Serum urate as surrogate endpoint for flares in people with gout: A systematic review and meta-regression analysis

Dual-Energy Computed Tomography Applications in Rheumatology

Dual-energy computed tomography (DECT) has emerged as a transformative tool in the past decade. Initially employed in gout within the field of rheumatology to distinguish and quantify monosodium urate crystals through its dual-material discrimination capability, DECT has since broadened its clinical applications. It now encompasses various rheumatic diseases, employing advanced techniques such as bone marrow edema assessment, iodine mapping, and collagen-specific imaging. This review article aims to examine the unique characteristics of DECT, discuss its strengths and limitations, illustrate its applications for accurately evaluating various rheumatic diseases in clinical practice, and propose future directions for DECT in rheumatology.

Associations Between Surrogate Markers and Clinical Outcomes for Nononcologic Chronic Disease Treatments

Importance

Surrogate markers are increasingly used as primary end points in clinical trials supporting drug approvals.

Objective

To systematically summarize the evidence from meta-analyses, systematic reviews and meta-analyses, and pooled analyses (hereafter, meta-analyses) of clinical trials examining the strength of association between treatment effects measured using surrogate markers and clinical outcomes in nononcologic chronic diseases.

Data sources

The Food and Drug Administration (FDA) Adult Surrogate Endpoint Table and MEDLINE from inception to March 19, 2023.

Study Selection

Three reviewers selected meta-analyses of clinical trials; meta-analyses of observational studies were excluded.

Data Extraction and Synthesis

Two reviewers extracted correlation coefficients, coefficients of determination, slopes, effect estimates, or results from meta-regression analyses between surrogate markers and clinical outcomes.

Main Outcomes and Measures

Correlation coefficient or coefficient of determination, when reported, was classified as high strength (r ≥ 0.85 or R2 ≥ 0.72); primary findings were otherwise summarized.

Results

Thirty-seven surrogate markers listed in FDA's table and used as primary end points in clinical trials across 32 unique nononcologic chronic diseases were included. For 22 (59%) surrogate markers (21 chronic diseases), no eligible meta-analysis was identified. For 15 (41%) surrogate markers (14 chronic diseases), at least 1 meta-analysis was identified, 54 in total (median per surrogate marker, 2.5; IQR, 1.3-6.0); among these, median number of trials and patients meta-analyzed was 18.5 (IQR, 12.0-43.0) and 90 056 (IQR, 20 109-170 014), respectively. The 54 meta-analyses reported 109 unique surrogate marker-clinical outcome pairs: 59 (54%) reported at least 1 r or R2, 10 (17%) of which reported at least 1 classified as high strength, whereas 50 (46%) reported slopes, effect estimates, or results of meta-regression analyses only, 26 (52%) of which reported at least 1 statistically significant result.

Conclusions and Relevance

Most surrogate markers used as primary end points in clinical trials to support FDA approval of drugs treating nononcologic chronic diseases lacked high-strength evidence of associations with clinical outcomes from published meta-analyses.

Serum Urate Monitoring Among Older Adults With Gout: Initiating Urate-Lowering Therapy in Ontario, Canada

OBJECTIVE

To assess the proportion of, and factors associated with, older adults with gout receiving a serum urate (SUA) test after starting urate-lowering therapy (ULT).

METHODS

We performed a population-based retrospective cohort study in Ontario, Canada in patients ages ≥66 years with gout, newly dispensed ULT between 2010 and 2019. We characterized patients with SUA testing within 6 and 12 months after ULT dispensation. Multilevel logistic regression clustered by ULT prescriber evaluated the factors associated with SUA monitoring within 6 months.

RESULTS

We included 44,438 patients with a mean ± SD age of 76.0 ± 7.3 years and 64.4% male. Family physicians prescribed 79.1% of all ULTs. SUA testing was lowest in 2010 (56.4% at 6 months) and rose over time to 71.3% in 2019 (P < 0.0001). Compared with rheumatologists, family physicians (odds ratio [OR] 0.26 [95% confidence interval (95% CI) 0.23-0.29]), internists (OR 0.34 [95% CI 0.29-0.39]), nephrologists (OR 0.37 [95% CI 0.30-0.45]), and other specialties (OR 0.25 [95% CI 0.21-0.29]) were less likely to test SUA, as were male physicians (OR 0.87 [95% CI 0.83-0.91]). Patient factors associated with lower odds of SUA monitoring included rural residence (OR 0.81 [95% CI 0.77-0.86]), lower socioeconomic status (OR 0.91 [95% CI 0.85-0.97]), and patient comorbidities. Chronic kidney disease, hypertension, diabetes mellitus, and coprescription of colchicine/oral corticosteroids (OR 1.31 [95% CI 1.23-1.40]) were correlated with increased SUA testing.

