Two-year reduction of dual-energy CT urate depositions during a treat-to-target strategy in gout in the NOR-Gout longitudinal study

Sustained xanthine oxidase inhibitor treat to target urate lowering therapy rewires a tight inflammation serum protein interactome

Background

Effective xanthine oxidoreductase inhibition (XOI) urate-lowering treatment (ULT) to target significantly reduces gout flare burden and synovitis between 1-2 years therapy, without clearing all monosodium urate crystal deposits. Paradoxically, treat to target ULT is associated with increased flare activity for at least 1 year in duration on average, before gout flare burden decreases. Since XOI has anti-inflammatory effects, we tested for biomarkers of sustained, effective ULT that alters gouty inflammation.

Methods

We characterized the proteome of febuxostat-treated murine bone marrow macrophages. Blood samples (baseline and 48 weeks ULT) were analyzed by unbiased proteomics in febuxostat and allopurinol ULT responders from two, independent, racially and ethnically distinct comparative effectiveness trial cohorts (n=19, n=30). STRING-db and multivariate analyses supplemented determinations of significantly altered proteins via Wilcoxon matched pairs signed rank testing.

Results

The proteome of cultured IL-1b-stimulated macrophages revealed febuxostat-induced anti-inflammatory changes, including for classical and alternative pathway complement activation pathways. At 48 weeks ULT, with altered purine metabolism confirmed by serum metabolomics, serum urate dropped >30%, to normal (<6.8 mg/dL) in all the studied patients. Overall, flares declined from baseline. Treated gout patient sera and peripheral blood mononuclear cells (PBMCs) showed significantly altered proteins (p<0.05) in clustering and proteome networks. CRP was not a useful therapy response biomarker. By comparison, significant serum proteome changes included decreased complement C8 heterotrimer C8A and C8G chains essential for C5b-9 membrane attack complex assembly and function; increase in the NLRP3 inflammasome activation promoter vimentin; increased urate crystal phagocytosis inhibitor sCD44; increased gouty inflammation pro-resolving mediator TGFB1; decreased phagocyte-recruiting chemokine PPBP/CXCL7, and increased monocyte/macrophage-expressed keratin-related proteins (KRT9,14,16) further validated by PBMC proteomics. STRING-db analyses of significantly altered serum proteins from both cohorts revealed a tight interactome network including central mediators of gouty inflammation (eg, IL-1B, CXCL8, IL6, C5).

Conclusions

Rewiring of inflammation mediators in a tight serum protein interactome was a biomarker of sustained XOI-based ULT that effectively reduced serum urate and gout flares. Monitoring of the serum and PBMC proteome, including for changes in the complement pathway could help determine onset and targets of anti-inflammatory changes in response to effective, sustained XOI-based ULT.Trial Registration: ClinicalTrials.gov Identifier: NCT02579096.

The statistical challenge of analysing changes in dual energy computed tomography (DECT) urate volumes in people with gout

BACKGROUND

Dual energy computed tomography (DECT) allows direct visualization of monosodium urate crystal deposition in gout. However, DECT urate volume data are often highly skewed (mostly small volumes with the remainder considerably larger), making statistical analyses challenging in longitudinal research. The aim of this study was to explore the ability of various analysis methods to normalise DECT urate volume data and determine change in DECT urate volumes over time.

METHODS

Simulated datasets containing baseline and year 1 DECT urate volumes for 100 people with gout were created from two randomised controlled trials. Five methods were used to transform the DECT urate volume data prior to analysis: log-transformation, Box-Cox transformation, log(X-(min(X)-1)) transformation; inverse hyperbolic sine transformation, and rank order. Linear regression analyses were undertaken to determine the change in DECT urate volume between baseline and year 1. Cohen's d were calculated as a measure of effect size for each data treatment method. These analyses were then tested in a validation clinical trial dataset containing baseline and year 1 DECT urate volumes from 91 people with gout.

RESULTS

No data treatment method successfully normalised the distribution of DECT urate volumes. For both simulated and validation data sets, significant reductions in DECT urate volumes were observed between baseline and Year 1 across all data treatment methods and there were no significant differences in Cohen's d effect sizes.

CONCLUSIONS

Normalising highly skewed DECT urate volume data is challenging. Adopting commonly used transformation techniques may not significantly improve the ability to determine differences in measures of central tendency when comparing the change in DECT urate volumes over time.

