchino 2019, PMID 31295951). A randomized cessation-support trial can test biomarker evolution even if arthritis onset requires larger follow-up.
OQ-24 — What explains organ-specific disease in RA?¶
Only subsets develop ILD, vasculitis, scleritis or Felty syndrome despite shared systemic autoimmunity (Kadura 2021, PMID 34168062; Mertz 2023, PMID 37468085; Turk 2021, PMID 32358156). Cross-organ immune atlases should compare tissue clonotypes and stromal programs.
OQ-25 — Can immune reset produce drug-free remission in refractory RA?¶
Six compassionate blinatumomab cases showed rapid improvement, while CAR-T programs are emerging (Bucci 2024, PMID 38671240). Controlled studies must establish durability, infection risk, neurotoxicity and whether tissue pathology is eliminated.
OQ-26 — How much structural repair is biologically possible?¶
Inflammation activates osteoclasts and suppresses osteoblast repair; erosions rarely normalize despite remission (Komatsu 2022, PMID 35705856). Imaging and tissue studies should distinguish arrested damage from true repair.
OQ-27 — Why do validated targets hit a response ceiling?¶
Roughly 40% show poor response to an individual biologic and 5–20% may be refractory across mechanisms (Humby 2021, PMID 33485455; Bhamidipati 2022, PMID 35248489). Explanations include wrong target, drug delivery, tissue redundancy, irreversible damage and outcome misclassification.
OQ-28 — Can trial outcomes represent participation and treatment burden?¶
Patient-reported-outcome literature establishes pain, fatigue and function, but dosing/monitoring/access burden is less standardized (van Tuyl 2016, PMID 27133486). A core treatment-burden set should be co-developed internationally.
OQ-29 — How should global RA burden be measured where primary data are sparse?¶
GBD projects 31.7 million cases by 2050, but modelled estimates depend on sparse inputs and case definitions (GBD 2021 RA Collaborators 2023, PMID 37795020). A GBD 2023 analysis estimated 12.6 million cases across 129 LMICs and a 4.1-fold prevalence difference between upper-middle- and low-income countries, a gradient that may mix true disease frequency with diagnostic capacity and data availability (Wang 2026, PMID 42495527). Validated low-cost case-finding linked to rheumatology review is needed to distinguish burden from ascertainment.
OQ-30 — Does risk-based RA-ILD screening improve outcomes rather than only detection?¶
ACR/CHEST conditionally recommends PFTs and HRCT for at-risk patients, while pooled RA-ILD prevalence is 18.7% with I²=96.4%, showing how strongly ascertainment changes yield (Johnson 2024, PMID 38973714; Wang 2024, PMID 38547537). A randomized or stepped-wedge program should test stage shift, treatment change, radiation/incidental findings, FVC decline, hospitalization and mortality.
OQ-31 — Which part of the nintedanib effect is additive to optimized immunomodulation in progressive RA-ILD?¶
In the 89-person INBUILD RA-ILD subgroup, nintedanib slowed FVC decline by 116.7 mL/year (95% CI 7.4–226.1), but background DMARDs were not assigned and diarrhea occurred in 61.9% (Matteson 2023, PMID 37209188). A factorial platform should separate joint/inflammatory control from antifibrotic effect and measure discontinuation and quality of life.
OQ-32 — Can remote monitoring reduce visits without widening digital inequity?¶
Controlled ePROM studies suggest a small disease-activity benefit (SMD −0.15, 95% CI −0.27 to −0.03), but most were high risk of bias; AEGORA did not improve self-efficacy and retained only 43% of app users at week 16 (Arumalla 2023, PMID 37204273; Doumen 2025, PMID 39576683). A service trial should stratify digital access, literacy and language and test missed flares, visit burden and equity.