CONCLUSION

SUA testing is suboptimal among older adults with gout initiating ULT but is improving over time. ULT prescriber, patient, and prescription characteristics were correlated with SUA testing.

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.

Exploring the Multifaceted Nexus of Uric Acid and Health: A Review of Recent Studies on Diverse Diseases

The prevalence of patients with hyperuricemia or gout is increasing worldwide. Hyperuricemia and gout are primarily attributed to genetic factors, along with lifestyle factors like consuming a purine-rich diet, alcohol and/or fructose intake, and physical activity. While numerous studies have reported various comorbidities linked to hyperuricemia or gout, the range of these associations is extensive. This review article focuses on the relationship between uric acid and thirteen specific domains: transporters, genetic factors, diet, lifestyle, gout, diabetes mellitus, metabolic syndrome, atherosclerosis, hypertension, kidney diseases, cardiovascular diseases, neurological diseases, and malignancies. The present article provides a comprehensive review of recent developments in these areas, compiled by experts from the Young Committee of the Japanese Society of Gout and Uric and Nucleic Acids. The consolidated summary serves to enhance the global comprehension of uric acid-related matters.

Ultrasonography in the prediction of gout flares: a 12-month prospective observational study

OBJECTIVES

To evaluate whether US findings indicating MSU deposits and US-detected inflammation (i.e. power Doppler signal) predict gout flares over 12 months.

METHODS

Gout patients on urate-lowering therapy for at least the preceding 6 months were enrolled consecutively in this 12-month prospective, observational, single-centre study. A nested case-control analysis was performed. Cases were participants with at least one flare in the follow-up period, while controls did not self-report any gout flare. The US assessment included elbows, wrists, second MCP joints, knees, ankles, and first MTP joints. The US findings indicating MSU deposits [i.e. aggregates, double contour (DC) sign and tophi] were identified as present/absent according to the Outcome Measure in Rheumatology definitions. Power Doppler signal was scored semiquantitatively. Summated scores were calculated for each US finding.

RESULTS

Eighty-one gout participants were enrolled, and 71 completed the study. Thirty (42.3%) of 71 participants experienced at least one flare over 12 months, with a median of 2.0 flares. Cases had a greater US burden of MSU deposits (6.7 ± 4.7 vs 2.9 ± 2.6, P = 0.01) and power Doppler signal (3.73 ± 3.53 vs 0.82 ± 1.44, P < 0.01) than controls, at baseline. The baseline US scores indicating MSU deposits and US-detected inflammation were significantly associated with the occurrence (total MSU score, adjusted odds ratio:1.75, 95% CI: 1.26, 2.43; power Doppler score, adjusted odds ratio: 1.63, 95% CI: 1.12, 2.40) and the number (total MSU score, adjusted incidence risk ratio: 1.17, 95% CI: 1.08, 1.26; power Doppler score, adjusted incidence risk ratio: 1.29, 95% CI: 1.19, 1.40) of flares over 12 months in multivariate analyses.

CONCLUSIONS

Baseline US findings indicating MSU deposits and US-detected inflammation are independent predictors of gout flares over 12 months.

