Search

Magnetic resonance imaging (MRI) of small joints sensitively detects inflammation. This inflammation, and tenosynovitis in particular, has been shown to predict rheumatoid arthritis (RA) development in arthralgia patients. These data have predominantly been acquired on 1.0–1.5 T MRI. However, 3.0 T is now commonly used in practice. Evidence on the comparability of these field strengths is scarce and has never included subtle inflammation in arthralgia patients or tenosynovitis. Therefore, we assessed the comparability of 1.5 T and 3.0 T in detecting subclinical inflammation in arthralgia patients. A total of 2968 locations (joints, bones, tendon sheaths) in the hands and forefeet of 28 patients with small-joint arthralgia, at risk for RA, were imaged on both 1.5 and 3.0 T MRI. Two blinded readers independently scored erosions, osteitis, synovitis, and tenosynovitis, in line with the Rheumatoid Arthritis Magnetic Resonance Imaging Score (RAMRIS). Features were summed into inflammation (osteitis, synovitis, tenosynovitis) and RAMRIS (inflammation and erosions). Agreement was assessed with intraclass correlation coefficients (ICCs) for continuous scores and after dichotomization into presence or absence of inflammation, on patient and location levels. Interreader ICCs were excellent (> 0.90). Comparing 1.5 and 3.0 T revealed an ICC of 0.90 for inflammation and RAMRIS. ICCs for individual inflammation features were: tenosynovitis 0.87 (95% confidence interval 0.74–0.94), synovitis 0.65 (0.24–0.84), and osteitis 0.96 (0.91–0.98). Agreement was 83% for inflammation and 89% for RAMRIS. Analyses on the location level showed similar results. Agreement on subclinical inflammation between 1.5 T and 3.0 T was excellent. Although synovitis scores were slightly different, synovitis often occurs simultaneously with other inflammatory signs, suggesting that scientific results on the predictive value of MRI-detected inflammation for RA, obtained on 1.5 T MRI, can be generalized to 3.0 T MRI. [ABSTRACT FROM AUTHOR]

Background: Prevention of rheumatoid arthritis has become a definitive target. However, whether prevention of anti-citrullinated protein antibody (ACPA)-negative rheumatoid arthritis is possible is still unknown. We aimed to assess the efficacy of a 1-year course of methotrexate on the development of rheumatoid arthritis in ACPA-negative people with clinically suspect arthralgia and predicted increased risk of rheumatoid arthritis., Methods: For this follow-up analysis, we used 4-year data from the TREAT EARLIER trial, a randomised, double-blind, placebo-controlled, proof-of-concept trial conducted in the southwest region of the Netherlands from which we analysed data collected between April 16, 2015, and Sept 11, 2023. ACPA-positive and ACPA-negative adults aged 18 years or older with arthralgia and subclinical joint inflammation who were at risk of developing rheumatoid arthritis were eligible for enrolment. For TREAT EARLIER, participants were randomly assigned (1:1) to active treatment or placebo. Active treatment consisted of a single intramuscular glucocorticoid injection (120 mg of methylprednisolone) upon inclusion, then a 1-year course of methotrexate. Placebo consisted of a single placebo injection followed by a 1-year course of placebo tablets. Trial visits occurred every 4 months during the first 2 years, at which clinical and questionnaire data were collected. Total follow-up was 4 years. For this analysis, participants were stratified via a prediction model into low risk, increased risk, and high risk of developing persistent, clinically apparent inflammatory arthritis. The primary outcome was development of rheumatoid arthritis, defined as the presence of clinically apparent inflammatory arthritis and clinical diagnosis of rheumatoid arthritis, and was assessed in all TREAT EARLIER participants. Severity of subclinical joint inflammation, physical functioning, and grip strength in ACPA-negative participants was studied in each risk group over a period of 2 years., Findings: 901 people with clinically suspect arthralgia were assessed for eligibility and 236 were enrolled in TREAT EARLIER. All 236 participants were included in the intention-to-treat analysis and 217 (92%) completed 4-year follow-up. 154 (65%) of 236 participants were women and 82 (35%) were men, 182 (77%) were ACPA-negative and 54 (23%) were ACPA-positive. Of the 182 randomly assigned ACPA-negative participants, none were predicted to be at high risk of developing