Diagnostic accuracy of ultrasound in patients with gout: A meta-analysis

Advanced Imaging of Gout and Other Inflammatory Diseases Around the Knee

The knee is one of the most commonly affected joints in the course of inflammatory arthropathies, such as crystal-induced and autoimmune inflammatory arthritis. The latter group includes systemic connective tissue diseases and spondyloarthropathies. The different pathogenesis of these entities results in their varied radiologic images. Some lead quickly to joint destruction, others only after many years, and in the remaining, destruction will not be a distinguishing radiologic feature.Radiography, ultrasonography, and magnetic resonance imaging have traditionally been the primary modalities in the diagnosis of noninflammatory and inflammatory arthropathies. In the case of crystallopathies, dual-energy computed tomography has been introduced. Hybrid techniques also offer new diagnostic opportunities. In this article, we discuss the pathologic findings and imaging correlations for crystallopathies and inflammatory diseases of the knee, with an emphasis on recent advances in their imaging diagnosis.

Systematic literature review to inform the EULAR recommendations for the use of imaging in crystal-induced arthropathies in clinical practice

OBJECTIVE

To summarise current data regarding the use of imaging in crystal-induced arthropathies (CiAs) informing a European Alliance of Associations for Rheumatology task force.

METHODS

We performed four systematic searches in Embase, Medline and Central on imaging for diagnosis, monitoring, prediction of disease severity/treatment response, guiding procedures and patient education in gout, calcium pyrophosphate dihydrate deposition (CPPD) and basic calcium phosphate deposition (BCPD). Records were screened, manuscripts reviewed and data of the included studies extracted. The risk of bias was assessed by validated instruments.

RESULTS

For gout, 88 studies were included. Diagnostic studies reported good to excellent sensitivity and specificity of dual-energy CT (DECT) and ultrasound (US), high specificity and lower sensitivity for conventional radiographs (CR) and CT. Longitudinal studies demonstrated sensitivity to change with regard to crystal deposition by US and DECT and inflammation by US and structural progression by CR and CT. For CPPD, 50 studies were included. Diagnostic studies on CR and US showed high specificity and variable sensitivity. There was a single study on monitoring, while nine assessed the prediction in CPPD. For BCPD, 56 studies were included. There were two diagnostic studies, while monitoring by CR and US was assessed in 43 studies, showing a reduction in crystal deposition. A total of 12 studies with inconsistent results assessed the prediction of treatment response. The search on patient education retrieved two studies, suggesting a potential role of DECT.

CONCLUSION

This SLR confirmed a relevant and increasing role of imaging in the field of CiAs.

An Atypical Presentation of a Polyarticular Gout Flare: Case Report

A 54-year-old man with a history of hypertension, atrial fibrillation, chronic kidney disease, nonischemic cardiomyopathy, osteoarthritis, and gout presented to the emergency department (ED) with dysuria, painful scrotal swelling, severe bilateral flank pain, back pain, atraumatic right arm (elbow and distally) pain and swelling, and bilateral knee pain. His physical exam was notable for fever, tachycardia, bilateral costovertebral angle (CVA) tenderness, exquisite pain, erythema, and swelling of bilateral knees and the right arm (elbow and distally). He met Systemic Inflammatory Response Syndrome (SIRS) criteria, was placed on Ceftriaxone for presumed septic pyelonephritis, and was admitted to the medicine team. With initially unremarkable imaging studies, the differential diagnosis was broadened, and subsequent infectious workups yielded grossly normal results. At the end of hospital day one, the patient remained febrile and without symptomatic improvement. Rheumatology was consulted and empirically treated; the patient with a dose of Anakinra due to concerns about a polyarticular flare of crystalline arthropathy. Subsequent arthrocentesis confirmed a final diagnosis of a polyarticular gout flare. This case highlights the diagnostic challenges a polyarticular gout flare poses and the importance of early involvement of specialists for prompt recognition, treatment, and avoidance of unnecessary interventions.

