Presence of monosodium urate crystal deposition by dual-energy CT in patients with gout treated with allopurinol

Baseline Dual-Energy Computed Tomography Urate Volume Predicts Fulfillment of Gout Remission After Two Years of Urate-Lowering Therapy

OBJECTIVE

This study aimed to identify variables that predict gout remission in people with erosive gout receiving urate-lowering therapy.

METHODS

We analyzed data from a two-year, double-masked randomized-controlled trial of people with erosive gout, randomized to a serum urate target of <0.20 mmol/L or <0.30 mmol/L using oral urate-lowering therapies. All participants had dual-energy computed tomography (DECT) scans of the feet and ankles at baseline. The proportion of participants achieving gout remission according to the 2016 preliminary gout remission criteria and simplified gout remission criteria (without the patient reported outcomes) was analyzed. Logistic regression models were used to evaluate predictors of gout remission in year 2.

RESULTS

The preliminary gout remission criteria were fulfilled in 11 of 97 participants (11%) at year 1 and 21 of 92 participants (23%) at year 2. The simplified criteria were fulfilled in 26 of 97 participants (27%) in year 1 and 40 of 92 participants (44%) in year 2. In multivariable regression models, baseline DECT monosodium urate crystal volume was the only significant independent predictor of gout remission at year 2, using either criteria. Each 1-cm3 increase in the baseline DECT monosodium urate crystal volume decreased the odds of fulfilling the 2016 preliminary gout remission criteria (odds ratio [OR] 0.65, 95% confidence interval [CI] 0.46-0.93; P = 0.02) and the simplified gout remission criteria (OR 0.57, 95% CI 0.41-0.78; P < 0.001).

CONCLUSION

In people with erosive gout on urate-lowering therapy, higher baseline DECT monosodium urate crystal volume is associated with lower odds of gout remission after two years of treatment, defined by either the preliminary gout remission criteria or simplified gout remission criteria.

Updates on the Applications of Spectral Computed Tomography for Musculoskeletal Imaging

Spectral CT represents a novel imaging approach that can noninvasively visualize, quantify, and characterize many musculoskeletal pathologies. This modality has revolutionized the field of radiology by capturing CT attenuation data across multiple energy levels and offering superior tissue characterization while potentially minimizing radiation exposure compared to traditional enhanced CT scans. Despite MRI being the preferred imaging method for many musculoskeletal conditions, it is not viable for some patients. Moreover, this technique is time-consuming, costly, and has limited availability in many healthcare settings. Thus, spectral CT has a considerable role in improving the diagnosis, characterization, and treatment of gout, inflammatory arthropathies, degenerative disc disease, osteoporosis, occult fractures, malignancies, ligamentous injuries, and other bone-marrow pathologies. This comprehensive review will delve into the diverse capabilities of dual-energy CT, a subset of spectral CT, in addressing these musculoskeletal conditions and explore potential future avenues for its integration into clinical practice.

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.

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.

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.

Gout of feet and ankles in different stages: The potentiality of a new semiquantitative DECT scoring system in monitoring urate deposition

The purpose of this study was to investigate the diagnostic performance of a novel semi-quantitative dual-energy computed tomography (DECT) scoring system in monitoring urate deposition. This study included 287 patients with gout. All patients underwent ankle/foot DECT scans. DECT scores at different stages were compared and their diagnostic efficacies evaluated. Associations between DECT scores and clinical variables were evaluated. Gouts with positive DECT results in early, middle, and late stages were 78.5 %, 81.4 %, and 95.8 %, respectively (all P > .05). The total and ankle/midfoot DECT scores at different stages significantly increased with disease duration (all P < .05). DECT scores of 4 regions excluding the first metatarsophalangeal joint in early and middle stages were lower than those in late stage (all P < .05). DECT scores achieved excellent diagnostic performance for differentiating gout in early stage from middle and late stages (area under the curve, 0.923 and 0.949), with high sensitivity, specificity, positive predictive value, and negative predictive value (all > 85 %). Total DECT score was highly positively correlated with the volume of urate crystals (R = 0.873, P < .001). Disease duration, serum uric acid level, bone erosion, and Achilles tendon involvement significantly affected total DECT scores (all P < .01). In conclusion, longer disease duration, higher serum uric acid levels, bone erosion, and Achilles tendon involvement were closely associated with total DECT scores. DECT scoring system may be an invaluable tool for gout diagnosis owing to its high detection efficacy and a surrogate method to evaluate the amount of urate crystals and erosion of surrounding tissues.

Predictors of Patient and Physician Assessments of Gout Control

OBJECTIVE

To understand the clinical variables that contribute to the patient and physician assessments of gout control and which variables predict discordant assessments.

METHODS

Patients (n = 223) with gout taking allopurinol ≥300 mg daily attended a standardized gout assessment visit. Participants and physicians completed questionnaires rating their assessment of current gout control using a numerical rating scale (0 = not at all controlled, 10 = fully controlled). Discordance between patients' and physicians' scores was defined as an absolute difference of >2 units.

RESULTS

The mean ± SD patient gout control score was 8.09 ± 2.24, and the physician gout control score was 7.38 ± 2.63 (P < 0.001 for comparison). Absence of gout flares in the last 12 months and in the last 3 months and serum urate at the treatment target (<6 mg/dl) were associated with higher patient and physician gout control scores. Absence of tophus also predicted higher physician, but not patient, gout control scores. Discordant scores for gout control were present in 50 participants (22.3%), mostly due to lower assessment of disease control by physicians. Gout flare in the preceding 3 months (odds ratio [OR] 5.9, P < 0.001) and tophus (OR 3.1, P = 0.007) predicted discordant disease-control assessments in which physicians scored lower gout control than patients.