persistent, clinically apparent inflammatory arthritis, 66 (36%) at increased risk, and 116 (64%) at low risk. Of the 54 ACPA-positive participants, 24 (44%) were predicted to be at high risk, 30 (56%) at increased risk, and none at low risk. After 4 years, 52 (22%) of 236 participants had developed the primary outcome of rheumatoid arthritis (25 [21%] of 119 in the treatment group and 27 [23%] of 117 in the placebo group). Of the 66 ACPA-negative participants predicted to be at increased risk, three (9%) of 35 in the treatment group developed the primary outcome compared with nine (29%) of 31 in the placebo group (hazard ratio 0·27, 95% CI 0·07-0·99; p=0·034). Of the 116 ACPA-negative participants predicted to be at low risk, four (8%) of 53 in the treatment group met the primary outcome compared with six (10%) of 63 in the placebo group (0·79, 0·22-2·80; p=0·71). Thus, after risk stratification, a 1-year course of methotrexate was associated with a reduced rate of development of ACPA-negative rheumatoid arthritis in participants with predicted increased risk of developing the disease. Subclinical joint inflammation, physical functioning, and grip strength persistently improved upon treatment in ACPA-negative participants with increased risk of developing rheumatoid arthritis, but not in those with low risk., Interpretation: Risk stratification can be helpful in trials of ACPA-negative people with clinically suspect arthralgia to identify participants who could benefit from treatment to prevent development of rheumatoid arthritis., Funding: Dutch Research Council-ZonMw, Dutch Arthritis Society., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Objectives: ACPA-positive and ACPA-negative RA differ in underlying risk factors but have a similar clinical presentation at RA diagnosis. It is unknown what the ACPA-associated differences or similarities are during the symptomatic at-risk stage of RA, i.e. clinically suspect arthralgia (CSA). To deepen insights into these differences/similarities, we compared the course of symptoms/impairments and subclinical joint inflammation in the CSA phase during progression to inflammatory arthritis (IA) or to CSA resolution., Methods: A total of 845 CSA patients were followed for a median of 24 months; 136 patients developed IA and an additional 355/505 patients had resolution of CSA according to rheumatologists. Patient burden (pain, morning stiffness, fatigue, functional disabilities, presenteeism) was assessed at baseline and 4, 12 and 24 months and at IA development. Subclinical joint inflammation in the hands and feet was assessed over time with 1.5T MRI. Linear and Poisson mixed models were used., Results: In both ACPA-positive and ACPA-negative patients, patient burden increased towards IA development and decreased towards CSA resolution. However, patient burden was lower in ACPA-positive vs ACPA-negative disease at all timepoints. Conversely, subclinical joint inflammation tended to increase more rapidly during development of ACPA-positive IA [incidence rate ratio (IRR) 1.52 (95% CI 0.94, 2.47), P = 0.089] and remained higher over time in ACPA-positive CSA patients achieving resolution compared with ACPA-negative patients [IRR 1.52 (95% CI 1.07, 2.15), P = 0.018]. Although correlation coefficients between changes in patient burden and subclinical joint inflammation during progression to IA were weak, they were consistently higher in ACPA-positive than ACPA-negative disease, e.g. ρ = 0.29 vs 0.12 for functional disabilities., Conclusion: During RA development and CSA resolution, ACPA-positive CSA patients have lower patient burden but more subclinical joint inflammation than ACPA-negative CSA patients. These data strengthen the notion that the development of ACPA-positive and ACPA-negative RA is pathophysiologically different and encourage further research on these differences., (© The Author(s) 2024. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Objectives: Obesity is a known risk factor for developing rheumatoid arthritis (RA). However, it is unclear whether obesity exerts its risk effect during the asymptomatic or the symptomatic clinically suspect arthralgia (CSA) phase of risk. To improve understanding of the effect of obesity on RA development, we aimed to (1) compare body mass index (BMI) at CSA onset to BMI of the general population and (2) study within CSA patients if obesity increases the risk for progression to RA., Methods: 1107 symptomatic persons at risk for RA from four cohorts (CSA Leiden, CSA Rotterdam, SONAR and TREAT EARLIER placebo arm) were studied. For the first aim, baseline BMI was compared with age-matched/sex-matched BMI of the general population. Patients were stratified for anticitrullinated protein antibody (ACPA) status. Regarding the second aim, the association between BMI and inflammatory arthritis (IA) development during 2 years was studied with Cox regression analysis within each cohort and via meta-analysis in all cohorts., Results: CSA patients of all cohorts were more often obese than the general population (respectively 21.9% vs 14.0%, 25.7% vs 14.5%, 26.7% vs 14.5% and 33.3% vs 14.9%, in CSA Leiden, CSA Rotterdam, SONAR, TREAT EARLIER placebo arm). Both ACPA-positive and ACPA-negative CSA patients had a higher frequency of obesity. Within CSA, obesity was not associated with IA development compared to normal weight (pooled effect in meta-analysis of four cohorts HR 1.01 (95% CI 0.93 to 1.08))., Conclusions: Obesity is not associated with RA development within CSA patients but BMI has already increased in CSA compared to the general population. Obesity, therefore, presumably exerts its risk effect at an early asymptomatic phase of RA development, rather than being associated with the disease processes that ultimately result in clinical arthritis., Competing Interests: Competing interests: AvdH is an editorial board member for RMDopen. Otherwise none., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: The natural trajectory of clinical arthritis progression at the tissue level remains elusive. We hypothesized that subclinical inflammation in different joint tissues (synovitis, tenosynovitis, osteitis) increases in a distinct temporal order in patients with clinically suspect arthralgia (CSA) who develop rheumatoid arthritis (RA) and subsides in a different sequence when CSA spontaneously resolves., Methods: We studied 185 serial magnetic resonance images (MRIs) from CSA patients with subclinical joint inflammation from the placebo arm of the TREAT EARLIER trial: 52 MRIs from 21 RA progressors (MRIs conducted at 1 year before, at 4 months before, and upon RA development), and 133 MRIs from 35 patients with spontaneous resolution of pain (MRIs conducted at baseline and at 4, 12, and 24 months). MRIs were scored for osteitis, synovitis, and tenosynovitis. We used cross-lagged models to evaluate 2 types of time patterns between pairs of inflamed tissues: a simultaneous pattern (coinciding changes) and a subsequent pattern (inflammatory changes in 1 tissue preceding changes in another tissue)., Results: In patients who developed RA, synovitis, tenosynovitis, and osteitis increased simultaneously. Increasing osteitis occurred in the final 4 months before RA diagnosis, following incremental tenosynovitis and synovitis changes during the 1 year to 4 months before diagnosis (P < 0.01). In anti-citrullinated protein antibody (ACPA)-positive and ACPA-negative patients who progressed to RA, osteitis increased just before RA development. In patients with pain resolution, simultaneous decreases in synovitis, tenosynovitis, and osteitis occurred, with tenosynovitis decreasing in the first 4 months after CSA onset preceding decreasing synovitis and osteitis during 4-12 months (P = 0.02 and P < 0.01)., Conclusion: We identified natural sequences of subclinical inflammation in different joint tissues, which deepens our understanding of clinical arthritis and RA development. During RA progression, increasing osteitis followed previous increases in tenosynovitis and synovitis. During pain resolution, tenosynovitis decreased first, followed by decreasing synovitis and osteitis., (© 2023 The Authors. Arthritis & Rheumatology published by Wiley Periodicals LLC on behalf of American College of Rheumatology.)

Competing Interests: We declare no competing interests. This study was carried out in compliance with the Helsinki declaration and all patients provided written informed consent. The study was approved by the medical ethical committee of the Leiden University Medical Centre. The TREAT EARLIER trial is registered with the Netherlands Trials Registry (NTR4853-trial-NL4599). This work was supported by a ZonMW grant (programma translationeel onderzoek), by the European Research Council under the EU's Horizon 2020 research and innovation programme (Starting grant, agreement No 714312), and the Dutch Arthritis Society. The funder had no role in analysis and interpretation of the data, or writing of the manuscript.

