Prevalence of low hemoglobin levels and associations with other disease parameters in rheumatoid arthritis patients: evidence from the CORRONA registry

OBJECTIVE

To estimate the prevalence of low hemoglobin (Hb) levels in a large US cohort of patients with rheumatoid arthritis (RA) and examine the relationship between Hb levels and RA severity, associated comorbidities, and quality-of-life parameters by cross-sectional analysis of data from the Consortium of Rheumatology Researchers of North America (CORRONA) registry.

METHODS

The study population comprised patients with RA >18 years of age and clinical information recorded in the CORRONA registry between October 1, 2001 and February 1, 2007. Patients were separated into low (Hb <13 g/dl for men; <12 g/dl for women) and normal Hb groups (Hb >13 g/dl for men; >12 g/dl for women). Hb levels were calculated from recorded hematocrit values.

RESULTS

Of the 10,397 study patients, 1734 (16.7%) had low Hb levels and 8663 (83.3%) had normal Hb levels. More patients in the low Hb group had a history of comorbid cardiovascular disease, diabetes, and gastrointestinal disease. The low Hb group exhibited greater disease severity and activity (p<0.05) as reported by patients and rheumatologists. In multivariate analyses, RA severity ([odds ratio] OR 1.24; 95% confidence interval [CI]: 1.07-1.44) and ESR (OR 1.04; 95% CI: 1.03-1.05), and comorbid bleeding ulcers (OR 2.04; 95% CI: 1.01-4.12) were predictive of low Hb levels.

CONCLUSION

Despite changes in treatment paradigms, low Hb levels remain prevalent in RA patients. This analysis suggests that low Hb levels may be associated with RA disease severity and the presence of certain comorbidities.

Association of methotrexate and tumour necrosis factor antagonists with risk of infectious outcomes including opportunistic infections in the CORRONA registry

OBJECTIVE

To examine the association of methotrexate (MTX) and tumour necrosis factor (TNF) antagonists with the risk of infectious outcomes including opportunistic infections in patients with rheumatoid arthritis (RA).

METHODS

Patients with RA enrolled in the Consortium of Rheumatology Researchers of North America (CORRONA) registry prescribed MTX, TNF antagonists or other disease-modifying antirheumatic drugs (DMARDs) were included. The primary outcomes were incident overall and opportunistic infections. Incident rate ratios were calculated using generalised estimating equation Poisson regression models adjusted for demographics, comorbidities and RA disease activity measures.

RESULTS

A total of 7971 patients with RA were followed. The adjusted rate of infections per 100 person-years was increased among users of MTX (30.9, 95% CI 29.2 to 32.7), TNF antagonists (40.1, 95% CI 37.0 to 43.4) and a combination of MTX and TNF antagonists (37.1, 95% CI 34.9 to 39.3) compared with users of other non-biological DMARDs (24.5, 95% CI 21.8 to 27.5). The adjusted incidence rate ratio (IRR) was increased in patients treated with MTX (IRR 1.30, 95% CI 1.12 to 1.50) and TNF antagonists (IRR 1.52, 95% CI 1.30 to 1.78) compared with those treated with other DMARDs. TNF antagonist use was associated with an increased risk of opportunistic infections (IRR 1.67, 95% CI 0.95 to 2.94). Prednisone use was associated with an increased risk of opportunistic infections (IRR 1.63, 95% CI 1.20 to 2.21) and an increased risk of overall infection at doses >10 mg daily (IRR 1.30, 95% CI 1.11 to 1.53).

CONCLUSIONS

MTX, TNF antagonists and prednisone at doses >10 mg daily were associated with increased risks of overall infections. Low-dose prednisone and TNF antagonists (but not MTX) increased the risk of opportunistic infections.

Abatacept inhibits progression of structural damage in rheumatoid arthritis: results from the long-term extension of the AIM trial

OBJECTIVE

Assess the effect of abatacept on progression of structural damage over 2 years in patients with rheumatoid arthritis who had an inadequate response to methotrexate.

METHODS

539 patients entered an open-label extension of the AIM (Abatacept in Inadequate responders to Methotrexate) trial and received abatacept. Radiographic assessment of the hands and feet was performed at baseline, year 1 and year 2. At year 2, each patient's radiographs were scored for progression blinded to sequence and treatment allocation.