CONCLUSION

For both patients and physicians, absence of gout flares and serum urate levels at the treatment target predict assessment of gout control. However, discordance between patients and physicians in their assessment of disease control is not uncommon, with recent gout flares and tophus predicting lower scores by physicians than patients.

A multicentre, efficacy and safety study of methotrexate to increase response rates in patients with uncontrolled gout receiving pegloticase (MIRROR): 12-month efficacy, safety, immunogenicity, and pharmacokinetic findings during long-term extension of an open-label study

Background

Publications suggest immunomodulation co-therapy improves responder rates in uncontrolled/refractory gout patients undergoing pegloticase treatment. The MIRROR open-label trial showed a 6-month pegloticase + methotrexate co-therapy responder rate of 79%, compared to an established 42% pegloticase monotherapy responder rate. Longer-term efficacy/safety data are presented here.

Methods

Uncontrolled gout patients (serum urate [SU] ≥ 6 mg/dL and SU ≥ 6 mg/dL despite urate-lowering therapy [ULT], ULT intolerance, or functionally-limiting tophi) were included. Patients with immunocompromised status, G6PD deficiency, severe kidney disease, or methotrexate contraindication were excluded. Oral methotrexate (15 mg/week) and folic acid (1 mg/day) were administered 4 weeks before and during pegloticase therapy. Twelve-month responder rate (SU < 6 mg/dL for ≥ 80% during month 12), 52-week change from baseline in SU, and extended safety were examined. Efficacy analyses were performed for patients receiving ≥ 1 pegloticase infusion. Pharmacokinetics (PK)/anti-drug antibodies (ADAs) were examined and related to efficacy/safety findings.

Results

Fourteen patients were included (all male, 49.3 ± 8.7 years, 13.8 ± 7.4-year gout history, pre-therapy SU 9.2 ± 2.5 mg/dL). Three patients were non-responders and discontinued study treatment before 24 weeks, one patient exited the study per protocol at 24 weeks (enrolled prior to treatment extension amendment), and 10 remained in the study through week 52. Of the 10, 8 completed 52 weeks of pegloticase + methotrexate and were 12-month responders. The remaining two discontinued pegloticase + methotrexate at week 24 (met treatment goals) and stayed in the study under observation (allopurinol prescribed at physicians’ discretion); one remained a responder at 12 months. At 52 weeks, change from baseline in SU was − 8.2 ± 4.1 mg/dL (SU 1.1 ± 2.4 mg/dL, n = 10). Gout flares were common early in treatment but progressively decreased while on therapy (weeks 1–12, 13/14 [92.9%]; weeks 36–52, 2/8 [25.0%]). One patient recovered from sepsis (serious AE). Two non-responders developed high ADA titers; fewer patients had trough concentrations (C_min) below the quantitation limit (BQL), and the median C_min was higher (1.03 µg/mL vs. BQL) than pegloticase monotherapy trials.

Conclusions

Pegloticase + methotrexate co-therapy was well-tolerated over 12 months, with sustained SU lowering, progressive gout flare reduction, and no new safety concerns. Antibody/PK findings suggest methotrexate attenuates ADA formation, coincident with higher treatment response rates.

Trial registration

ClinicalTrials.gov, NCT03635957. Registered on 17 August 2018.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02865-z.

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.

Expert Opinion on Pegloticase with Concomitant Immunomodulatory Therapy in the Treatment of Uncontrolled Gout to Improve Efficacy, Safety, and Durability of Response

PURPOSE OF REVIEW

Gout is a systemic disease from which some patients develop numerous painful tophi that adversely affect quality of life and functionality. Some patients treated with oral urate-lowering therapy are unable to maintain serum urate levels below 6 mg/dL, and these patients, thus classified as having refractory or uncontrolled gout, often require therapy with pegloticase to reduce symptoms and tophaceous burden. The objective of this expert opinion review is to summarize the available evidence supporting the use of concomitant immunomodulators with pegloticase to prevent development of anti-drug antibodies (ADAs) when treating patients with uncontrolled gout.

RECENT FINDINGS

Emerging evidence suggests that adding an immunomodulator to pegloticase therapy can substantially increase response rates to double those observed in phase 3 randomized controlled trials. The combination of immunomodulation with pegloticase should be considered in routine clinical practice to improve durability of response, efficacy, and safety among patients with uncontrolled gout who otherwise have limited therapeutic options.

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.

Tildrakizumab for treatment of moderate to severe psoriasis: an expert opinion of efficacy, safety, and use in special populations

INTRODUCTION

Tildrakizumab is a monoclonal antibody that targets the p19 subunit of IL-23, a crucial cytokine for Th17 cells. Tildrakizumab has been assessed in several Phase I, II, and III clinical trials and is approved for treatment of adults with moderate to severe plaque psoriasis who are indicated for systemic therapy.

AREAS COVERED

The available evidence on the efficacy, safety, and use of tildrakizumab in special populations was evaluated by 14 experts who critically reviewed the current literature.

EXPERT OPINION

Tildrakizumab has good efficacy that lasts for at least 5 years in patients with moderate to severe psoriasis, and appears to be safe and well tolerated in the long-term with no apparent dose-related differences in adverse events, a low incidence of discontinuation due to adverse events, and no evidence of increased risk of malignancies. The safety and the efficacy of tildrakizumab has also been confirmed in special populations such as those with inflammatory bowel disease, cardiovascular disease, metabolic syndrome, and advanced age. Early intervention with IL-23-inhibitors, such as tildrakizumab, may help to control symptoms and change the long-term course of the disease in patients affected by plaque psoriasis, while improving the quality of life and potentially minimizing the risk of developing comorbidities.

Dual-energy computed tomography vs ultrasound, alone or combined, for the diagnosis of gout: a prospective study of accuracy

OBJECTIVE

To examine the accuracy of dual-energy CT (DECT) vs ultrasound or their combination for the diagnosis of gout.