Identification of tophi in ultrasound imaging based on transfer learning and clinical practice

Gout is a common metabolic disorder characterized by deposits of monosodium urate monohydrate crystals (tophi) in soft tissue, triggering intense and acute arthritis with intolerable pain as well as articular and periarticular inflammation. Tophi can also promote chronic inflammatory and erosive arthritis. 2015 ACR/EULAR Gout Classification criteria include clinical, laboratory, and imaging findings, where cases of gout are indicated by a threshold score of ≥ 8. Some imaging-related findings, such as a double contour sign in ultrasound, urate in dual-energy computed tomography, or radiographic gout-related erosion, generate a score of up to 4. Clearly, the diagnosis of gout is largely assisted by imaging findings; however, dual-energy computed tomography is expensive and exposes the patient to high levels of radiation. Although musculoskeletal ultrasound is non-invasive and inexpensive, the reliability of the results depends on expert experience. In the current study, we applied transfer learning to train a convolutional neural network for the identification of tophi in ultrasound images. The accuracy of predictions varied with the convolutional neural network model, as follows: InceptionV3 (0.871 ± 0.020), ResNet101 (0.913 ± 0.015), and VGG19 (0.918 ± 0.020). The sensitivity was as follows: InceptionV3 (0.507 ± 0.060), ResNet101 (0.680 ± 0.056), and VGG19 (0.747 ± 0.056). The precision was as follows: InceptionV3 (0.767 ± 0.091), ResNet101 (0.863 ± 0.098), and VGG19 (0.825 ± 0.062). Our results demonstrate that it is possible to retrain deep convolutional neural networks to identify the patterns of tophi in ultrasound images with a high degree of accuracy.

Single photon emission computed tomography/computed tomography imaging of gouty arthritis: A new voice

Gouty arthritis, often referred to simply as gout, is a disorder of purine metabolism characterized by the deposition of monosodium urate monohydrate (MSU) crystals in multiple systems and organs, especially in joints and their surrounding soft tissue. Gout is a treatable chronic disease, and the main strategy for effective management is to reverse the deposition of MSU crystals by uric acid reduction, and to prevent gout attacks, tophi deposition and complications, and thereby improve the quality of life. However, the frequent association of gout with other conditions such as hypertension, obesity, cardiovascular disease, diabetes, dyslipidemia, chronic kidney disease (CKD) and kidney stones can complicate the treatment of gout and lead to premature death. Here, we review the use of medical imaging techniques for studying gouty arthritis with special interest in the potential role of single photon emission computed tomography (SPECT)/computed tomography (CT) in the clinical management of gout and complications (e.g., chronic kidney disease and cardiovascular disease).

Agreement Among Multiple Observers on Crystal Identification by Synovial Fluid Microscopy

OBJECTIVE

Despite the fact that polarized microscopy remains the gold standard for diagnosing crystal arthritis, some uncertainties hamper full implementation in clinical practice. We undertook this study to analyze the agreement among multiple observers in crystal identification using compensated polarized microscopy, as well as to assess potential outcome modifiers.

METHODS

This was a cross-sectional, observational study with consecutive synovial fluid sampling. Samples were immediately analyzed when possible or kept refrigerated at 4°C. Five observers analyzed them separately, blinded to clinical data, using a compensated polarized optical microscope (400×), through 3 stages (ordinary, simple polarized, and compensated polarized light) to detect and identify crystals. They recorded the presence and type of crystal (no crystals, monosodium urate [MSU], and calcium pyrophosphate dihydrate [CPP]). Interrater agreement was measured by Cohen's kappa. Subanalyses were performed on visualization delay and cumulative expertise. Discrepancies between each stage of the microscopy and the final decision were also examined.

RESULTS

A total of 250 observations from 50 samples completed full assessment. Overall, κ = 0.74 (95% confidence interval [95% CI] 0.64-0.84), indicating good agreement. Agreement for crystal detection was κ = 0.71 (95% CI 0.59-0.82), for MSU was κ = 0.88 (95% CI 0.75-1.0), and for CPP was κ = 0.69 (95% CI 0.56-0.82). Most of the crystal identifications were already made by ordinary light. No differences between observations made before or after 24 hours (P = 0.859) or in expertise on crystal analysis (P = 0.989) were found. Observations performed under ordinary light matched the final diagnosis in 96.8% of cases (242 of 250).