Emerging Urate-Lowering Drugs and Pharmacologic Treatment Strategies for Gout: A Narrative Review

Hyperuricemia with consequent monosodium urate crystal deposition leads to gout, characterized by painful, incapacitating inflammatory arthritis flares that are also associated with increased cardiovascular event and related mortality risk. This narrative review focuses on emerging pharmacologic urate-lowering treatment (ULT) and management strategies in gout. Undertreated, gout can progress to palpable tophi and joint damage. In oral ULT clinical trials, target serum urate of < 6.0 mg/dL can be achieved in ~ 80-90% of subjects, with flare burden reduction by 1-2 years. However, real-world ULT results are far less successful, due to both singular patient nonadherence and prescriber undertreatment, particularly in primary care, where most patients are managed. Multiple dose titrations commonly needed to optimize first-line allopurinol ULT monotherapy, and substantial potential toxicities and other limitations of approved, marketed oral monotherapy ULT drugs, promote hyperuricemia undertreatment. Common gout comorbidities with associated increased mortality (e.g., moderate-severe chronic kidney disease [CKD], type 2 diabetes, hypertension, atherosclerosis, heart failure) heighten ULT treatment complexity and emphasize unmet needs for better and more rapid clinically significant outcomes, including attenuated gout flare burden. The gout drug armamentarium will be expanded by integrating sodium-glucose cotransporter-2 (SGLT2) inhibitors with uricosuric and anti-inflammatory properties as well as clinically indicated antidiabetic, nephroprotective, and/or cardioprotective effects. The broad ULT developmental pipeline is loaded with multiple uricosurics that selectively target uric acid transporter 1 (URAT1). Evolving ULT approaches include administering selected gut anaerobic purine degrading bacteria (PDB), modulating intestinal urate transport, and employing liver-targeted xanthine oxidoreductase mRNA knockdown. Last, emerging measures to decrease the immunogenicity of systemically administered recombinant uricases should simplify treatment regimens and further improve outcomes in managing the most severe gout phenotypes.

Factors influencing the kinetics of MSU crystal depletion measured with dual-energy CT in patients with gout

OBJECTIVE

To examine factors influencing the kinetics of monosodium urate (MSU) crystal dissolution measured with dual-energy computed tomography (DECT) during follow-up of patients with gout.

METHODS

Patients with a diagnosis of gout with baseline knees and feet DECT scans exhibiting MSU crystal volumes ≥0.1 cm3 and at least one follow-up DECT were included. Spearman's correlation coefficient was used to search for association between change from baseline MSU crystal volume at 6, 12, 18 and 24 months and serum urate (SU) level. Associations between percentage change from the baseline volume of MSU crystal deposits and explanatory variables were assessed using linear mixed models.

RESULTS

Sixty-two patients (age 67.3±12.8 years; 53 (85%) males) cumulating 104 follow-up DECT scans were included. Overall, SU target levels (<6.0 and <5.0 mg/dL) were achieved by 48 (77%) and 36 (58%) patients, respectively. There was a good correlation (r=0.66; p<0.0001) observed between SU level and percentage change in MSU crystal volume. The median decrease from baseline MSU crystal volume was greater in patients reaching the <5.0 mg/dL SU target than in those reaching ≥5.0 SU <6.0 mg/dL: -85% (95% CI: -94% to -72%) versus -40% (-57% to -22%; p<0.05) at 12 months. In multivariable analysis, time (in days) with a multilevel coefficient of -0.06 (95% CI: -0.08 to -0.03, p<0.001), hypertension (coefficient: 41.87, 95% CI: 16.38 to 67.18, p<0.01) and SU level <5.0 mg/dL (coefficient: -39.46, 95% CI: -70.93 to -8.34, p=0.02) were the only variables significantly associated with MSU crystal volume change.

CONCLUSION

In patients with DECT-measured MSU crystal deposition, reaching the <5.0 mg/dL SU target provides more extensive and rapid crystal dissolution than reaching the <6.0 mg/dL SU target.

Uric acid en route to gout

Gout and hyperuricemia (HU) have generated immense attention due to increased prevalence. Gout is a multifactorial metabolic and inflammatory disease that occurs when increased uric acid (UA) induce HU resulting in monosodium urate (MSU) crystal deposition in joints. However, gout pathogenesis does not always involve these events and HU does not always cause a gout flare. Treatment with UA-lowering therapeutics may not prevent or reduce the incidence of gout flare or gout-associated comorbidities. UA exhibits both pro- and anti-inflammation functions in gout pathogenesis. HU and gout share mechanistic and metabolic connections at a systematic level, as shown by studies on associated comorbidities. Recent studies on the interplay between UA, HU, MSU and gout as well as the development of HU and gout in association with metabolic syndromes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular, renal and cerebrovascular diseases are discussed. This review examines current and potential therapeutic regimens and illuminates the journey from disrupted UA to gout.