RESULTS

In patients treated with abatacept for 2 years, greater reduction in progression of structural damage was observed in year 2 than in year 1. The mean change in total Genant-modified Sharp scores was reduced from 1.07 units in year 1 to 0.46 units in year 2. Similar reductions were observed in erosion and joint space narrowing scores. Following 2 years of treatment with abatacept, 50% of patients had no progression of structural damage as defined by a change in the total score of < or =0 compared with baseline. 56% of patients treated with abatacept had no progression during the first year compared with 45% of patients treated with placebo. In their second year of treatment with abatacept, more patients had no progression than in the first year (66% vs 56%).

CONCLUSIONS

Abatacept has a sustained effect that inhibits progression of structural damage. Furthermore, the mean change in radiographic progression in patients treated with abatacept for 2 years was significantly lower in year 2 versus year 1, suggesting that abatacept may have an increasing disease-modifying effect on structural damage over time.

The CORRONA database

BACKGROUND

Large, long-term databases are needed in order to provide information on the safety and efficacy of new agents used in the treatment of rheumatoid arthritis (RA) and psoriatic arthritis (PsA). These databases can provide data which is well beyond what is available from industry-sponsored investigations.

METHODS

The structure, governance, content, context and developmental plan of the CORRONA database is described.

RESULTS

The CORRONA database has grown from start up in 2002 to the largest independent database in North America which collects data from both rheumatologists and patients at the time of a clinical encounter. Data are collected as often as every 3 months in RA and every 6 months in PsA. As of the time of this writing, the CORRONA database consists of approximately 9,000 patients with RA and 1,000 with PsA. Data can be used to elucidate toxicities found in frequencies which would be considerably less common than can be uncovered in industry-sponsored investigations. In addition, actual prescribing patterns and responses in clinical practice can be investigated and described.

CONCLUSION

After 3 years of data collection, the CORRONA database is now appropriately able to make significant contributions to our understanding of the safety, efficacy of drugs, as well as demographic, and socioeconomic profiles of patients with RA and PsA. It has evolved from a nascent database to a mature one poised to make significant contributions.

Methotrexate dosage reduction in patients with rheumatoid arthritis beginning therapy with infliximab: the Infliximab Rheumatoid Arthritis Methotrexate Tapering (iRAMT) trial

OBJECTIVE

Infliximab plus methotrexate (MTX) is approved for the treatment of rheumatoid arthritis (RA). Based on the benefit/risk profile of this combination therapy, lower doses of MTX would be preferable when infliximab efficacy can be maintained. We evaluated the ability of patients receiving infliximab plus MTX to achieve and maintain a clinical response while the dose of MTX was tapered.

METHODS

Infliximab infusions were administered at a minimum dosage of 3 mg/kg at 8-week intervals (following three loading doses at weeks 0, 2, and 6) to patients who had an inadequate response to MTX. MTX tapering was initiated at week 22 or later when at least a 40% improvement in the combined tender and swollen joint count was achieved; dosages were reduced by 5 mg every 8 weeks to a protocol-specified minimum dosage of 5 mg per week. If the required dosage of MTX after a flare was greater than the baseline dosage, the patient was considered a treatment failure.

RESULTS

Of the 210 patients enrolled, 159 (76%) achieved a 40% or better improvement in the combined tender and swollen joint count and had their MTX doses tapered. In these 159 responders, the median (mean) dose of MTX was reduced from 15 (16.5) mg per week at baseline to 5 (7.1) mg per week at week 54. From the time of initial response, 79% of these patients had a zero- or a one-vial increase in infliximab, corresponding to an approximate dose increase of 1 mg/kg, through week 54.

CONCLUSION

Approximately 75% of the patients participating in this trial achieved at least a 40% reduction in the combined swollen and tender joint count (correlating with an American College of Rheumatology 20% [ACR20] response in 83% of patients) while reducing the mean MTX dose by 57%.

Benefit/risk of leflunomide in rheumatoid arthritis

Leflunomide was first shown to have disease-modifying properties in a rat model of adjuvant-induced arthritis. Leflunomide has been subsequently used with success in several animal models of tissue and organ allograft and of autoimmune disease including collagen- and adjuvant-induced arthritis, interstitial nephritis, myasthenia gravis, and systemic lupus erythematosus. Based on its success as an immunosuppressive agent in these models, leflunomide was tested for the treatment of rheumatoid arthritis (RA).