CONCLUSION

Compensated polarized microscopy remained consistent in detecting and identifying crystals in synovial fluid, even when examined among multiple observers, confirming its high utility for clinical practice.

Presence of tophi and carotid plaque were risk factors of MACE in subclinical artherosclerosis patients with gout: a longitudinal cohort study

Background

Patients with gout carry an excess risk for cardiovascular disease (CVD), but the contribution of subclinical atherosclerosis to the CVD risk has never been reported. In this study, we aimed to explore the predictive factors for incident major adverse cardiovascular events (MACE) in gout patients without a previous history of CVD or cerebral vascular disease.

Methods

A single-center, long-term follow-up cohort analysis was performed to assess subclinical atherosclerosis at baseline since 2008. Patients with a previous history of CVD or cerebrovascular disease were excluded. The outcome of the study was the first MACE. The presence of subclinical atherosclerosis was assessed by carotid plaque (CP), and carotid intima-media thickness (CMIT) was determined by ultrasound. An ultrasound scan of bilateral feet and ankles was performed at baseline. The association between tophi, carotid atherosclerosis, and the risk of developing incident MACE was evaluated using Cox proportional hazards models with adjustment for the CVD risk scores.

Results

A total of 240 consecutive patients with primary gout were recruited. Their mean age was 44.0 years, with male predominance (238, 99.2%). During a median follow-up of 10.3 years, incident MACE was ascertained in 28 (11.7%) patients. In a Cox hazards model, controlling for the CV risk scores, the presence of at least two tophi (HR, 2.12-5.25, p < 0.05) and carotid plaque (HR, 3.72-4.01, p < 0.05) were identified as independent predictors of incident MACE in gout patients.

Conclusions

The presence of at least two tophi and carotid plaque on an ultrasound could independently predict MACE in addition to conventional cardiovascular risk factors in gout patients.

Mapping Knowledge Structure and Global Research Trends in Gout: A Bibliometric Analysis From 2001 to 2021

Background

The incidence and prevalence of gout have been steadily increasing globally, which has resulted in gout research attracting consistently increased attention. This study aimed to visualize the knowledge structure and research trends in gout research through bibliometrics to help understand the future development of basic and clinical research.

Methods

Articles and reviews on gout from 2001 to 2021 were extracted from the Web of Science Core Collection database. CiteSpace and VOSviewer software were used to visualize the knowledge network of countries, institutions, authors, references, and keywords in this field. SPSS and Microsoft Excel software were used for curve fitting and correlation analysis.

Results

A total of 3,259 articles and reviews were included. The number of publications about gout significantly increased yearly. Publications were mainly concentrated in North America, Europe, Oceania, and East Asia. The USA contributed most with 1,025 publications, followed by China and New Zealand. After adjusting for publications by population size and Gross Domestic Product (GDP), New Zealand ranked in the first place. GDP and international collaboration were significantly correlated with scientific productivity for gout research. University of Auckland and Professor Dalbeth Nicola were the most prolific institutions and influential authors, respectively. Rheumatology was the most productive journal for gout research. Gout research hotspots have shifted over time in the following order: clinical features, pathological mechanisms, complications, gouty arthritis, epidemiology, and dual-energy computed tomography to drug clinical trials, which can be observed from the keyword analysis and co-cited reference cluster analysis.

Conclusions

This study found that research on gout is flourishing. The development and experimentation of drugs for the prevention and treatment of gouty arthritis would be the focus of current research and developmental trends in future research.

Clinical diagnostic value of liquid chromatography-tandem mass spectrometry method for primary aldosteronism in patients with hypertension: A systematic review and meta-analysis

BACKGROUND

Primary aldosteronism (PA) is currently considered the most common cause of secondary and endocrine hypertension. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a new detection technique has been gradually applied in the diagnosis of PA. However, the diagnostic value of LC-MS/MS methods for PA has not been systematically clinically validated. The aim was to access the diagnostic accuracy, sensitivity, and specificity of LC-MS/MS methods as screening tools in PA.