METHODS

Using prospectively collected data from an outpatient rheumatology clinic at a tertiary-care hospital, we examined the diagnostic accuracy of either modality alone or their combination, by anatomical site (feet/ankles and/or knees), for the diagnosis of gout. We used two standards: (i) demonstration of monosodium urate crystals in synovial fluid (gold), and (ii) modified (excluding DECT and ultrasound) 2015 ACR-EULAR gout classification criteria (silver).

RESULTS

Of the 147 patients who provided data, 48 (33%) had synovial fluid analysis performed (38 were monosodium urate-crystal positive) and mean symptom duration was 9.2 years. One hundred (68%) patients met the silver standard. Compared with the gold standard, diagnostic accuracy statistics for feet/ankles DECT, feet/ankles ultrasound, knees DECT and knees ultrasound were, respectively: sensitivity: 87%, 84%, 91% and 58%; specificity: 100%, 60%, 87% and 80%; positive predictive value: 100%, 89%, 97% and 92%; negative predictive value: 67%, 50%, 70% and 33%; area under the receiver operating characteristic curve: 0.93, 0.72, 0.89 and 0.66. Combining feet/ankles DECT with ultrasound or knees DECT with ultrasound led to a numerically higher sensitivity compared with DECT alone, but overall accuracy was lower. Similarly, combining imaging knees to feet/ankles also yielded a numerically higher sensitivity and negative predictive values compared with feet/ankles DECT alone, without differences in overall accuracy. Findings were replicated compared with the silver standard, but with lower numbers.

CONCLUSIONS

Feet/ankles or knees DECT alone had the best overall accuracy for gout diagnosis. The DECT-US combination or multiple joint imaging offered no additional increase in overall diagnostic accuracy.

Limitations of dual-energy CT in the detection of monosodium urate deposition in dense liquid tophi and calcified tophi

OBJECTIVE

Dual-energy CT (DECT) detection of monosodium urate (MSU) crystal deposition has demonstrated good sensitivity and specificity in patients with established gout. However, limitations have been reported with early disease and with low urate burden. We aimed to study the performance of DECT in the detection and quantification of MSU deposition in solid and liquid tophi.

MATERIALS AND METHODS

Patient-derived solid and liquid tophi, suspensions of commercial synthetic, and in-house synthetic MSU crystals were prepared at varying concentrations. DECT was performed at 80 kVp and 150 kVp, and post-processed using Syngo Via gout software (Siemens) that color-coded urate and cortical bone as green and purple, respectively. DECT findings were correlated with ultrasound and microscopic findings. The protocol was reviewed by IRB and considered a non-human subject research.

RESULTS

DECT did not detect urate deposition in either patient-derived liquid tophi or in-house synthetic crystals at any concentration. Lowering the post-processing minimum threshold increased the detection of in-house synthetic crystals but did not change the detection of patient-derived liquid tophi. Areas of calcium-rich purple color-coded regions, masking detection of urate, within the solid tophi and surrounding liquid tophi were noted on DECT. Histology showed co-presence of calcium along with MSU deposition in these.

CONCLUSION

This study illustrates important limitations of DECT for liquid tophi due to subthreshold CT attenuation and for calcified tophi due to the obscuration of urate by calcium. Urate may be either undetectable or underestimated by DECT when these conditions are present.

What is the diagnostic value of dual-energy computed tomography in patients with clinical diagnosis of gout?

OBJECTIVES

To investigate the frequency of monosodium urate (MSU) crystal deposits on dual-energy computed tomography (DECT) in patients with clinical diagnosis of gout and the factors associated MSU crystal positivity.

METHODS

This study was conducted in patients with clinical diagnosis of gout who underwent DECT. Clinical features were compared between patients with positive and those with negative DECT results. A logistic regression analysis was performed to determine the factors associated with MSU crystal positivity on DECT.

RESULTS

A total of 148 patients with clinical diagnosis of gout were included, and MSU crystal deposition on DECT was observed in 64 patients (43.3%). The patients with positive DECT results were more likely to have renal insufficiency, longer disease duration, and higher serum urate level than those with negative. In the multivariable analysis, first gout attack (odds ratio 0.462; 95% confidence interval 0.229-0.931, p = 0.031) was associated with a less likely MSU crystal deposit-positive DECT result. In the subgroup analysis of patients with first attack, serum urate level > 8 mg/dL was associated with DECT positivity.

CONCLUSION

Of the patients with clinical diagnosis of gout, those with renal insufficiency, longer disease duration, and high serum urate level were more likely to be positive of gout on DECT. First gout attack was associated with less likely to be positive for MSU crystal on DECT. Thus, performing DECT scan in the selected patients who had characteristics that highly probability of DECT positivity could increase positive predictive value.

Identification and characterization of peripheral vascular color-coded DECT lesions in gout and non-gout patients: The VASCURATE study

OBJECTIVE

To characterize peripheral vascular plaques color-coded as monosodium urate (MSU) deposition by dual-energy computed tomography (DECT) and assess their association with the overall soft-tissue MSU crystal burden.

METHODS

Patients with suspected crystal arthropathies were prospectively included in the CRYSTALILLE inception cohort to undergo baseline knees and ankles/feet DECT scans; treatment-naive gout patients initiating treat-to-target urate-lowering therapy (ULT) underwent repeated DECT scans with concomitant serum urate level measurements at 6 and 12 months. We determined the prevalence of DECT-based vascular MSU-coded plaques in knee arteries, and assessed their association with the overall DECT volumes of soft-tissue MSU crystal deposition and coexistence of arterial calcifications. DECT attenuation parameters of vascular MSU-coded plaques were compared with dense calcified plaques, control vessels, control soft tissues, and tophi.