A randomized, double-blind, crossover clinical trial of diclofenac plus misoprostol versus acetaminophen in patients with osteoarthritis of the hip or knee

OBJECTIVE

To perform a randomized, double-blind, crossover clinical trial of diclofenac + misoprostol versus acetaminophen in ambulatory patients with osteoarthritis of the hip or knee.

METHODS

Patients in 12 ambulatory care settings were eligible if they were age >40 years and if they had Kellgren/Lawrence radiographic grade 2-4 osteoarthritis of the knee or hip and a score of > or =30 mm on a 100-mm visual analog pain scale. Patients were randomized to one of two groups, 75 mg diclofenac + 200 microg misoprostol twice daily or 1,000 mg acetaminophen 4 times daily (each for 6 weeks), and were then crossed over to the other treatment for 6 weeks. A placebo was included in each treatment regimen to enable double blinding. The primary outcome measures were the Western Ontario and McMaster Universities Osteoarthritis Index and the visual analog pain scale of the Multidimensional Health Assessment Questionnaire. Safety was assessed using a standard form to review adverse events.

RESULTS

We enrolled 227 patients, of whom 218 provided data for the first treatment period and 181 provided data for both treatment periods. Significantly higher levels of improvement in the primary outcomes were seen for diclofenac + misoprostol than for acetaminophen (P < 0.001). Adverse events were more common when patients took diclofenac + misoprostol (P = 0.046). Diclofenac + misoprostol was rated as "better" or "much better" by 57% of the 174 patients who provided such ratings for both treatment periods, while acetaminophen was rated as "better" or "much better" by 20% of these patients, and 22% reported no difference (P < 0.001). Differences favoring diclofenac + misoprostol over acetaminophen were greater in patients with more severe osteoarthritis according to baseline pain scores, radiographs, or number of involved joints.

CONCLUSION

Patients with osteoarthritis of the hip or knee had significantly greater improvements in pain scores over 6 weeks with diclofenac + misoprostol than with acetaminophen, although patients with mild osteoarthritis had similar improvements with both drugs. Acetaminophen was associated with fewer adverse events.

Rational use of new and existing disease-modifying agents in rheumatoid arthritis

Because of radiographic evidence of progressive bone loss and the inability to eliminate synovial proliferation with methotrexate, it became apparent that therapy for rheumatoid arthritis needed further advancement. Methotrexate is not a remission-inducing drug and may have dose-limiting toxicity. In the past 2 years, three new disease-modifying antirheumatic drugs (DMARDs) have been approved: leflunomide, etanercept, and infliximab. Each of these agents has demonstrated efficacy compared with placebo in randomized, controlled studies. Because methotrexate had a dominant therapeutic role, the new drugs were also studied in combination with it. Other established DMARDs, such as sulfasalazine and hydroxychloroquine, have also demonstrated efficacy when used together with methotrexate. The results of these combination studies clearly demonstrate that clinical responses can be meaningfully improved when new and existing DMARDs are added to methotrexate. Although toxicity remains a serious concern when powerful immune modulators and antimetabolites are used in combination, relatively few serious adverse events have been reported during 2-year treatment periods. It has also become apparent that combinations of new DMARDs and methotrexate virtually halt radiographic progression over 2 years. The new agents are expensive, but annual costs must be weighed against the personal and societal expense of joint arthroplasty, hospitalizations, disability, and diminished quality of life that accompanies poorly controlled rheumatoid arthritis. The ultimate value of combination DMARD therapy with methotrexate will be determined by long-term data on safety, efficacy, and effects on radiographic deterioration of bone. Additional long-term observational data on the incidence of joint arthroplasty and disability will help to place the issue of societal costs in a better perspective. This will allow the value of aggressive treatment to be established with certainty.