MATERIALS AND METHODS

A literature search of PubMed, Embase, Medline, Web of Science, Scopus, Science Direct, and Chinese databases was carried out to June 2022 with no language restriction. Data on sensitivity and specificity and other evaluation indicators were extracted and pooled with STATA and Meta-disc software. Heterogeneity was evaluated and meta-regression and subgroup analysis was performed to elucidate sources of heterogeneity.

RESULTS

12 studies of the diagnostic test were suitable and included in the meta-analysis. Pooled sensitivity, specificity, and diagnostic odds ratio were 0.89 (95% CI: 0.83-0.93), 0.87 (95% CI: 0.82-0.91), and 55 (95% CI: 28-110), respectively. Subgroup analysis assessed the diagnostic power of LC-MS/MS based on the type of detection index. ARR and PAC based on LC-MS/MS methods have the higher diagnostic value compared with other indices, diagnostic odds ratios were 121.65 (95% CI: 36.28-407.98) and 49.85 (95% CI: 24.87-99.93). There was considerable heterogeneity among studies.

CONCLUSION

LC-MS/MS methods had higher accuracy and reliability in the diagnosis of primary aldosteronism. LC-MS/MS-based ARR and PAC can be further promoted and applied in the diagnosis of primary aldosteronism.

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.

Reliability of knee joint sonography in the evaluation of gouty arthritis

Objective: To determine the reliability of knee joint sonography in the evaluation of gouty arthritis. Methodology: A search of Google Scholar, PubMed, NCBI, MEDLINE, and Medscape databases, from 1988 up to 2020. The key search terms used were knee joint; knee joint ultrasound; gout; gouty arthritis, knee joint pain; sensitivity; specificity. The reviewer independently screened the titles and abstracts of the relevant articles and full-text downloads to determine whether the inclusion or exclusion criteria were met. Results: In total, 103 articles were identified through the database search. In addition, 11 articles were identified through other sources. Then, screening was performed, and 9 articles were removed due to duplication. Further screening was done for 105 articles, and 27 articles were excluded due to insufficient information. Seventy-eight full-text articles were assessed for eligibility. A total of 13 full-text articles were excluded due to research performed on animals, as the study had been designed as a review of only human studies. Sixty-three studies were included that had a qualitative synthesis. Conclusion: The knee is a weight-bearing joint and may be affected by a myriad of different pathological conditions, therefore a proper diagnosis is of prime importance for a proper management plan. Ultrasound is a non-invasive, radiation-free, and readily available modality that has high sensitivity and specificity in the evaluation of gouty arthritis.

Diagnostic value of different imaging features for patients with suspected gout: A network meta-analysis

OBJECTIVE

Microscopic identification of monosodium urate (MSU) crystals is the gold standard for gout diagnosis. However, joint aspiration is not always practical, and imaging is increasingly used in clinical practice. This study aimed to assess the diagnostic accuracy of imaging features for gout compared with microscopy, using network meta-analysis methodology.

METHODS

MEDLINE, EMBASE, PubMed and Cochrane databases were searched for studies reporting on the use of imaging modalities to diagnose gout in patients with an unclear diagnosis or suspected gout, which was later confirmed by microscopy. A combination of direct and indirect comparisons were performed by network meta-analysis to evaluate the combined odds ratios for sensitivity, specificity, and accuracy. To assist interpretation, the surface under the cumulative ranking curve (SUCRA) scores were calculated to provide a ranking of the imaging features.

RESULTS

Fifteen eligible studies were included. Compared to the gold standard microscopic identification of MSU crystals, dual energy computed tomography (DECT) MSU crystal deposition and ultrasound double contour had greater sensitivity than ultrasound tophus. DECT, ultrasound double contour sign and ultrasound tophus all had greater specificity than ultrasound aggregates. The SUCRA scores ranked DECT as highest for overall accuracy, followed by ultrasound double contour, aggregates, and tophus, while ultrasound snowstorm was ranked the lowest. However, there were no significant differences in the odds ratios for overall accuracy between these imaging features.