Musculoskeletal Ultrasound in Monitoring the Efficacy of Gout: A Prospective Study Based on Tophus and Double Contour Sign

Background

In patients with gout receiving uric acid-lowering therapy, musculoskeletal ultrasound has the potential to observe changes in gout lesions.

Aims

To analyze the effectiveness of uric acid-lowering therapy in patients with gout over one year using musculoskeletal ultrasound as a monitoring technique.

Study Design

Prospective cohort study.

Methods

A total of 215 patients meeting the 1977 American College of Rheumatology gout classification criteria and treated with uric acid-lowering therapy were separated into two groups, treat-to-target and treat-to-non-target depending on the target serum urate levels. Lower extremity joints were evaluated by ultrasound before therapy (M₀), as well as three (M₃), six (M₆), and twelve (M₁₂) months after therapy. At various moments during uric acid-lowering therapy, the tophus size and the semiquantitative ultrasound scoring system of double contour sign were measured in the treat-to-target and treat-to-non-target groups.

Results

Ninety-five tophi (45 in treat-to-target and 50 in treat-to-non-target) and sixty-seven double contour sign (34 in treat-to-target and 33 in treat-to-non-target) were evaluated longitudinally. In both groups, the long diameter, short diameter, and area of tophus in treat-to-target decreased as the duration of uric acid-lowering treatment increased. Differences in the long diameter of tophus between M₁₂ and M₀, M₃ and M₆ were statistically significant (P < 0.05), while differences between the other time points were not significant (P > 0.05). No statistically significant differences were observed in the short diameter and the area of tophus between M₀ and M₃ (P > 0.05), while there were statistically significant differences between other periods (P < 0.05). In treat-to-non-target, the long diameter, short diameter, and area of tophus showed a slight increase at different uric acid-lowering therapy time points. The differences in the long diameter, short diameter, and area of tophus at different uric acid-lowering therapy time points were not significant (P > 0.05). The semiquantitative ultrasound scoring system of double contour sign of treat-to-target and treat-to-non-target showed a decreasing trend with increasing uric acid-lowering therapy time, with a more pronounced drop in treat-to-target than treat-to-non-target. In treat-to-target, the difference in the semiquantitative ultrasound scoring system of double contour sign at each uric acidlowering therapy time point was significant (P < 0.05). In treat-tonon- target, the difference in semiquantitative ultrasound scoring system of double contour sign scores between M⁰ and M³ was not statistically significant (P >0.05), but it was statistically significant for the remaining time points (P < 0.05).

Conclusion

After one year of uric acid-lowering therapy in patients with gout, an ultrasound indicated that the size of tophus and the semiquantitative ultrasound scoring system of double contour sign score decreased dramatically in the treat-to-target group. Semiquantitative ultrasound scoring system of double contour sign score was dramatically reduced in the treat-to-non-target group, but the size of the tophus remained the same. Therefore, musculoskeletal ultrasound is an effective tool to monitor the efficacy of uric acid-lowering therapy.

The Singapore Experience With Uncontrolled Gout: Unmet Needs in the Management of Patients

Gout is the most common type of inflammatory arthritis, and its impact on cardiovascular health and quality of life is often underestimated. The prevalence and incidence of gout are increasing globally. Further, ischemic heart disease (IHD) and chronic kidney disease (CKD) are prevalent in gout patients. Some unmet needs for gout management include physicians' low initiation rate of urate-lowering therapy (ULT) and poor treatment adherence in patients with gout. There is also a lack of randomized controlled trials that establish safe doses of acute and long-term treatment for gout, particularly in patients with IHD and stage 4 CKD and above (including end-stage renal failure). Furthermore, there is also a lack of studies showing optimal serum uric acid (SUA) target and validated clinical outcome measures, including disease activity and remission criteria for gout tailored to treat-to-target approaches and the high cost of newer gout medications. The causal relationship between asymptomatic hyperuricemia or gout with comorbidities such as IHD and CKD has yet to be fully elucidated. There is a pressing need for collaborative international efforts to address the overall suboptimal management of gout.