RESULTS

We investigated 126 gout patients and 26 controls; 17 ULT-naive gout patients were included in the follow-up study. The prevalence of DECT-based vascular MSU-coded plaques was comparable in gout patients (24.6%) and controls (23.1%; p=0.87). Vascular MSU-coded plaques were strongly associated with coexisting arterial calcifications (p<0.001), but not with soft-tissue MSU deposition. Characterization of vascular MSU-coded plaques revealed specific differences in DECT parameters compared with control vessels, control soft tissues, and tophi. During follow-up, vascular MSU-coded plaques remained stable despite effective ULT (p=0.64), which decreased both serum urate levels and soft-tissue MSU volumes (p<0.001).

CONCLUSION

Our findings suggest that DECT-based MSU-coded plaques in peripheral arteries are strongly associated with calcifications and may not reflect genuine MSU crystal deposition. Such findings should therefore not be a primary target when managing gout patients.

Gout of feet and ankles in different disease durations: diagnostic value of single-source DECT and evaluation of urate deposition with a novel semi-quantitative DECT scoring system

OBJECTIVES

To investigate the diagnostic performance of single-source dual-energy computed tomography (DECT) based on gemstone spectral imaging technology (including Discovery CT750HD and Revolution CT) in patients with suspected feet/ankles gouty arthritis, and evaluate the urate deposition with a novel semi-quantitative DECT scoring system.

METHODS

A total of 196 patients were consecutively included. Feet and ankles were evaluated in all patients by single-source DECT scan. The 2015 EULAR/ACR criteria were used as the reference for the diagnosis of gout. The sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) of DECT for the diagnosis of gout in the early (≤1 year), middle (1-3 years), and late (> 3 years) disease durations were calculated. Besides, a novel semi-quantitative DECT scoring system was assessed for the measurement of urate deposition, and the correlation between the scores and the clinical and serological data were also evaluated. Moreover, the influences of artifacts on the diagnostic performance of DECT were also determined.

RESULTS

The sensitivity, specificity, and AUC of DECT in 196 patients were 38.10, 96.43%, and 0.673 in the early-stage group; 62.96, 100.00%, and 0.815 in the middle-stage group; and 77.55, 87.50%, and 0.825 in the late-stage group, respectively. The overall diagnostic accuracies in the AUC of DECT (Discovery CT750HD and Revolution CT) in the middle and late stages of gout were higher than that in the early stage of gout. Besides, the monosodium urate crystals were deposited on the first metatarsophalangeal joints and ankles/midfeet. Age, the presence of tophus, bone erosion, and disease duration considerably affected the total urate score. No statistical difference in the positive detection of nail artifact, skin artifact, vascular calcification, and noise artifact was found between the case and control groups.

CONCLUSION

DECT (Discovery CT750HD and Revolution CT) showed promising diagnostic accuracy for the detection of urate crystal deposition in gout but had limited diagnostic sensitivity for short-stage gout. Longer disease duration, the presence of tophus, and bone erosion were associated with the urate crystal score system. The artifacts do not remarkably affect the diagnostic performance of DECT in gout.

The inflammatory role of silent urate crystal deposition in intercritical gout

OBJECTIVE

To study subclinical inflammation in intercritical gout patients and its relation to the estimated size of monosodium urate crystal deposition and cardiovascular risk factors.

METHODS

We performed a secretome analysis and the quantification of cytokine and adipokine plasma levels (IL-1β, IL-18, IL-6, sIL-6R, TNFα, CXCL5, RANTES, leptin, resistin and adiponectin) to analize subclinical inflammation in intercritical gout patients. Since it is currently not feasible to determinate the whole body deposit of monosodium urate crystals, we created an indirect clinical classification to estimate it. Then, we compared cytokine levels in controls and gout patients, and in patients with different crystal deposition size. We also studied the association between cytokine-levels and the number of cardiovascular risk factors.

RESULTS

Ninety consecutive patients attending a Crystal Arthritis Unit were studied. IL-18, sIL-6R, RANTES, leptin and adiponectin were higher in intercritical gout patients than in controls. An association was observed between IL-18, sIL6-R and RANTES levels and the size of crystal deposition. IL-18, sIL6-R, RANTES and leptin were higher in patients with no cardiovascular risk factors when compared with controls with no risk factors.

CONCLUSION

Our results showed that the levels of some proinflammatory cytokines and metabolic proteins are elevated in intercritical gout patients. The levels of certain cytokines was related to the estimated size of the monosodium urate crystal deposition and to the number of cardiovascular risk factors. These cytokine changes may help to explain the increase of the cardiovascular events in gout patients.

Crystal deposition measured with dual-energy computed tomography: association with mortality and cardiovascular risks in gout

Objectives

To determine whether the volume of monosodium urate (MSU) crystal deposition measured with dual-energy CT (DECT) is predictive of short-term mortality and development of cardiovascular comorbidities and diabetes mellitus.

Methods

Patients with a diagnosis of gout having had baseline DECT scans of their knees and feet to measure the volume of MSU crystal deposition were included to undergo a follow-up visit. Risk factors for mortality and a composite variable (onset of any cardio-metabolic event) were examined using multivariable Cox models.

Results

A total of 128 patients aged 66.1 (14.0) years with gout durations of 11.4 (10.4) years were included; most were naïve of urate lowering therapy (61.7%), with a follow-up visit at 24 (12, 36) months. Baseline serum urate (SU) level was 7.44 (2.29) mg/dl and DECT volume of MSU crystals was 0.2 (0, 0.9) cm3. A total of 14 patients died during follow-up, 6/14 from a cardiovascular cause, and 17 patients presented a new cardio-metabolic comorbidity. Factors associated with mortality risk were baseline DECT volume of MSU crystals [hazard ratio (HR) 1.02, 95% CI: 1.002, 1.03] and baseline SU level (HR 1.04, 95% CI: 1.003, 1.06). DECT volume of MSU crystals was the only factor associated with the onset of cardio-metabolic comorbidities with a HR of 1.014 (95% CI: 1.001, 1.03).