Objectives: While awaiting therapies accomplishing rheumatoid arthritis (RA)-prevention in individuals at-risk, recent evidence supports that a 1-year methotrexate treatment may lead to sustained reduction in disease burden and subclinical joint inflammation in patients with clinically suspect arthralgia (CSA). We aimed to study the previously unexplored attitudes of CSA patients and rheumatologists on 1-year DMARD treatment in the arthralgia phase to reduce the disease burden, while not preventing RA., Methods: CSA patients who participated in the TREAT EARLIER trial, thus being expert by experience, were informed on the trial results. Thereafter they completed an anonymous questionnaire about their attitudes on treatment in the CSA phase. We used the same approach for Dutch healthcare professionals in rheumatology., Results: The majority of trial participants (85%) considered the effects of the 1-year treatment as found in the TREAT EARLIER trial, beneficial in the symptomatic at-risk stage. 79% would recommend a 1-year methotrexate course to others with comparable joint complaints. Two-thirds indicated RA prevention and improving disease burden to be equally important treatment goals in the CSA phase. Most healthcare professionals (88%) were inclined to prescribe 1-year treatment to CSA patients aimed at long-term improvement of symptoms and functioning, while not preventing RA development. 59% believed the profits of a 1-year methotrexate course to outweigh disadvantages, for example, side effects., Conclusions: A considerable willingness exists among CSA patients and rheumatologists to start a 1-year treatment resulting in long-term improvement of symptoms and functioning, while not preventing RA. This emphasises the need for more research optimising treatment regimens and disease monitoring in individuals at-risk to facilitate such treatment decisions in the future, while avoiding an intervention, either limited or for a prolonged period, which may have harms that outweigh benefits., Trial Registration Number: The Netherlands Trials Registry (NTR4853-trial-NL4599). EudraCT number: NL2014-004472-35., Competing Interests: Competing interests: AvdH is an editorial board member for RMDopen. Otherwise none., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: It is unknown whether rheumatoid arthritis (RA) starts in hands or feet. To investigate this, we performed functional, clinical and imaging studies during progression from clinically suspect arthralgia (CSA) to RA. Additionally, we studied whether functional disabilities of hands/feet at CSA onset contribute to predicting RA development., Methods: 600 patients with CSA were followed for clinical inflammatory arthritis (IA) during median follow-up of 25 months, during which 99 developed IA. Functional disabilities were measured at baseline/4/12/24 months with the Health Assessment Questionnaire Disability Index (HAQ); HAQ items assessing hand disabilities and foot disabilities were selected. The course of disabilities towards IA development (here considered as t=0) was depicted by increasing incidences and analysed using linear mixed models. To evaluate robustness of findings, tender hand/foot joints and subclinical joint inflammation (measured with CE-1.5TMRI) of hand/foot were additionally studied. Associations between disabilities at CSA presentation (here t=0) and future IA development were studied using Cox regression in the total CSA population., Results: During IA development, hand disabilities occurred earlier and more frequently than foot disabilities. Despite both hand disabilities and foot disabilities rose significantly towards IA development, hand disabilities were more severe during this course (mean difference over time: 0.41 units, 95% CI 0.28 to 0.55, p<0.001, on a range 0-3). Similar to functional disabilities, tender joints and subclinical joint inflammation occurred earlier in the hands than feet. In the total CSA population, a single HAQ question on difficulties with dressing (hand functioning) was independently predictive for IA development: HR=2.2, 95% CI 1.4 to 3.5, p=0.001., Conclusion: Evaluation of functional disabilities, supported by clinical and imaging findings, revealed that joint involvement starts predominantly in the hands during RA development. Additionally, a single question on dressing difficulties adds value to risk stratification in patients with CSA., Competing Interests: Competing interests: AvdH is an Editorial Board Member for RMDopen., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Clinically suspect arthralgia (CSA) is characterised by arthralgia of small joints and considered a risk stage for development of rheumatoid arthritis (RA). However, it remains unknown if the function of the hands is already affected and what mechanisms underlie impaired hand-function in CSA., Methods: We studied various measures of hand function in two CSA populations. CSA patients in the TREAT EARLIER-trial (n=236) were evaluated at baseline for: grip strength on a dynamometer (GS), patient-reported difficulties in the grip domain of the Health Assessment Questionnaire (HAQ) questionnaire and incomplete fist closure at physical examination. Findings were validated in an independent CSA cohort (n=600) where hand function was measured as: GS evaluated by squeezing the examiner's fingers, grip domain of