Fluctuation and change of serum urate levels and flares in gout: results from the NOR-Gout study

A gout attack may evolve after a purine-rich diet or alcohol and after starting urate-lowering therapy (ULT). The relationships between fluctuation and change in serum urate (SU) with the occurrence of flares were investigated in this study. In the prospective NOR-Gout study, gout patients with increased SU and a recent flare were treated to target with ULT over 1 year, with follow-up at year 2 with SU and flare as outcomes. SU and flares were assessed at both monthly and 3-monthly intervals until target SU was reached. Fluctuation over periods and changes in SU between two time points were assessed and compared in patients with and without flares. At year 1, 186 patients completed follow-up (88.2%) and 173 (82.0%) at year 2. Mean age (SD) at baseline was 56.4 (13.7) years, disease duration was 7.8 (7.6) years, and 95.3% were men. The first-year SU fluctuation and change were related to flare occurrence during year 1 (both p < 0.05). High fluctuation with an absolute sum of all SU changes during the first 9 months was related to flares over 3-month periods (all p < 0.05), and high fluctuation during the first 3 months was related to flares in months 3-6 (p = 0.04). Monthly and high SU changes or again reaching higher SU levels > 360 µmol/l were not related to flares. Fluctuation and change in SU were related to flare occurrence during the first year of ULT, while changes between visits and reaching SU levels > 360 µmol/L were not related to flares. Key Points • Urate-lowering therapy seeks to achieve a treatment target and prevent gout flares, and changes in serum urate are related to gout flares. • Fluctuation and changes in serum urate were associated with gout flares, suggesting that fluctuation in serum urate is unfavourable during gout treatment. • During urate-lowering therapy in gout in clinical practice, fluctuation of serum urate, for example, due to lack of adherence, should be observed and avoided.

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.

When underlying biology threatens the randomization principle - initial gout flares of urate-lowering therapy

Flare is the dominant feature of gout and occurs because of inflammatory response to monosodium urate crystals; prevention of gout flares should be the major goal of gout care. However, a paradoxical increase in the risk of flare following initiation of urate-lowering therapy presents considerable challenges for proving the expected long-term benefits of flare prevention in clinical trials. Nevertheless, excluding from enumeration flares that occur in the initial post-randomization period (which can last several months to 1 year) can threaten the core benefits of randomization: the characteristics of the remaining participants can differ from those who were randomized, introducing potential bias from confounding (both measured and unmeasured); participants who drop out or die are excluded from the analysis, introducing potential selection bias; and, finally, ignoring initial flares underestimates participants’ experience during the trial. This Perspective discusses these issues and recommends measures that will allow for high-level evidence that preserves the randomization principle, to satisfy methodological scrutiny and generate robust evidence-based guidelines for gout care.

The paradoxical increase in gout flare risk upon initiation of urate-lowering therapy presents challenges for the measurement and analysis of gout flares in clinical trials of urate-lowering therapy. In this Perspective, the authors highlight these issues and discuss potential solutions.

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.

The Role of Advanced Imaging in Gout Management

Gout is a common form of inflammatory arthritis where urate crystals deposit in joints and surrounding tissues. With the high prevalence of gout, the standardized and effective treatment of gout is very important, but the long-term treatment effect of gout is not satisfied because of the poor adherence in patients to the medicines. Recently, advanced imaging modalities, including ultrasonography (US), dual-energy computed tomography (DECT), and magnetic resonance imaging (MRI), attracted more and more attention for their role on gout as intuitive and non-invasive tools for early gout diagnosis and evaluation of therapeutic effect. This review summarized the role of US, DECT, and MRI in the management of gout from four perspectives: hyperuricemia, gout attacks, chronic gout, and gout complications described the scoring systems currently used to quantify disease severity and discussed the challenges and limitations of using these imaging tools to assess response to the gout treatment.

Effect of Clinical Typing on Serum Urate Targets of Benzbromarone in Chinese Gout Patients: A Prospective Cohort Study

Introduction

Achieving a goal of serum urate levels in patients with gout is an important way to prevent gout and its complications while it remains difficult with a low targeting rate worldwidely. Currently, hyperuricemia classification has not been widely applied to the management of gout owing to insufficient clinical evidences. This study aimed to evaluate the effectiveness of achieving target urate based on hyperuricemia classification in Chinese patients with gout.

Methods

In this prospective study, patients with gout receiving urate lowering therapy with benzbromarone were assigned to two groups, a renal underexcretion and an unclassified type. The primary endpoint was the proportion of patients achieving the serum urate target (<360 μmol/L) during the 12-week study. The frequency of acute gout attacks as well as physical and chemical indicators were secondary endpoints.