Leflunomide for the treatment of rheumatoid arthritis

Leflunomide treatment appears to offer an alternative to methotrexate and sulfasalazine and is a welcome addition to the therapeutic armamentarium for treating active RA. Leflunomide treatment for more than 12 months results in clinically meaningful improvements in disease-specific measures of physical function. The phase 3 trials have shown leflunomide to be as effective as methotrexate and sulfasalazine and an option for initial DMARD therapy. As with all new agents, the long-term safety and value of leflunomide will be determined by use in the clinic.

n-3 fatty acid supplements in rheumatoid arthritis

Ingestion of dietary supplements of n-3 fatty acids has been consistently shown to reduce both the number of tender joints on physical examination and the amount of morning stiffness in patients with rheumatoid arthritis. In these cases, supplements were consumed daily in addition to background medications and the clinical benefits of the n-3 fatty acids were not apparent until they were consumed for > or =12 wk. It appears that a minimum daily dose of 3 g eicosapentaenoic and docosahexaenoic acids is necessary to derive the expected benefits. These doses of n-3 fatty acids are associated with significant reductions in the release of leukotriene B(4) from stimulated neutrophils and of interleukin 1 from monocytes. Both of these mediators of inflammation are thought to contribute to the inflammatory events that occur in the rheumatoid arthritis disease process. Several investigators have reported that rheumatoid arthritis patients consuming n-3 dietary supplements were able to lower or discontinue their background doses of nonsteroidal antiinflammatory drugs or disease-modifying antirheumatic drugs. Because the methods used to determine whether patients taking n-3 supplements can discontinue taking these agents are variable, confirmatory and definitive studies are needed to settle this issue. n-3 Fatty acids have virtually no reported serious toxicity in the dose range used in rheumatoid arthritis and are generally very well tolerated.

Combination therapy with multiple disease-modifying antirheumatic drugs in rheumatoid arthritis: a preventive strategy

The traditional "pyramid" or sequential approach to treatment of patients with rheumatoid arthritis involved use of a nonsteroidal anti-inflammatory drug for months to years while seeking to avoid use of second-line antirheumatic drugs until evidence of joint damage was seen. This approach led to short-term reduction of inflammation and a few remissions. However, long-term remissions were rare, and most patients experienced poor long-term outcomes, including joint destruction, severe functional declines, considerable economic losses, work disability, and premature mortality. At this time, a "preventive" strategy is evolving in which early aggressive treatment with disease-modifying antirheumatic drugs is used, seeking to minimize long-term joint damage. When residual inflammation remains after maximum doses of single agents, as is usually the case, combinations of disease-modifying antirheumatic drugs appear to be a reasonable consideration for many patients. Methotrexate is the most commonly used "anchor drug" in combination therapy. Evidence from randomized, controlled clinical trials and observational studies have indicated increased efficacy and acceptable (and often lower) toxicity for combinations of methotrexate plus cyclosporine, hydroxychloroquine, sulfasalazine, leflunomide, etanercept, and infliximab. Further studies lasting 5 years or more are needed to determine the long-term effectiveness, toxicities, and optimal clinical use of disease-modifying antirheumatic drug combinations. At this time, such combinations are taken by at least some patients under care of almost all rheumatologists, and it appears likely that they will be used increasingly in the coming decades.

Methotrexate and leflunomide combination therapy for patients with active rheumatoid arthritis

An open-label, one-year study was conducted to evaluate the safety and clinical response to leflunomide and methotrexate combination therapy for rheumatoid arthritis. Study results revealed tolerable safety, no significant pharmacokinetic interactions between methotrexate and leflunomide, and suggested improved clinical response with combination therapy.

Methotrexate and emerging therapies

More publications in the medical literature have described the clinical efficacy and toxicity of methotrexate (MTX) than of any other drug ever used for rheumatic diseases. A knowledgeable clinical can thus rely on evidence-based medicine to guide the use of this agent. Because MTX is not remission-inducing, many new therapies are being combined with it in order to achieve a greater therapeutic response. This trend will likely continue and expand as more novel agents are introduced.

Methotrexate and leflunomide: biochemical basis for combination therapy in the treatment of rheumatoid arthritis

OBJECTIVES

Methotrexate is currently one of the most widely prescribed disease-modifying antirheumatic drugs (DMARDs) for the treatment of rheumatoid arthritis (RA). Combination therapy of methotrexate with other DMARDs increases the clinical success of low-dose methotrexate treatment. Leflunomide is a new DMARD that may have a high potential for success in combination therapy with methotrexate. This review compares the mode of action of methotrexate and leflunomide and speculates on how this contributes to therapeutic efficacy in RA when these agents are used singly or in combination.

METHODS

A literature review of the biochemical mechanisms considered to be the basis for the therapeutic efficacy of methotrexate and leflunomide in treating RA is presented.