CONCLUSION

DECT and ultrasound are both useful modalities for the detection of imaging features of MSU crystal deposition, and have a similar overall diagnostic accuracy for gout diagnoses.

Quantitative assessment of crystal dissolution in gout during urate-lowering therapy with computer-aided MicroPure imaging: a cohort study

Background

To evaluate whether MicroPure imaging, an ultrasound (US) image-processing technique with computer-aided analysis, can quantitatively detect crystal dissolution during urate-lowering therapy (ULT) in gout.

Methods

This was a prospective study of gout patients requiring ULT. The first metatarsophalangeal joints were examined using US and MicroPure before and after 3 months of ULT. Elementary lesions of gout, including the double contour sign (DCS), aggregates, tophi, erosion, and other US features were recorded at baseline and 3 months. MicroPure imaging features were automatically calculated by a self-developed software. Patients were divided into goal-achieved and goal-not-achieved groups according to their urate levels at 3 months. The US and MicroPure imaging features of the two groups were analyzed at baseline and 3 months.

Results

A total of 55 consecutive patients were enrolled (25: goal-achieved group; 30: goal-not-achieved group). US findings demonstrated that the power Doppler signal grade decreased at 3 months, regardless of the group (both P<0.05). From baseline to 3 months, tophi size and the DCS reduced in the goal-achieved group (both P<0.05), while the US aggregate features showed no difference (P=0.250). However, on the MicroPure imaging, the number and density of aggregates at 3 months decreased in the goal-achieved group (both P<0.05). There were no significant changes at 3 months in any of the MicroPure imaging features in the goal-not-achieved group (all P>0.05).

Conclusions

In comparison with B-mode US, computer-aided MicroPure imaging can sensitively and quantitatively detect aggregate dissolution during effective ULT after only 3 months of treatment.

The role of dual energy computed tomography in the differentiation of acute gout flares and acute calcium pyrophosphate crystal arthritis

Objectives

To analyse the diagnostic impact of dual energy computed tomography (DECT) in acute gout flares and acute calcium pyrophosphate (CPP) crystal arthritis when compared to the gold standard of arthrocentesis with compensated polarised light microscopy. Microscopy results were also compared to musculoskeletal ultrasound (MUS), conventional radiographs, and the suspected clinical diagnosis (SCD).

Methods

Thirty-six patients with a suspected gout flare (n = 24) or acute CPP crystal arthritis (n = 11, n = 1 suffered from neither) who received a DECT and underwent arthrocentesis were included. Two independent readers assessed DECT images for signs of monosodium urate crystals or calcium pyrophosphate deposition.

Results

Sensitivity of DECT for gout was 63% (95% CI 0.41–0.81) with a specificity of 92% (0.41–0.81) while sensitivity and specificity for acute CPP arthritis were 55% (0.23–0.83) and 92% (0.74–0.99), respectively. MUS had the highest sensitivity of all imaging modalities with 92% (0.73–0.99) and a specificity of 83% (0.52–0.98) for gout, while sensitivity and specificity for acute CPP crystal arthritis were 91% (0.59–1.00) and 92% (0.74–0.99), respectively.

Conclusion

DECT is an adequate non-invasive diagnostic tool for acute gout flares but might have a lower sensitivity than described by previous studies. Both MUS and SCD had higher sensitivities than DECT for acute gout flares and acute CPP crystal arthritis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10067-021-05949-4.

Analysis of Risk Factors for Changes in the Renal Two-Dimensional Image in Gout Patients

OBJECTIVE

To explore the effects of different blood uric acid levels in gout patients on the two-dimensional image of the kidney and the risk factors for gout-related kidney damage for providing clinical evidence to enable early prevention and treatment of gout-related kidney damage.

METHODS

We obtained information of 227 patients with primary gout and estimated the association between two-dimensional kidney images and clinical indicators using binary logistic regression.