Results

Target serum urate level was achieved in 60.5% of underexcretors compared with 39.0% of patients of the unclassified type at week 12 (P = 0.002). Blood glucose and cholesterol levels were lower in the underexcretor group compared with the unclassified type group at the end of the trial, without significant different frequencies in gout flare during the study. In subgroup analysis, stratified by body mass index and estimated glomerular filtration rate, the proportion of patients with serum urate <360 μmol/L was greater in the underexcretion compared with the unclassified type group.

Conclusions

The increased achievement of target serum urate in the underexcretion group supports the use of a clinical hyperuricemia typing treatment strategy for gout.

Association between serum urate and flares in people with gout and evidence for surrogate status: a secondary analysis of two randomised controlled trials

BACKGROUND

Use of serum urate as a treatment target and outcome measure has become controversial in view of the 2017 American College of Physicians guidelines, which advocated a treat-to-symptom rather than a treat-to-target serum urate approach to gout management. The relevance of serum urate as a treatment target measure implies that achievement of target serum urate is causally associated with improvement in patient-important outcomes such as reduction in the number of gout flares. The aim of this study was to assess the causal relationship between achieving target serum urate and the occurrence of gout flares.

METHODS

We analysed individual patient-level data from two randomised trials on urate-lowering therapies in people with gout conducted in Nottingham, UK, and New Zealand. We included participants randomly assigned to immediate dose escalation in the New Zealand study and all participants in the Nottingham study (a nurse-led gout care group and a general practitioner-led usual care group). Individuals who on average achieved a serum urate concentration less than 6 mg/dL (0·36 mmol/L) based on data at 6, 9, and 12 months post-baseline were defined as serum urate responders. The primary outcome was the proportion of participants having at least one gout flare, and the secondary outcome was the mean number of flares per participant per month, from 12 to 24 months after baseline, compared between serum urate responders and non-responders. In adjusted logistic regression models, serum urate at baseline, previous flare history (in the year preceding study entry), presence of tophi at baseline, and, for the Nottingham dataset, the original randomisation group, were included as covariates. The Nottingham study was registered with ClinicalTrials.gov, NCT01477346. The New Zealand study was registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000845932.

FINDINGS

From the combined individual data from both trials, we identified 343 serum urate responders and 245 serum urate non-responders. Significantly fewer serum urate responders had a gout flare than did serum urate non-responders between 12 and 24 months (91 [27%] of 343 vs 156 [64%] of 245; adjusted odds ratio [OR] 0·29 [95% CI 0·17 to 0·51], p<0·0001). The mean number of flares per participant per month between 12 and 24 months was significantly lower in serum urate responders than in serum urate non-responders (adjusted mean difference -1·41 [95% CI -1·77 to -1·04], p<0·0001). This association was independent of the original randomised treatment allocation.

INTERPRETATION

Achieving an average serum urate concentration less than 6 mg/dL is associated with an absence of gout flares and a reduction in the number of flares in the subsequent 12 months in people with gout. These results support a treat-to-target serum urate approach in the management of gout.

FUNDING

None.

Serum urate as a proposed surrogate outcome measure in gout trials: From the OMERACT working group

Serum urate (SU) is the most common primary efficacy outcome in trials of urate-lowering therapies for gout. Despite this, it is not formally considered a validated surrogate outcome. In this paper we will outline the definitions of biomarkers and surrogate outcome measures, respectively as well as the available frameworks and challenges in the assessment of the validity of serum urate as a surrogate in gout (i.e. a reasonable replacement for gout symptoms).

Treatment advances in gout

The purpose of gout treatment is to alleviate symptoms of flares, prevent flares from recurring by lowering serum urate, and minimize structural joint damage and functional impairment. In recent years, several new medications to treat gout have been developed, and novel agents continue to be investigated, in addition to several long-established treatments. Although a number of effective therapies are available, optimal management and outcomes are frequently not achieved due to physician under prescribing of urate-lowering therapy (ULT) and poor adherence with therapy when it is prescribed. This article reviews recent developments in the management of gout with reference to recently published clinical guidelines, outlines some important questions regarding the safety and efficacy of particular agents, and remaining gaps in our knowledge about the most effective strategies for using currently available treatments.