Conclusions

Volume of MSU crystals measured with DECT is a biomarker for the risk of developing new cardio-metabolic diseases and for all-cause mortality.

Computed tomography in rheumatology - From DECT to high-resolution peripheral quantitative CT

In this chapter, we discuss current updates and applications of Dual Energy Computed Tomography (DECT), iodine-DECT mapping, and high-resolution peripheral quantitative CT (HR-pQCT) in rheumatology. DECT provides a noninvasive diagnosis of gout and can help to differentiate gout from CPPD. Accuracy of DECT varies in various stages of gout. DECT needs specialized hardware, software, and skilled post-processing and interpretation. Sensitivity reduces significantly with deeper tissues such as hip and shoulder. Iodine map enables to delineate inflammatory lesions such as capsulitis and tenosynovitis by improving iodine contrast. Iodine quantification with an iodine map is a promising objective method to evaluate therapeutic effect of inflammatory arthritis. HR-pQCT allows for highly sensitive and specific measures of bone erosions and osteophytes in inflammatory joint diseases, documenting change over time, e.g. in cohorts undergoing immunosuppressive treatments. However, assessing the images requires trained readers, and (semi)-automated scripts to detect bone damage are still undergoing validation and further development.

Volumetric reduction and dissolution prediction of monosodium urate crystal during urate-lowering therapy - a study using dual-energy computed tomography

METHODS

Baseline and follow-up DECTs were performed under a standard ULT protocol. Monthly dissolution rates were calculated by simple and compound methods. Correlations with average SU were compared and analyzed. Best-fit regression model was identified. MSU dissolution times were plotted against SU at different endpoints.

RESULTS

In 29 tophaceous gout patients, MSU volume reduced from baseline 10.94 ± 10.59 cm³ to 2.87 ± 5.27 cm³ on follow-up (p = .00). Dissolution rate had a stronger correlation with SU if calculated by compound method (Pearson's correlation coefficient r= -0.77, p = .00) and was independent of baseline MSU load. The ensuing dissolution model was logarithmic and explained real-life scenarios. When SU > 0.43 mmol/l, dissolution time approached infinity. It improved to 10-19 months at SU = 0.24 mmol/l. When SU approximated zero (as with pegloticase), dissolution flattened and still took 4-8 months.

CONCLUSION

MSU dissolution is better described as a logarithmic function of SU, which explains, predicts, and facilitates understanding of the dissolution process.

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.

Pegloticase in Combination With Methotrexate in Patients With Uncontrolled Gout: A Multicenter, Open-label Study (MIRROR)

OBJECTIVE

To examine the efficacy and safety of pegloticase in combination with methotrexate (MTX) in patients with uncontrolled gout in an exploratory, open-label clinical trial (ClinicalTrials.gov: NCT03635957) prior to a randomized, controlled trial.

METHODS

A multicenter, open-label efficacy and safety study of pegloticase with MTX co-treatment was conducted in patients with uncontrolled gout. Patients were administered oral MTX (15 mg/week) and folic acid (1 mg/day) 4 weeks prior to and throughout pegloticase treatment. The primary study outcome was the proportion of responders, defined as serum uric acid (sUA) < 6 mg/dL for ≥ 80% of the time during Month 6 (Weeks 20, 22, and 24). All analyses were performed on a modified intent-to-treat population, defined as patients who received ≥ 1 pegloticase infusion.

RESULTS

Seventeen patients were screened and 14 patients (all men, average age 49.3 ± 8.7 years) were enrolled. On Day 1, mean sUA was 9.2 ± 2.5 mg/dL, and 12 of the 14 patients had visible tophi. At the 6-month timepoint, 11/14 (78.6%, 95% CI 49.2-95.3%) met the responder definition, with 3 patients discontinuing after meeting protocol-defined treatment discontinuation rules (preinfusion sUA values > 6 mg/dL at 2 consecutive scheduled visits). All patients tolerated MTX. No new safety concerns were identified.

CONCLUSION

In this study, an increased proportion of patients maintained therapeutic response at 6 months when treated concomitantly with MTX and pegloticase as compared to the previously reported 42% using pegloticase alone. These results support the need for a randomized study of MTX or placebo with pegloticase to validate these open-label findings.

Dual energy CT in clinical routine: how it works and how it adds value

Dual energy computed tomography (DECT), also known as spectral CT, refers to advanced CT technology that separately acquires high and low energy X-ray data to enable material characterization applications for substances that exhibit different energy-dependent x-ray absorption behavior. DECT supports a variety of post-processing applications that add value in routine clinical CT imaging, including material selective and virtual non-contrast images using two- and three-material decomposition algorithms, virtual monoenergetic imaging, and other material characterization techniques. Following a review of acquisition and post-processing techniques, we present a case-based approach to highlight the added value of DECT in common clinical scenarios. These scenarios include improved lesion detection, improved lesion characterization, improved ease of interpretation, improved prognostication, inherently more robust imaging protocols to account for unexpected pathology or suboptimal contrast opacification, length of stay reduction, reduced utilization by avoiding unnecessary follow-up examinations, and radiation dose reduction. A brief discussion of post-processing workflow approaches, challenges, and solutions is also included.