RESULTS

Our study showed that different uric acid levels, age, disease course, cystatin C (CysC) level, and γ-glutamyl transpeptidase level were correlated with echo of the renal medulla (P < 0.05). CysC level was correlated with the renal cortex thickness and kidney stones in different uric acid-level groups (P < 0.05). Disease course, aspartate transaminase (AST) level, creatinine (CREA) level, and tophi were risk factors for renal cortex thinning in gout patients (P = 0.045, 0.026, 0.004, 0.006, respectively). The disease course, platelet (PLT) count, and high-density lipoprotein (HDL-C) level were risk factors for kidney stone formation in gout patients (P = 0.037, 0.022, 0.023, respectively), while CysC level and C-reactive protein (CRP) level were risk factors for increased renal medulla echo in these patients (P = 0.022, 0.028, respectively).

CONCLUSION

Our study revealed disease course, AST level, CREA level, tophi, PLT count, HDL-C level, CysC level and CRP level may be important predictors of renal image changes.

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.

Differential Diagnosis of Acute and Chronic Gouty Arthritis by Multijoint Ultrasound

To investigate whether multi-joint ultrasound (US) findings in patients with gouty arthritis could be used to distinguish between acute and chronic stages, we performed a retrospective study with 129 enrolled patients from the Rheumatology Department of the First Affiliated Hospital of Chengdu Medical College from September 1, 2018 to June 12, 2019. Patients with acute or non-acute gout were categorized using clinical data, and US imaging findings of the knees, ankles and first metatarsophalangeal joints were analyzed and compared between groups. Notably, we found that the most prevalent sign detected by US was the hyperechoic spot in the synovium, followed by arthrosynovitis, aggregates, double contour signs and tophi; meanwhile, bone erosions were the least common. Additionally, synovitis was more frequently detected in the acute joints of gouty arthritis (49%) compared with the non-acute joints (35%), whereas grade 1 or 2 blood flow classifications (97%), tophi and bone lesions were more often seen in the latter. Overall, our data suggest that multi-joint US scanning might be used to evaluate disease severity and discriminate between stages of gouty arthritis.

X-ray dark-field radiography for in situ gout diagnosis by means of an ex vivo animal study

Gout is the most common form of inflammatory arthritis, caused by the deposition of monosodium urate (MSU) crystals in peripheral joints and tissue. Detection of MSU crystals is essential for definitive diagnosis, however the gold standard is an invasive process which is rarely utilized. In fact, most patients are diagnosed or even misdiagnosed based on manifested clinical signs, as indicated by the unchanged premature mortality among gout patients over the past decade, although effective treatment is now available. An alternative, non-invasive approach for the detection of MSU crystals is X-ray dark-field radiography. In our work, we demonstrate that dark-field X-ray radiography can detect naturally developed gout in animals with high diagnostic sensitivity and specificity based on the in situ measurement of MSU crystals. With the results of this study as a potential basis for further research, we believe that X-ray dark-field radiography has the potential to substantially improve gout diagnostics.

Sonographic estimation of monosodium urate burden predicts the fulfillment of the 2016 remission criteria for gout: a 12-month study

Objective

To investigate whether baseline monosodium urate (MSU) burden estimated by ultrasound (US) predicts the achievement of the 2016 remission criteria for gout after 12 months.

Methods

In this 12-month prospective, observational and single-center study, patients with gout fulfilling all the domains of the 2016 preliminary remission criteria for gout at baseline and on urate-lowering therapy (ULT) for at least the preceding 6 months were consecutively enrolled.

The US findings indicative of MSU deposits [aggregates, double contour (DC) sign, and/or tophi] were identified according to the Outcome Measure in Rheumatology US Working Group definitions.

The US MSU burden was estimated by evaluating elbows, wrists, 2nd metacarpophalangeal joints, knees, ankles, and 1st metatarsophalangeal joints.

Results

Remission criteria were fulfilled in 21 (42.0%) out of 50 patients at 12 months. The baseline US MSU burden was significantly lower in patients who achieved remission than in those who did not fulfill the remission criteria at 12 months (1.9±1.8 vs 5.1±3.1, p<0.01).