the HAQ questionnaire and fist closure. Contrast-enhanced MRI of the hands measured synovitis, tenosynovitis and bone marrow oedema (summed as subclinical inflammation) in both cohorts., Results: GS (on a dynamometer) was reduced in 75% compared with reference values in healthy controls, 60% reported grip difficulties and 13% had incomplete fist closure. Reduced GS was associated with subclinical inflammation (-0.38 kg/point inflammation, 95% CI -0.68 to -0.08). Studying separate MRI features, GS reduction was independently associated with tenosynovitis, decreasing with -2.63 kg (95% CI -2.26 to -0.33)/point tenosynovitis (range observed tenosynovitis scores: 0-20). Similar relations with tenosynovitis were seen for patient-reported grip difficulties (OR 1.12/point, 95% CI 1.07 to 1.42) and incomplete fist closure (OR 1.36/point, 95% CI 1.03 to 1.79). In the validation cohort, 36% had decreased examiner-assessed GS, 51% reported grip difficulties and 14% incomplete fist closure: all were associated with tenosynovitis. Decreased dynamometer-measured GS was most sensitive for detecting tenosynovitis (75%), while incomplete fist closure was most specific (88%-90%)., Conclusion: Hand function is already often affected before RA development. These limitations are related to subclinical inflammation and tenosynovitis in particular., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: The squeeze test of MTP joints is frequently used because it is easy and cheap. It is traditionally perceived as a test for synovitis. Besides classic intra-articular synovitis, also tenosynovitis and intermetatarsal bursitis (IMB) represent synovial inflammation, albeit juxta-articularly located. Both are frequently present in RA and occasionally in other arthritides. Therefore we hypothesized that tenosynovitis and IMB contribute to a positive MTP squeeze test., Methods: A cross-sectional study design was used. A total of 192 early arthritis patients and 693 clinically suspect arthralgia patients underwent the MTP squeeze test and forefoot MRI at first presentation. MRI measurements in age-matched healthy controls were used to define positivity for synovitis, tenosynovitis and IMB. Logistic regression was used., Results: In early arthritis patients, synovitis [odds ratio (OR) 4.8 (95% CI 2.5, 9.5)], tenosynovitis [2.4 (1.2, 4.7)] and IMB [1.7 (1.2, 2.6)] associated with MTP squeeze test positivity. Synovitis [OR 3.2 (95% CI 1.4, 7.2)] and IMB [3.9 (1.7, 8.8)] remained associated in multivariable analyses. Of patients with a positive MTP squeeze test, 79% had synovitis or IMB: 12% synovitis, 15% IMB and 52% both synovitis and IMB. In clinically suspect arthralgia patients, subclinical synovitis [OR 3.0 (95% CI 2.0, 4.7)], tenosynovitis [2.7 (1.6, 4.6)] and IMB [1.7 (1.2, 2.6)] associated with MTP squeeze test positivity, with the strongest association for synovitis in multivariable analysis. Of positive MTP squeeze tests, 39% had synovitis or IMB (10% synovitis, 15% IMB and 13% both synovitis and IMB)., Conclusion: Besides synovitis, IMB contributes to pain upon compression in early arthritis, presumably due to its location between MTP joints. This is the first evidence showing that MTP squeeze test positivity is not only explained by intra- but also juxta-articular inflammation., (© The Author(s) 2022. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Background: Rheumatoid arthritis is the most common autoimmune disease worldwide and requires long-term treatment to suppress inflammation. Currently, treatment is started when arthritis is clinically apparent. We aimed to evaluate whether earlier intervention, in the preceding phase of arthralgia and subclinical joint inflammation, could prevent the development of clinical arthritis or reduce the disease burden., Methods: We conducted a randomised, double-blind, placebo-controlled, proof-of-concept-trial at the Leiden University Medical Centre, Leiden, Netherlands. Adults aged 18 years or older with arthralgia clinically suspected of progressing to rheumatoid arthritis and MRI-detected subclinical joint inflammation were eligible for enrolment across 13 rheumatology outpatient clinics in the southwest region of the Netherlands and randomly assigned (1:1) to a single intramuscular glucocorticoid injection (120 mg) and a 1-year course of oral methotrexate (up to 25 mg/week), or placebo (single injection and tablets for 1 year). Participants and investigators were masked to group assignment. Follow-up continued for 1 year after the end of the 1-year treatment period. The primary endpoint was development of clinical arthritis (fulfilling the 2010 rheumatoid arthritis classification criteria or involving two or more joints) that persisted for at least 2 weeks. Patient-reported physical functioning, symptoms, and work productivity were secondary endpoints, which were measured every 4 months. Additionally, the course of MRI-detected inflammation was studied. All participants entered the intention-to-treat analysis. This trial is registered with EudraCT, 2014-004472-35, and the Netherlands Trial Register, NTR4853-trial-NL4599., Findings: Between April 16, 2015, and Sept 11, 2019, 901 patients were assessed for eligibility and 236 were enrolled and randomly assigned to active treatment (n=119) or placebo (n=117). At 2 years, the frequency of the primary endpoint was