P2Y14 receptor has a critical role in acute gouty arthritis by regulating pyroptosis of macrophages

Nod-like receptor protein 3 (NLRP3)-mediated pyroptosis has a causal role in the pathogenesis of gout. P2Y₁₄ receptor (P2Y₁₄R) distributed in immune cells including macrophages is a Gi-coupled receptor that inhibits the synthesis of cAMP, which has been regarded as a potential regulator of inflammatory response. Nevertheless, the role of P2Y₁₄R in MSU-induced pyroptosis of macrophages involved in acute gouty arthritis is still unclear. In our present study, P2Y₁₄R knockout (P2Y₁₄R-KO) disrupted MSU-induced histopathologic changes in rat synoviums, accompanied with a significant inhibition of pyroptotic cell death characterized by Caspase-1/PI double-positive and blockade of NLRP3 inflammasome activation in synovial tissues, which was consistent with that observed in in vitro studies. Owing to the interaction of NLRP3 inflammasome and cAMP, we then investigated the effect of adenylate cyclase activator (Forskolin) on macrophage pyroptosis and gout flare caused by MSU stimulation. The reversal effect of Forskolin verified the negative regulatory role of cAMP in MSU-induced pyroptosis. More importantly, adenylate cyclase inhibitor (SQ22536) intervention led to a reversal of protection attributed to P2Y₁₄R deficiency. Findings in air pouch animal models also verified aforementioned experimental results. Our study first identified the role of P2Y₁₄R/cAMP/NLRP3 signaling pathway in acute gouty arthritis, which provides a novel insight into the pathological mechanisms of pyroptosis-related diseases.

2020 recommendations from the French Society of Rheumatology for the management of gout: Urate-lowering therapy

OBJECTIVE

To develop French Society of Rheumatology-endorsed recommendations for the management of urate-lowering therapy (ULT).

METHODS

Evidence-based recommendations were developed by 9 rheumatologists (academic or community-based), 3 general practitioners, 1 cardiologist, 1 nephrologist and 1 patient, using a systematic literature search, one physical meeting to draft recommendations and two Delphi rounds to finalize them.

RESULTS

A set of 3 overarching principles and 5 recommendations was elaborated. The overarching principles emphasize the importance of patient education, especially the need for explaining the objective of lowering serum urate (SU) level to obtain crystal dissolution, clinical symptoms disappearance and avoidance of complications. ULT is indicated as soon as the diagnosis of gout is established. SU level must be decreased below 300μmol/l (50mg/l) in all gout patients or at least below 360μmol/l (60ml/l) when the 300μmol/l target cannot be reached, and must be maintained at these targets and monitored life-long. The choice of the ULT primarily relies on renal function: in patients whose estimated glomerular filtration rate (eGFR) is above 60ml/min/1.73m², first-line ULT is allopurinol; in those with eGFR between 30 and 60ml/min/1.73m², allopurinol use must be cautious and febuxostat can be considered as an alternative; and in those whose eGFR is below 30ml/min/1.73m², allopurinol must be avoided and febuxostat should be preferred. Prophylaxis of ULT-induced gout flares involves progressive increase of ULT dosage and low-dose colchicine for at least 6 months. Cardiovascular risk factors and diseases, the metabolic syndrome and chronic kidney disease must be screened and managed.

CONCLUSION

These recommendations aim to provide simple and clear guidance for the management of ULT in France.

Utility of Ultrasound and Dual Energy CT in Crystal Disease Diagnosis and Management

PURPOSE OF REVIEW

The objective of this review is to critically discuss the latest evidence on the use of ultrasound and dual energy computed tomography (DECT) for the assessment of microcrystalline arthritis.

RECENT FINDINGS

Both techniques have been included in the classification and diagnostic criteria for gout, while only ultrasound appears in the diagnostic recommendations for CPPD. Regarding the management of the diseases, there is encouraging evidence for the use of both techniques for the follow-up of gout patients, while very few or null data are available for CPPD. Ultrasound has been adequately validated for the diagnosis of CPPD, while some issues have still to be clarified regarding gout. DECT has also demonstrated to be accurate for gout diagnosis, but very few data are available regarding CPPD. Future research should aim to improve the reliability of both techniques and to create scoring systems for a more accurate follow-up of patients.

Dual energy CT findings in gout with rapid kilovoltage-switching source with gemstone scintillator detector

Background

A definite diagnosis of gout requires demonstration of monosodium urate crystals in synovial fluid or in tophi, which in clinical practice today seldom is done. Dual energy CT (DECT) has repeatedly been shown to be able to detect monosodium urate crystals in tissues, hence being an alternative method to synovial fluid microscopy. The vast majority of these studies were performed with CT scanners with two X-ray tubes. In the present study we aim to investigate if and at what locations DECT with rapid kilovoltage-switching source with gemstone scintillator detector (GSI) can identify MSU crystals in patients with clinically diagnosed gout. We also performed a reliability study between two independent readings.

Methods

Patients with new or established gout who had been examined with DECT GSI scanning of the feet at Sahlgrenska University Hospital, Mölndal between 2015 and 2018 were identified. Their medical records were sought for gout disease characteristics using a structured protocol. Urate deposits in MTP1, MTP 2–5, ankle/midfoot joints and tendons were scored semiquantatively in both feet and presence of artifacts in nail and skin as well as beam hardening and noise were recorded. Two radiologists performed two combined readings and scoring of the images, thus consensus was reached over the scoring at each occasion (Espeland et al., BMC Med Imaging. 2013;13:4). The two readings were compared with kappa statistics.

Results

DECT GSI could identify urate deposits in the feet of all 55 participants with gout. Deposits were identified in the MTP-joints of all subjects but were also present in ankle/midfoot joints and tendons in 96 and 75% respectively. Deposition of urate was predicted by longer disease duration (Spearman’s Rho 0.64, p < .0001) and presence of tophi (p = 0.0005). Artifacts were common and mostly found in the nails (73%), a minority displayed skin artifacts (31%) while beam hardening and noise was rare. The agreement between the two readings was good (Κ = 0.66, 95% CI = 0.61–0.71).