RESULTS

Low-dose methotrexate inhibits cytokine production, purine biosynthesis, and, in an animal model, causes the release of adenosine, a potent antiinflammatory agent. Leflunomide, through inhibition of de novo pyrimidine biosynthesis, can regulate lymphocyte proliferation.

CONCLUSIONS

The biochemical mechanisms underlying the therapeutic efficacy of low-dose methotrexate and leflunomide in the treatment of RA are quite different. The potentially complementary mechanisms of action of these two effective DMARDs should provide a rationale for their use in combination therapy for patients whose condition no longer responds to methotrexate alone.

Pharmacokinetics, safety, and efficacy of combination treatment with methotrexate and leflunomide in patients with active rheumatoid arthritis

OBJECTIVE

To examine the safety and pharmacokinetics of and clinical response to leflunomide, a de novo pyrimidine synthesis inhibitor, when administered to patients with active rheumatoid arthritis (RA) who have been receiving long-term methotrexate therapy.

METHODS

This was an open-label, 52-week study in which 30 patients with RA that remained active despite therapy with methotrexate at 17+/-4 mg/week (mean +/- SD) for > or =6 months were given leflunomide, 10-20 mg/day. Patients were assessed for adverse effects, pharmacokinetic measurements of leflunomide and methotrexate, and clinical response by American College of Rheumatology (ACR) 20% response criteria.

RESULTS

Twenty-three patients completed 1 year of treatment. No significant pharmacokinetic interactions between leflunomide and methotrexate were noted. This combination therapy was generally well tolerated clinically, with the exception of elevations of liver enzyme levels. Seven patients withdrew from the treatment regimen: 2 withdrawals were voluntary, 3 were due to persistent elevation of plasma transaminase levels, and 2 were due to lack of efficacy. Of the patients, 16 (53%) met ACR 20% response criteria. Two met ACR criteria for remission after 1 year.

CONCLUSION

The combination of methotrexate and leflunomide has therapeutic potential in RA.

The psychosocial effects of rheumatoid arthritis on the patient and the well partner

Rheumatoid arthritis (RA) is a chronic disorder that can have a severe impact on patient's lives. This present study investigated four questions regarding the psychosocial effects on patients and their well partners. First we found that depression for both patients and partners were slightly elevated and 35.7% of patients and 23.3% of well partners had scores above the cut-off for possible clinical depression on the Center for Epidemiological Studies Depression Scale. Second, there was no significant difference between the patients' level of distress and that of the partners. Third, there were moderate positive correlations between patients' and partners' scores on measure of psychological functioning. Fourth, there were no differences in either the patients' or partners' well-being based on the gender of the patient. Finally, an exploratory analysis was conducted to examine the factors which influence the patients' and partners' depression and their view of the relationship.

A trial of etanercept, a recombinant tumor necrosis factor receptor:Fc fusion protein, in patients with rheumatoid arthritis receiving methotrexate

BACKGROUND

Patients treated with methotrexate for rheumatoid arthritis often improve but continue to have active disease. This study was undertaken to determine whether the addition of etanercept, a soluble tumor necrosis factor receptor (p75):Fc fusion protein (TNFR:Fc), to methotrexate therapy would provide additional benefit to patients who had persistent rheumatoid arthritis despite receiving methotrexate.

METHODS

In a 24-week, double-blind trial, we randomly assigned 89 patients with persistently active rheumatoid arthritis despite at least 6 months of methotrexate therapy at a stable dose of 15 to 25 mg per week (or as low as 10 mg per week for patients unable to tolerate higher doses) to receive either etanercept (25 mg) or placebo subcutaneously twice weekly while continuing to receive methotrexate. The primary measure of clinical response was the American College of Rheumatology criteria for a 20 percent improvement in measures of disease activity (ACR 20) at 24 weeks.

RESULTS

The addition of etanercept to methotrexate therapy resulted in rapid and sustained improvement. At 24 weeks, 71 percent of the patients receiving etanercept plus methotrexate and 27 percent of those receiving placebo plus methotrexate met the ACR 20 criteria (P<0.001); 39 percent of the patients receiving etanercept plus methotrexate and 3 percent of those receiving placebo plus methotrexate met the ACR 50 criteria (for a 50 percent improvement) (P<0.001). Patients receiving etanercept plus methotrexate had significantly better outcomes according to all measures of disease activity. The only adverse events associated with etanercept were mild injection-site reactions, and no patient withdrew from the study because of adverse events associated with etanercept.