similar between the groups (23 [19%] of 119 participants in the treatment group vs 21 [18%] of 117 in the placebo group; hazard ratio 0·81, 95% CI 0·45 to 1·48). Physical functioning improved more in the treatment group during the first 4 months and remained better than in the placebo group (mean between-group difference in Health Assessment Questionnaire disability index over 2 years: -0·09, 95% CI -0·16 to -0·03; p=0·0042). Similarly, pain (on scale 0-100, mean between-group difference: -8, 95% CI -12 to -4; p<0·0001), morning stiffness of joints (-12, -16 to -8; p<0·0001), presenteeism (-8%, -13 to -3; p=0·0007), and MRI-detected joint inflammation (-1·4 points, -2·0 to -0·9; p<0·0001) showed sustained improvement in the treatment group compared with the placebo group. The number of serious adverse events was equal in both groups; adverse events were consistent with the known safety profile for methotrexate., Interpretation: Methotrexate, the cornerstone treatment of rheumatoid arthritis, initiated at the pre-arthritis stage of symptoms and subclinical inflammation, did not prevent the development of clinical arthritis, but modified the disease course as shown by sustained improvement in MRI-detected inflammation, related symptoms, and impairments compared with placebo., Funding: Dutch Research Council (NWO; Dutch Arthritis Society)., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Objectives: Morning stiffness (MS) is characteristic of RA and associates with markers of systemic and local inflammation in RA patients. In patients with arthralgia, MS is a cardinal symptom to recognize arthralgia at-risk for RA development [i.e. clinically suspect arthralgia (CSA)]. In CSA, MS is also assumed to reflect inflammation, but this has never been studied. Therefore we aimed to study whether MS in CSA patients is associated with systemic and subclinical joint inflammation., Methods: A total of 575 patients presenting with CSA underwent laboratory investigations and contrast-enhanced 1.5 T MRI of the hand and forefoot (scored according to the Rheumatoid Arthritis MRI Score method). Associations of MS (duration ≥60 min) with the presence of subclinical joint inflammation (synovitis, tenosynovitis and osteitis) and increased CRP (≥5 mg/l) were determined with logistic regression. Additionally, the effect of MS duration (≥30, ≥60 and ≥120 min) was studied., Results: A total of 195 (34%) CSA patients experienced MS. These patients more often had subclinical synovitis [34% vs 21%; odds ratio (OR) 1.95 (95% CI 1.32, 2.87)], subclinical tenosynovitis [36% vs 26%; OR 1.59 (95% CI 1.10, 2.31)] and increased CRP [31% vs 19%; OR 1.93 (95% CI 1.30, 2.88)] than patients without MS. In multivariable analyses, subclinical synovitis [OR 1.77 (95% CI 1.16, 2.69)] and CRP [OR 1.78 (95% CI 1.17-2.69)] remained independently associated with MS. In CSA patients who later developed RA, and thus in retrospect were 'pre-RA' at the time of CSA, MS was more strongly associated with subclinical synovitis [OR 2.56 (95% CI 1.04, 6.52)] and CRP [OR 3.86 (95% CI 1.45, 10.24)]. Furthermore, associations increased with longer MS durations., Conclusion: Inflammation associates with MS in the CSA phase that preceded clinical arthritis. These results increase our understanding of MS when assessing arthralgia in clinical practice., (© The Author(s) 2021. Published by Oxford University Press on behalf of the British Society for Rheumatology.)

Animals have circadian clocks that govern their activity pattern, resulting in 24h rhythms in physiology and behaviour. Under laboratory conditions, light is the major external signal that affects temporal patterns in behaviour, and Mus musculus is strictly nocturnal in its behaviour. In the present study we questioned whether under natural conditions, environmental factors other than light affect the temporal profile of mice. In order to test this, we investigated the activity patterns of free-ranging M. musculus in a natural habitat, using sensors and a camera integrated into a recording unit that the mice could freely enter and leave. Our data show that mice have seasonal fluctuations in activity duration (6.7±0.82 h in summer, 11.3±1.80 h in winter). Furthermore, although primarily nocturnal, wild mice also exhibit daytime activity from spring until late autumn. A multivariate analysis revealed that the major factor correlating with increased daytime activity was population activity, defined as the number of visits to the recording site. Day length had a small but significant effect. Further analysis revealed that the relative population activity (compared to the past couple of days) is a better predictor of daytime activity than absolute population activity. Light intensity and temperature did not have a significant effect on daytime activity. The amount of variance explained by external factors is 51.9%, leaving surprisingly little unexplained variance that might be attributed to the internal clock. Our data further indicate that mice determine population activity by comparing a given night with the preceding 2-7 nights, a time frame suggesting a role for olfactory cues. We conclude that relative population activity is a major factor controlling the temporal activity patterns of M. musculus in an unrestricted natural population., (Copyright © 2014 Elsevier Inc. All rights reserved.)