Conclusion

The validity of DECT GSI in gout is supported by the identification of urate in all patients with clinical gout and the good correlations with clinical characteristics. The occurrence of artifacts was relatively low with expected locations.

Effects of Conventional Uric Acid-Lowering Therapy on Monosodium Urate Crystal Deposits

OBJECTIVE

Few studies have systematically and quantitatively addressed the impact of urate-lowering therapy on monosodium urate (MSU) deposits. This study was undertaken to analyze the effect of lifestyle measures and conventional urate-lowering therapy on MSU deposits in patients with gout.

METHODS

In this prospective study, subjects with gout according to the American College of Rheumatology/European League Against Rheumatism classification criteria and presence of MSU deposits seen on dual-energy computed tomography (DECT) scans received either lifestyle intervention or conventional urate-lowering therapy for a mean period of 18 months before a follow-up DECT scan. Detected MSU deposits were quantified by volumetric measurement and validated by semiquantitative scoring, and baseline and follow-up measurements were compared.

RESULTS

Baseline and follow-up DECT scans were available for all 83 subjects. Six subjects discontinued treatment, and 77 subjects underwent a lifestyle intervention (n = 24) or were treated with allopurinol (n = 29), febuxostat (n = 22), or benzbromarone (n = 2) over the entire observation period. The mean serum uric acid (UA) level decreased from 7.2 to 5.8 mg/dl in the overall population. In patients who discontinued treatment, no change in MSU deposits or serum UA levels was observed. The burden of MSU deposits significantly decreased in patients undergoing lifestyle intervention (MSU volume P = 0.007; MSU score P = 0.001), and in patients treated with allopurinol (MSU volume and score P < 0.001) or febuxostat (MSU volume P < 0.001; MSU score P = 0.001). No significant decline in MSU deposits was noted in patients who discontinued treatment.

CONCLUSION

These data show that lifestyle intervention and xanthine oxidase inhibitors significantly decrease the MSU deposit burden. Hence, conventional gout therapy not only lowers serum UA levels, but also reduces pathologic MSU deposits.

Failure to reach uric acid target of <0.36 mmol/L in hyperuricaemia of gout is associated with elevated total and cardiovascular mortality

Objective

To determine the impact of achieving serum uric acid (sUA) of <0.36 mmol/L on overall and cardiovascular (CV) mortality in patients with gout.

Methods

Prospective cohort of patients with gout recruited from 1992 to 2017. Exposure was defined as the average sUA recorded during the first year of follow-up, dichotomised as ≤ or >0.36 mmol/L. Bivariate and multivariate Cox proportional hazards models were used to determine mortality risks, expressed HRs and 95% CIs.

Results

Of 1193 patients, 92% were men with a mean age of 60 years, 6.8 years' disease duration, an average of three to four flares in the previous year, a mean sUA of 9.1 mg/dL at baseline and a mean follow-up 48 months; and 158 died. Crude mortality rates were significantly higher for an sUA of ≥0.36 mmol/L, 80.9 per 1000 patient-years (95% CI 59.4 to 110.3), than for an sUA of <0.36 mmol/L, 25.7 per 1000 patient-years (95% CI 21.3 to 30.9). After adjustment for age, sex, CV risk factors, previous CV events, observation period and baseline sUA concentration, an sUA of ≥0.36 mmol/L was associated with elevated overall mortality (HR=2.33, 95% CI 1.60 to 3.41) and CV mortality (HR=2.05, 95% CI 1.21 to 3.45).

Conclusions

Failure to reach a target sUA level of 0.36 mmol/L in patients with hyperuricaemia of gout is an independent predictor of overall and CV-related mortality. Targeting sUA levels of <0.36 mmol/L should be a principal goal in these high-risk patients in order to reduce CV events and to extend patient survival.

Effects of Allopurinol Dose Escalation on Bone Erosion and Urate Volume in Gout: A Dual-Energy Computed Tomography Imaging Study Within a Randomized, Controlled Trial

OBJECTIVE

To examine whether allopurinol dose escalation to achieve serum urate (SU) target can influence bone erosion or monosodium urate (MSU) crystal deposition, as measured by dual-energy computed tomography (DECT) in patients with gout.

METHODS

We conducted an imaging study of a 2-year randomized clinical trial that compared immediate allopurinol dose escalation to SU target with conventional dosing for 1 year followed by dose escalation to target, in gout patients who were receiving allopurinol and who had an SU level of ≥0.36 mmoles/liter. DECT scans of feet and radiographs of hands and feet were obtained at baseline, year 1, and year 2 visits. DECT scans were scored for bone erosion and urate volume.

RESULTS

Paired imaging data were available for 87 patients (42 in the dose-escalation group and 45 in the control group). At year 2, the progression in the CT erosion score was higher in the control group than in the dose-escalation group (+7.8% versus +1.4%; P = 0.015). Changes in plain radiography erosion or narrowing scores did not differ between groups. Reductions in DECT urate volume were observed in both groups. At year 2, patients in the control group who had an SU level of <0.36 mmoles/liter and patients in the dose-escalation group had reduced DECT urate volume (-27.6 to -28.3%), whereas reduction in DECT urate volume was not observed in control group patients with an SU level of ≥0.36 mmoles/liter (+1.5%) (P = 0.023).

CONCLUSION

These findings provide evidence that long-term urate-lowering therapy using a treat-to-SU-target strategy can influence structural damage and reduce urate crystal deposition in gout.

Radiologic evidence of symmetric and polyarticular monosodium urate crystal deposition in gout - A cluster pattern analysis of dual-energy CT

OBJECTIVES

To determine the clustering patterns of monosodium urate (MSU) crystal deposition and bone erosions among patients with gout requiring urate-lowering therapy (ULT) using dual-energy CT (DECT).