Assessing tophaceous spinal gout treatment response using dual-energy CT as a point-of-care imaging modality: case report

We describe a case of chronic tophaceous gout affecting the spine, hands, elbows, feet, and knees in a 67-year-old man with serum urate levels at 549 µmol/L whose response to treatment was successfully mapped using dual-energy computed tomography (DECT). The patient presented with exacerbation of acute-on-chronic lumbar back pain. He had received a diagnosis of gout 3 years prior to this presentation yet was not on any urate-lowering therapy. The patient received febuxostat 80 mg and colchicine 0.3 mg once daily and underwent DECT to assess baseline monosodium urate (MSU) burden. At baseline, MSU deposits were seen in the hands, elbows, feet, knees, and lumbar spine including the left L5-S1 facet joint encroaching onto the neural foramen. After 2.5 years of treatment, serum urate level was within the target range (< 360 µmol/L), and the patient underwent a follow-up DECT that revealed almost full resolution of MSU deposition in the spine, including the MSU-burdened facet joint and neural foramen in the lumbar spine, in addition to all the affected peripheral joints. This case is the first report of radiological evidence of nearly complete resolution of MSU deposits in spinal gout on DECT after urate-lowering therapy treatment, which demonstrates the utility of this imaging modality as a non-invasive investigational point-of-care imaging modality for mapping treatment response and identifying the etiology of back pain in a patient with chronic tophaceous spinal gout.

Critical appraisal of serum urate targets in the management of gout

Gout management involves two broad aspects: treatment of gout flares to provide rapid symptomatic relief and long-term urate-lowering therapy to lower serum urate sufficiently to prevent gout flares from occurring. All of the major rheumatology societies recommend a target serum urate of <5 mg/dl (<0.30 mmol/l) or <6 mg/dl (<0.36 mmol/l), both of which are below the point of saturation for urate and therefore lead to monosodium urate crystal dissolution. In this Review, we describe the rationale for treat-to-target urate approach in the long-term management of gout and the current evidence and controversy around the appropriate serum urate targets.

A glance into the future of gout

Gout is characterized by monosodium urate (MSU) crystal deposits in and within joints. These deposits result from persistent hyperuricaemia and most typically lead to recurrent acute inflammatory episodes (gout flares). Even though some aspects of gout are well characterized, uncertainties remain; this upcoming decade should provide further insights into many of these uncertainties. Synovial fluid analysis allows for the identification of MSU crystals and unequivocal diagnosis. Non-invasive methods for diagnosis are being explored, such as Raman spectroscopy and imaging modalities. Both ultrasound and dual-energy computed tomography (DECT) allow the detection of MSU crystals; this not only provides a mean of diagnosis, but also has furthered gout knowledge defining the presence of a preclinical deposition in asymptomatic hyperuricaemia. Scientific consensus establishes the beginning of gout as the beginning of symptoms (usually the first flare), but the concept is currently under review. For effective long-term gout management, the main goal is to promote crystal dissolution treatment by reducing serum urate below 6 mg/dL (or 5 mg/dL if faster crystal dissolution is required). Current urate-lowering therapies' (ULTs) options are limited, with allopurinol and febuxostat being widely available, and probenecid, benzbromarone, and pegloticase available in some regions. New xanthine oxidase inhibitors and, especially, uricosurics inhibiting urate transporter URAT1 are under development; it is probable that the new decade will see a welcomed increase in the gout therapeutic armamentarium. Cardiovascular and renal comorbidities are common in gout patients. Studies determining whether optimal treatment of gout will positively impact these comorbidities are currently lacking, but will hopefully be forthcoming. Overall, the single change that will most impact gout management is greater uptake of international rheumatology society recommendations. Innovative strategies, such as nurse-led interventions based on these recommendations have recently demonstrated treatment success for people with gout.

Urate crystal deposition is associated with inflammatory markers and carotid artery pathology in patients with intercritical gout: results from the NOR-Gout study

BACKGROUND

Gout is of unknown reason associated with cardiovascular disease. Ultrasound is sensitive for detecting crystal deposition and plasma calprotectin is a sensitive inflammatory marker. This study explores the associations between crystal deposition, inflammation and carotid artery pathology.

METHOD

A cross-sectional analysis of baseline assessments from the NOR-Gout study was undertaken. Crystal deposition was assessed by ultrasound (double contour, tophi, aggregates) and dual-energy CT (DECT) and laboratory assessments included plasma calprotectin. The carotid arteries were bilaterally examined for carotid intima-media thickness (cIMT) and presence of plaques. Spearman correlations, Mann-Whitney tests and linear regression analyses were used to explore associations between crystal deposition, inflammatory markers,and carotid pathology.