OQ-33 — Can vagus-nerve modulation deliver durable benefit with acceptable procedural risk?¶
RESET-RA achieved ACR20 in 35.2% with active versus 24.2% with sham stimulation at three months (p=0.0209), with related serious events confined to the perioperative period, but open-label follow-up cannot establish durability against sham (Tesser 2026, PMID 41429981). A longer blinded comparison should include device revision, infection, patient burden and cost.
OQ-34 — Which preference-sensitive decisions materially improve adherence and outcomes?¶
Across 36 studies, many patients weighted benefit above route or adverse effects, but preference patterns varied and discrete-choice methods were heterogeneous (Durand 2020, PMID 30988125; Zartab 2021, PMID 34447905). A trial of preference-concordant versus standard sequencing should prespecify persistence, disease control, regret and equity.
Dots not yet connected¶
| # | Dot A | Dot B | The missing junction | Powers |
|---|---|---|---|---|
| D-1 | ACPA-positive mucosal autoimmunity | Synovial fibroblast pathotypes | Determine whether specific mucosal trajectories seed specific stromal states | Prevention + tissue precision |
| D-2 | ARIAA/APIPPRA prevention effects | R4RA tissue selectors | Biopsy or less-invasive tissue signatures before arthritis to select prevention mechanism | Prevention + precision trials |
| D-3 | ORAL Surveillance CV harm | Synovial JAK/STAT activity | Test whether high tissue pathway dependence identifies patients with enough benefit to offset risk | Pharmacology + safety |
| D-4 | RA-ILD MUC5B/UIP risk | ACPA maturation in lung | Longitudinal airway/blood sampling before joint and lung phenotypes diverge | Genetics + mucosal immunology + lung |
| D-5 | Clinical remission | Persistent tissue cell states | Paired biopsy during taper to predict flare and drug-free remission | Treat-to-target + single-cell biology |
| D-6 | Severe fatigue | Inflammatory/non-inflammatory D2T phenotypes | Mechanism-based fatigue intervention after objective synovitis classification | Patient outcomes + imaging |
| D-7 | Glucocorticoid infection risk | T2T speed | Test whether faster MTX/biologic optimization reduces cumulative steroid infection without more flare | Strategy + safety |
| D-8 | Periodontal dysbiosis | Prevention cohorts | Randomize periodontal treatment with antibody and arthritis endpoints in calibrated high-risk people | Dentistry + prevention |
| D-9 | Fracture risk | Synovial/bone remodeling signatures | Link local erosion biology to systemic fragility and treatment response | Bone + tissue omics |
| D-10 | Work loss | Drug route and monitoring burden | Pragmatic comparison of clinically equivalent regimens using job retention | Pharmacology + health services |
| D-11 | Cervical instability | Modern deep remission | Establish contemporary incidence and whether sustained control prevents silent progression | Imaging + long-term outcomes |
| D-12 | Patient-organization priorities | Trial endpoint selection | International patient-led core set spanning participation, uncertainty and treatment burden | Advocacy + trial design |
| D-13 | Seronegative preclinical risk | Prevention trials centered on ACPA | Build a validated ACPA-negative enrichment strategy before intervention | Classification + prevention |
| D-14 | Registry pharmacovigilance | Tissue-defined mechanisms | Determine whether biologic pathotypes also predict infection, cancer or CV toxicity | Precision + safety |
| D-15 | Risk-based RA-ILD screening | Progressive-fibrosis treatment | Test whether earlier HRCT detection identifies a stage in which FVC decline is more modifiable | Screening + antifibrotic therapy |
| D-16 | Digital symptom monitoring | Patient–physician discordance | Determine whether discordant pain/fatigue trajectories can trigger mechanism-specific care rather than indiscriminate escalation | Patient outcomes + services |
| D-17 | Prevention-trial recruitment failure | Patient preference science | Co-design risk communication and treatment thresholds that make prevention trials acceptable without coercion | Prevention + behavioral science |
| D-18 | Vagus-nerve modulation | Synovial cell-state atlases | Identify whether neural response maps to macrophage/fibroblast pathotypes and predicts durable benefit | Bioelectronics + tissue biology |