Contentious Issues in Gout Management: The Story so Far

Gout is the most common inflammatory arthritis worldwide. Although gout has been known for antiquity, many challenges still exist in gout management. It is vital to view gout as a chronic disease and not just treat the acute flare. There is a perception of gout as an acute disease requiring treatment only for acute flares. However, to combat the disease, chronic urate-lowering therapy, reducing the serum urate levels to below the saturation threshold of 6.8 mg/dL, and chronic anti-inflammatory prophylaxis, especially during urate-lowering therapy initiation, are needed. In this manuscript, we discuss some of the contentious issues in gout management. These include the timing of urate-lowering therapy initiation, which urate-lowering therapy to chose, should comorbidities influence our treatment, using genetic determinants, and patient perspectives to drive treatment and differences between gout treatment the American College of Physicians and Rheumatology guidelines for gout management: driving care.

High Rate of Adherence to Urate-Lowering Treatment in Patients with Gout: Who's to Blame?

Introduction

Gout is commonly associated with low adherence rates, thus limiting the effectiveness of treatment. Nevertheless, informed and empowered patients may be more likely to achieve high adherence. We intend to demonstrate that adherence in clinical practice may reach that achieved in clinical trials.

Methods

This was a transversal study within an inception cohort of patients with gout prospectively followed up. Patients were informed at entrance in the cohort of outcomes, targets, and means to implement for successful treatment. Adherence was evaluated through electronic medication possession ratio (MPR) for urate-lowering medication and oral medications for hypertension, diabetes, and hyperlipidemia for comparison. Factors associated with nonadherence, and the relation between nonadherence and serum urate levels while on treatment were analyzed.

Results

Data were retrieved from 336 patients, who showed a mean MPR of 87.5%, with 82.1% of patients showing MPR ≥ 0.8. Rates of adherence for hypertension, hyperlipidemia, and diabetes were quite similar (88%, 87%, and 83%, respectively), although MPR > 0.8 was significantly lower for oral medications for diabetes. Adherence was lower, but nevertheless quite fair, during the first year of follow-up, and increasing over time. Active follow-up and comorbidity were associated with good adherence, and adherence and long-term follow-up were associated with higher rates of achieving serum urate within therapeutic target.

Conclusion

Patients with gout show high rates of adherence if empowered. Active follow-up and comorbidity are associated with high rates of adherence. Adherence is strongly associated with higher rates of achievement of therapeutic serum urate target.

Linked Pharmacometric-Pharmacoeconomic Modeling and Simulation in Clinical Drug Development

Market access and pricing of pharmaceuticals are increasingly contingent on the ability to demonstrate comparative effectiveness and cost-effectiveness. As such, it is widely recognized that predictions of the economic potential of drug candidates in development could inform decisions across the product life cycle. This may be challenging when safety and efficacy profiles in terms of the relevant clinical outcomes are unknown or highly uncertain early in product development. Linking pharmacometrics and pharmacoeconomics, such that outputs from pharmacometric models serve as inputs to pharmacoeconomic models, may provide a framework for extrapolating from early-phase studies to predict economic outcomes and characterize decision uncertainty. This article reviews the published studies that have implemented this methodology and used simulation to inform drug development decisions and/or to optimize the use of drug treatments. Some of the key practical issues involved in linking pharmacometrics and pharmacoeconomics, including the choice of final outcome measures, methods of incorporating evidence on comparator treatments, approaches to handling multiple intermediate end points, approaches to quantifying uncertainty, and issues of model validation are also discussed. Finally, we have considered the potential barriers that may have limited the adoption of this methodology and suggest that closer alignment between the disciplines of clinical pharmacology, pharmacometrics, and pharmacoeconomics, may help to realize the potential benefits associated with linked pharmacometric-pharmacoeconomic modeling and simulation.

Rapid disappearance of gouty tophi of the foot by resection of massive gouty tophi of the opposite foot in a patient with hyperuricaemia: a case report

Gouty tophi occur less frequently and disappear only with modern medication therapy for symptomatic or asymptomatic hyperuricaemia. However, the medication may require a long time to take effect due to the systemic urate pool associated with massive gouty tophi. We present the case of a 37-year-old woman who suffered from massive gouty tophi of both feet due to hyperuricaemia. After resection of the massive gouty tophi from her right foot and treatment with uricemia medication, the gouty tophi of her opposite foot disappeared rapidly due to reducing the patient's systemic urate pool with intensification of drug medication.