CONCLUSIONS

In patients with persistently active rheumatoid arthritis, the combination of etanercept and methotrexate was safe and well tolerated and provided significantly greater clinical benefit than methotrexate alone.

Methotrexate and emerging therapies

It is likely that all new therapeutic interventions will be used with methotrexate in combination therapy. These combinations may yield real therapeutic advances. The potential for end organ toxicity, opportunistic infection, and malignancy will need to be carefully monitored with long-term, meticulously conducted observational studies. Expense, ease of use, and perceived benefit-to-risk ratio will determine which new agents become most commonly prescribed with methotrexate.

Treatment of rheumatoid arthritis with oral type II collagen. Results of a multicenter, double-blind, placebo-controlled trial

OBJECTIVE

Oral administration of cartilage-derived type II collagen (CII) has been shown to ameliorate arthritis in animal models of joint inflammation, and preliminary studies have suggested that this novel therapy is clinically beneficial and safe in patients with rheumatoid arthritis (RA). The present study was undertaken to test the safety and efficacy of 4 different dosages of orally administered CII in patients with RA.

METHODS

Two hundred seventy-four patients with active RA were enrolled at 6 different sites and randomized to receive placebo or 1 of 4 dosages (20, 100, 500, or 2,500 microg/day) of oral CII for 24 weeks. Efficacy parameters were assessed monthly. Cumulative response rates (percentage of patients meeting the criteria for response at any time during the study) were analyzed utilizing 3 sets of composite criteria: the Paulus criteria, the American College of Rheumatology criteria for improvement in RA, and a requirement for > or = 30% reduction in both swollen and tender joint counts.

RESULTS

Eighty-three percent of patients completed 24 weeks of treatment. Numeric trends in favor of the 20 microg/day treatment group were seen with all 3 cumulative composite measures. However, a statistically significant increase (P = 0.035) in response rate for the 20 microg/day group versus placebo was detected using only the Paulus criteria. The presence of serum antibodies to CII at baseline was significantly associated with an increased likelihood of responding to treatment. No treatment-related adverse events were detected. The efficacy seen with the lowest dosage is consistent with the findings of animal studies and with known mechanisms of oral tolerance in which lower doses of orally administered autoantigens preferentially induce disease-suppressing regulatory cells.

CONCLUSION

Positive effects were observed with CII at the lowest dosage tested, and the presence of serum antibodies to CII at baseline may predict response to therapy. No side effects were associated with this novel therapeutic agent. Further controlled studies are required to assess the efficacy of this treatment approach.

Long-term exposure to methotrexate induces immunophenotypic changes, decreased methotrexate uptake and increased dihydrofolate gene copy number in Jurkat T cells

Methotrexate (MTX) treatment of rheumatoid arthritis may require increasing doses to maintain clinical efficacy. An overall plateau of clinical response is reached after only six months of treatment. To study the immunologic, biochemical and genetic effects of MTX on T cells, the Jurkat T cell line was made MTX-resistant by serial addition of methotrexate sodium into culture medium. Cells proliferated and divided successfully in MTX concentrations ranging to 15 microM. MTX resistance of Jurkat T cells in vitro was accompanied by significantly (P < 0.05) decreased expression of CD2, CD3, CD4, CD28, and CD69, IL-2 production, and MTX uptake assessed by cell association or disassociation of 3[H]-MTX or fluoresceinated MTX (FMTX), respectively. In addition, there was DHFR gene amplification and increased levels of DHFR in all resistant cell lines. Both permanent and transient phenotypic changes developed in resultant cell lines exposed to increasing concentrations of MTX in vitro. Expression of CD4 and CD25 and sensitivity to MTX returned to near-parental levels after removal of MTX from culture medium, whereas expression of CD26 and MTX uptake were significantly increased. Expression of CD2, CD3, CD69 and IL-2 production as well as the DHFR levels did not return to the parental phenotype after removal from MTX. We conclude that MTX-cultured cells express depressed levels of cell-surface markers vital for T cell function and activation. The return of enhancement of these cell-surface markers critical to T cell activation suggests a possible mechanism for the severe flares experienced by rheumatoid arthritis patients when drug treatment is discontinued.