RESULTS

202 patients with intercritical gout (95.5% men, mean (SD) age 56.5 (13.8) years, disease duration 7.9 (7.7) years) were included. Calprotectin was correlated with all scores of crystal deposition by ultrasound (r=0.26-0.32, p<0.001) and DECT (r=0.15, p<0.05). cIMT was correlated with sum score aggregates (r=0.18-0.22, p<0.05). Patients with large tophi had higher levels of calprotectin as well as more frequent carotid plaque (p<0.05).

CONCLUSIONS

Study findings point towards crystal deposition contributing to subclinical inflammation with subsequent vascular implications. However, future longitudinal studies are needed to confirm such causal relationships.

One- and 2-year flare rates after treat-to-target and tight-control therapy of gout: results from the NOR-Gout study

OBJECTIVES

To explore the frequency and predictors of flares over 2 years during a treat-to-target strategy with urate-lowering therapy (ULT) in patients with gout.

METHODS

In the treat-to-target, tight control NOR-Gout study patients started ULT with escalating doses of allopurinol. Flares were recorded over 2 years. Baseline predictors of flares during months 9-12 in year 1 and during year 2 were analyzed by multivariable logistic regression.

RESULTS

Of 211 patients included (mean age 56.4 years, disease duration 7.8 years, 95% males), 81% (150/186) of patients experienced at least one gout flare during the first year and 26% (45/173) during the second year. The highest frequency of flares in the first year was seen during months 3-6 (46.8% of patients). Baseline crystal depositions detected by ultrasound and by dual-energy computed tomography (DECT) were the only variables which predicted flares both during the first period of interest at months 9-12 (OR 1.033; 95% CI 1.010-1.057, and OR 1.056; 95% CI 1.007-1.108) and also in year 2. Baseline subcutaneous tophi (OR 2.42, 95% CI 1.50-5.59) and prior use of colchicine at baseline (OR 2.48, 95% CI 1.28-4.79) were independent predictors of flares during months 9-12, whereas self-efficacy for pain was a protective predictor (OR 0.98 per unit, 95% CI 0.964-0.996).

CONCLUSIONS

In patients with gout, flares remain frequent during the first year of a treat-to-target ULT strategy, especially during months 3-6, but are much less frequent during year 2. Baseline crystal depositions predict flares over 2 years, supporting ULT early during disease course.

TRIAL REGISTRATION

ACTRN12618001372279.

Dual-energy computed tomography in crystalline arthritis: knowns and unknowns

PURPOSE OF REVIEW

To give an overview of what can reasonably be considered as known about dual-energy computed tomography (DECT) in crystal-related arthropathies, and what still needs to be explored.

RECENT FINDINGS

Recent studies suggest an overall superiority of DECT over ultrasound in gout in terms of sensitivity (89 vs. 84%) and specificity (91 vs. 84%), except in early disease. Additional studies are needed to optimize DECT postprocessing settings in order to improve the specificity of the technique and eliminate all artifacts. Evidence has been controversial concerning DECT's ability to detect monosodium urate (MSU) crystal deposits on vessel walls, or whether or not MSU-coded plaques are artifacts. DECT can be used to monitor MSU crystal depletion during urate-lowering treatment; MSU crystal volume is associated with cardiovascular risk and disease activity. There are some reports on calcium-containing crystal deposition diseases (calcium pyrophosphate and basic calcium phosphate) demonstrating that DECT can characterize and discriminate between the different types of crystals.

SUMMARY

Our knowledge about the use of DECT in crystal-related arthropathies continues to expand. Some unknowns have been clarified but there's still lots to learn, particularly concerning gout management and the potential use of DECT in calcium-containing crystal-related arthropathies.

Gouty Arthropathy: Review of Clinical Manifestations and Treatment, with Emphasis on Imaging

Gout, a crystalline arthropathy caused by the deposition of monosodium urate crystals in the articular and periarticular soft tissues, is a frequent cause of painful arthropathy. Imaging has an important role in the initial evaluation as well as the treatment and follow up of gouty arthropathy. The imaging findings of gouty arthropathy on radiography, ultrasonography, computed tomography, dual energy computed tomography, and magnetic resonance imaging are described to include findings of the early, acute and chronic phases of gout. These findings include early monosodium urate deposits, osseous erosions, and tophi, which may involve periarticular tissues, tendons, and bursae. Treatment of gout includes non-steroidal anti-inflammatories, colchicine, glucocorticoids, interleukin-1 inhibitors, xanthine oxidase inhibitors, uricosuric drugs, and recombinant uricase. Imaging is critical in monitoring response to therapy; clinical management can be modulated based on imaging findings. This review article describes the current standard of care in imaging and treatment of gouty arthropathy.