Association of urate deposition shown by ultrasound and frequent gout attacks

BACKGROUND

There are few data demonstrating the association between urate burden assessed by ultrasound (US) and gout flares. The aim of this study was to determine the association of urate deposition shown by US and frequent gout attacks.

MATERIALS AND METHODS

Patients with gout were divided into two groups according to the frequency of gout attacks in the previous 12 months: frequent (>2 attacks) and infrequent (0-2 attacks). Urate deposition in the hands, knees, and feet was assessed by US.

RESULTS

Overall, 106 patients were enrolled in this study, of whom 32 (30.1%) had had frequent gout attacks (>2 attacks) in the previous 12 months (the average number of gout attacks was 4.7, range 3-12). Those with frequent gout attacks had significantly longer gout duration, a higher serum urate level, and more urate deposition shown by US than those with infrequent gout attacks (P < 0.05). In both univariate and logistic regression analyses, frequent gout attacks were correlated with gout duration, serum urate level, and urate deposition as shown by US (P < 0.05).

CONCLUSION

These findings indicate that urate deposition shown by US is independently associated with frequent gout attacks. Special attention should be given to the prevention of flares in patients with an initially high urate burden as assessed by US.

UltraSound evaluation in follow-up of urate-lowering therapy in gout phase 2 (USEFUL-2): Duration of flare prophylaxis

OBJECTIVES

To determine whether changes in ultrasonography (US) features of monosodium urate crystal deposition is associated with the number of gouty flares after stopping gout flare prophylaxis.

METHODS

We performed a 1-year multicentre prospective study including patients with proven gout and US features of gout. The first phase of the study was a 6-month US follow-up after starting urate-lowering therapy (ULT) with gout flare prophylaxis. After 6 months of ULT, gout flare prophylaxis was stopped, followed by a clinical follow-up (M6 to 12) and ULT was maintained. Outcomes were the proportion of relapsing patients between M6 and M12 according to changes of US features of gout and determining a threshold decrease in tophus size according to the probability of relapse.

RESULTS

We included 79 gouty patients [mean (±SD) age 61.8±14 years, 91% males, median disease duration 4 (IQR 1.5;10) years]. Among the 49 completers at M12, 23 (47%) experienced relapse. Decrease in tophus size ≥50% at M6 was more frequent without than with relapse (54% vs. 26%, P=0.049). On ROC curve analysis, a threshold decrease of 50.8% in tophus size had the best sensitivity/specificity ratio to predict relapse [AUC 0.649 (95% confidence interval 0.488; 0.809)]. Probability of relapse was increased for patients with a decrease in tophus size <50% between M0 and M6 [OR 3.35 (95% confidence interval 0.98; 11.44)].

CONCLUSION

A high reduction in US tophus size is associated with lower probability of relapse after stopping gout prophylaxis. US follow-up may be useful for managing ULT and gout flare prophylaxis.

Debates in gout management

PURPOSE OF REVIEW

This review discusses the findings of recently published translational research studies that have the potential to directly impact on the management of gout patients.

RECENT FINDINGS

Recent research suggests that treat-to-target urate-lowering treatment (ULT) alongside individualized education about gout, and shared decision making results in excellent adherence with ULT and prevents gout flares in the long term. Such interventions should preferentially be delivered face-to-face rather than remotely. The recently published CARES study raises the possibility that febuxostat increases the risk of death in people with preexisting major cardiovascular diseases, and, allopurinol should remain the first-choice ULT. There is paucity of data on the dosing of ULT for managing hyperuricaemia in gout patients with chronic kidney disease. However, recent research suggests that the dose of allopurinol can be gradually increased to above the conventional renal dose in people with chronic kidney disease without allopurinol hypersensitivity syndrome. However, additional larger studies are needed in this field.

SUMMARY

In summary, long-term treat-to-target ULT prevents gout flares and improves quality of life. Given the recent safety concerns, gradually up-titrated allopurinol remains the first-line urate-lowering drug.

The burden of subclinical intra-articular inflammation in gout

OBJECTIVE

To assess the burden of subclinical intra-articular inflammation using ultrasound in people with gout.