METHODS

DECT scans of bilateral hands/wrists, feet/ankles, and knees were obtained on 153 patients with gout on allopurinol ≥300 mg daily for ≥3 months. Two radiologists assessed the images at pre-specified sites (15 in the hands/wrists, 12 in the feet/ankles, 4 in the knees). Clustering patterns of MSU crystal deposition and bone erosions were evaluated.

RESULTS

Among 153 patients with gout (mean duration, 15 years) on allopurinol (mean duration, 5 years), MSU crystal deposition (67%) affected multiple sites in the hands/wrists, feet/ankles, and knees more often than would be expected by chance (p<0.001 for all 3 regions). In the feet/ankles, bone erosions were also observed in a clustered manner (p<0.001). Presence of MSU crystal deposition at a particular joint was most strongly associated with symmetric involvement of the same joint of the opposite extremity in the hands/wrists, feet/ankles, and knees (adjusted odds ratio (OR) 26.1, 46.9, and 9.9, respectively). Similarly, presence of erosions in the feet/ankles was highly symmetric (adjusted OR 91.4). Erosions were 8-fold more likely to be present in sites with MSU crystal deposition compared to those without.

CONCLUSION

Among patients with longstanding gout on ULT, MSU crystal deposition and bone erosions affect multiple joints within the hands/wrists, feet/ankles, and knees in a highly symmetric manner. These radiologic data support the notion of MSU crystal deposition in gout as a symmetric polyarthropathy.

Concurrent validity of provisional remission criteria for gout: a dual-energy CT study

Background

Provisional gout remission criteria including five domains (serum urate, tophus, flares, pain due to gout, and patient global assessment) have been proposed. The aim of this study was to test the concurrent validity of the provisional gout remission criteria by comparing the criteria with dual-energy CT (DECT) findings.

Methods

Patients with gout on allopurinol ≥ 300 mg daily were prospectively recruited into a multicenter DECT study. Participants attended a standardized study visit which recorded gout flare frequency in the preceding 12 months, physical examination for tophus, serum urate, and patient questionnaires. DECT scans of both hands/wrists, feet/ankles/Achilles, and knees were analyzed by two DECT radiologists. The relationship between the DECT urate crystal volume and deposition with individual domains as well as the provisional remission criteria set was analyzed.

Results

The provisional remission criteria were fulfilled in 23 (15.1%) participants. DECT urate crystal deposition was observed less frequently in those fulfilling the provisional remission criteria (44%), compared with those not fulfilling the criteria (73.6%, odds ratio 0.28, P = 0.004). The median (range) DECT urate crystal volume was 0.00 (0.00–0.46) cm³ for those fulfilling the remission criteria, compared with 0.08 (0.00–19.53) cm³ for those not fulfilling the criteria (P = 0.002). In multivariate regression analysis, the serum urate and tophus domains were most strongly associated with DECT urate crystal deposition.

Conclusions

In people with gout established on allopurinol, a state of remission as defined by the provisional remission criteria is associated with less DECT urate crystal deposition. While this study provides support for the validity of the provisional gout remission criteria, it also demonstrates that some crystal deposition may be present in people achieving these criteria.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1941-8) contains supplementary material, which is available to authorized users.

2018 updated European League Against Rheumatism evidence-based recommendations for the diagnosis of gout

Although gout is the most common inflammatory arthritis, it is still frequently misdiagnosed. New data on imaging and clinical diagnosis have become available since the first EULAR recommendations for the diagnosis of gout in 2006. This prompted a systematic review and update of the 2006 recommendations. A systematic review of the literature concerning all aspects of gout diagnosis was performed. Recommendations were formulated using a Delphi consensus approach. Eight key recommendations were generated. A search for crystals in synovial fluid or tophus aspirates is recommended in every person with suspected gout, because demonstration of monosodium urate (MSU) crystals allows a definite diagnosis of gout. There was consensus that a number of suggestive clinical features support a clinical diagnosis of gout. These are monoarticular involvement of a foot or ankle joint (especially the first metatarsophalangeal joint); previous episodes of similar acute arthritis; rapid onset of severe pain and swelling; erythema; male gender and associated cardiovascular diseases and hyperuricaemia. When crystal identification is not possible, it is recommended that any atypical presentation should be investigated by imaging, in particular with ultrasound to seek features suggestive of MSU crystal deposition (double contour sign and tophi). There was consensus that a diagnosis of gout should not be based on the presence of hyperuricaemia alone. There was also a strong recommendation that all people with gout should be systematically assessed for presence of associated comorbidities and risk factors for cardiovascular disease, as well as for risk factors for chronic hyperuricaemia. Eight updated, evidence-based, expert consensus recommendations for the diagnosis of gout are proposed.

Recent developments in advanced imaging in gout

The plain radiographic features of gout are well known; however, the sensitivity of plain radiographs alone for the detection of signs of gout is poor in acute disease. Radiographic abnormalities do not manifest until late in the disease process, after significant joint and soft tissue damage has already occurred. The advent of dual-energy computed tomography (DECT) has enabled the non-invasive diagnosis and quantification of gout by accurately confirming the presence and extent of urate crystals in joints and soft tissues, without the need for painful and often unreliable soft tissue biopsy or joint aspiration. Specific ultrasound findings have been identified and may also be used to aid diagnosis. Both ultrasound and magnetic resonance imaging (MRI) may be used for the measurement of disease extent, monitoring of disease activity or treatment response, although MRI findings are nonspecific. In this article we summarize the imaging findings and diagnostic utility of plain radiographs, ultrasound, DECT, MRI and nuclear medicine studies in the assessment as well as the implications and utility these tools have for measuring disease burden and therapeutic response.

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.