METHODS

A pilot, prospective longitudinal cohort of 28 participants with gout were examined twice, once during a gout flare (n = 25) and then during an inter-critical phase (n = 27). At each visit, a 52 joint count was done followed by ultrasound examination for detection of intra-articular power Doppler (PD) signal. Clinically active joints were defined as tender and swollen. Data was collected on patient reported gout pain - visual analog scale (VAS) (painVAS), physician global VAS (physicianVAS), Health Assessment Questionnaire (HAQ), serum uric acid, erythrocyte sedimentation rate (ESR), and high-sensitivity C-reactive protein (HsCRP).

RESULTS

At the flare visit, participants had a median of 1 clinically active joint (interquartile range [IQR] 1-2), and a median of 5 joints with a PD score ≥ 2 (IQR 4-10, P < .001). At the inter-critical visit, participants reported an median of 0 clinically active joints (IQR 0-0), and a median of 4 joints with a PD score ≥ 2 (IQR 3-7, P < .001). Physician VAS (5.69 vs 3.40, P < .001), painVAS (6 vs 0, P < .001), HAQ (0.75 vs 0.12, P = .032), and ESR (29 vs 13.5 mm/h, P = .02) were higher at the acute visit, but HsCRP levels were similar (8.88 vs 5.15 mg/L, P = .062).

CONCLUSION

This pilot study established the presence of subclinical intra-articular inflammation in gout at both acute and inter-critical phases. Despite the apparent resolution of symptoms after an acute flare, a relatively high proportion of joints had subclinical inflammation in the inter-critical visit. The long-term implications of untreated subclinical joint inflammation are not clear.

Gout - An update of aetiology, genetics, co-morbidities and management

Gout is an increasingly common chronic disorder of urate crystal deposition that manifests as flares of acute inflammatory arthritis. Hyperuricaemia is a prerequisite and a fifth of both men and woman are hyperuricaemic. The prevalence of gout is much lower than the prevalence of hyperuricaemia for reasons that are not currently clear. Gout is more common in men than women prior to menopause due to the uricosuric effects of oestrogen, but after menopause the incidence of gout rises substantially in women. Co-morbidities are an important issue in gout, with cardiovascular disease, diabetes mellitus, obesity and chronic kidney disease all common in patients with gout. Environmental factors like diet affect the incidence of gout but there is little evidence to support an emphasis on diet in treating established gout. The diagnosis of gout is often made without the use of joint aspiration and validated diagnostic rules are available for both primary and secondary care as well as classification criteria for research use. The overarching principle of the management of gout with pharmacotherapy is the need to reduce serum urate levels to below a target of 0.30 mmol/L or 0.36 mmol/L depending on whether it is tophaceous or non-tophaceous respectively. The use of allopurinol has been researched extensively and newer strategies for safer effective dosing are now recommended. Newer agents have been introduced for the treatment of gout, including febuxostat and lesinurad. A number of important questions in the field are under current investigation.

Monosodium urate burden assessed with dual-energy computed tomography predicts the risk of flares in gout: a 12-month observational study : MSU burden and risk of gout flare

Background

Predicting the risk of flares in patients with gout is a challenge and the link between urate burden and the risk of gout flare is unclear. The objective of this study was to determine if the extent of monosodium urate (MSU) burden measured with dual-energy computed tomography (DECT) and ultrasonography (US) is predictive of the risk of gout flares.

Methods

This prospective observational study recruited patients with gout to undergo MSU burden assessment with DECT (volume of deposits) and US (double contour sign) scans of the knees and feet. Patients attended follow-up visits at 3, 6 and 12 months. Patients having presented with at least one flare at 6 months were compared to those who did not flare. Odds ratios (ORs) (95% confidence interval) for the risk of flare were calculated.

Results

Overall, 64/78 patients included attended at least one follow-up visit. In bivariate analysis, the number of joints with the double contour sign was not associated with the risk of flare (p = 0.67). Multivariate analysis retained a unique variable: DECT MSU volume of the feet. For each 1 cm³ increase in DECT MSU volume in foot deposits, the risk of flare increased 2.03-fold during the first 6 months after initial assessment (OR 2.03 (1.15–4.38)). The threshold volume best discriminating patients with and without flare was 0.81 cm³ (specificity 61%, sensitivity 77%).

Conclusions

This is the first study showing that the extent of MSU burden measured with DECT but not US is predictive of the risk of flares.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1714-9) contains supplementary material, which is available to authorized users.