US scores and ongoing flare prophylaxis were the only significant predictors of remission with an odds ratio of 10.83 [(95%CI=1.14–102.59), p=0.04] for the absence of MSU deposits, 5.53 [(95%CI=1.34–22.76), p<0.01] for the absence of aggregates, 7.33 [(95%CI=1.71–31.44), p<0.01] for the absence of DC sign, 3.88 [(95%CI=1.08–13.92), p=0.04] for the absence of tophi, and 0.23 [(95%CI=0.07–0.75), p=0.02] for ongoing flare prophylaxis.

Conclusion

In gout, baseline US estimation of MSU burden is an independent predictor of the achievement of the remission criteria at 12 months.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02568-x.

Ultrasound Evaluation of Three Outcome Domains in the Follow-up of Urate-Lowering Therapy in Gout: An Observational Study

This prospective study was aimed at observing the changes in three ultrasound (US) outcome domains (urate deposition, joint inflammation and bone erosion) in gout patients within the 1 y on urate-lowering therapy. The elementary lesions, including tophus, double-contour (DC) sign, aggregates, synovitis and bone erosion of the bilateral knee, ankle and first metatarsophalangeal joints, were evaluated repeatedly by US before and after 3, 6 and 12 mo of treatment, and the effective rates of clearance of tophus, DC sign and aggregates in different time groups were compared. A Global OMERACT-EULAR Synovitis Score (GLOESS) was calculated for these three paired joints to observe the inflammation. Bone erosion was also scored. The correlation between serum uric acid levels and tophus size changes was analyzed. Our results indicated that the decrease in serum uric acid levels was not completely parallel to the decrease in tophus size. For tophus, there was no significant difference in the clearance rate between different time groups (χ² = 1.76, p = 0.392), while for DC sign and aggregates, there were significant differences (χ² = 21.48, p < 0.001, χ² = 7.75, p = 0.018). Meanwhile, GLOESS was significantly lower after 6 mo of therapy (χ² = 32.316, p < 0.001). Additionally, bone erosion had not improved after 1 y of treatment (Z = -1.633, p = 0.102). Thus, US is crucial for assessing response to urate-lowering therapy in gout.

Images in Primary Care Medicine: Point-of-Care Ultrasound in Gout

Gout is the most common crystal arthropathy and is frequently diagnosed and managed by primary care physicians. Point-of-care ultrasound (POCUS) is a valuable tool to aid in the diagnosis of gout via the identification of the double contour sign, aggregates of crystals, tophi, and erosions. In addition, POCUS can aid in the management of gout by recognizing early signs of gout, monitoring the effectiveness of urate-lowering therapy, and guiding aspiration and corticosteroid injection.

Gout

Gout is a common and treatable disease caused by the deposition of monosodium urate crystals in articular and non-articular structures. Increased concentration of serum urate (hyperuricaemia) is the most important risk factor for the development of gout. Serum urate is regulated by urate transporters in the kidney and gut, particularly GLUT9 (SLC2A9), URAT1 (SLC22A12), and ABCG2. Activation of the NLRP3 inflammasome by monosodium urate crystals with release of IL-1β plays a major role in the initiation of the gout flare; aggregated neutrophil extracellular traps are important in the resolution phase. Although presenting as an intermittent flaring condition, gout is a chronic disease. Long-term urate lowering therapy (eg, allopurinol) leads to the dissolution of monosodium urate crystals, ultimately resulting in the prevention of gout flares and tophi and in improved quality of life. Strategies such as nurse-led care are effective in delivering high-quality gout care and lead to major improvements in patient outcomes.

An Unusual Presentation of Gout Involving the Ankle Ligaments

Gout is the most common inflammatory arthritis due to deposition of monosodium urate (MSU) crystals in joints and connective tissues. In contrast to joint disease, the majority of extra-articular involvement remains asymptomatic in patients with gout. Achilles tendon is the most common site of involvement and the inflammation elicited by MSU crystals can be falsely attributed to injury or overuse. In addition, tendon or ligament damage secondary to MSU crystal deposition can lead to ligament tear or tendon rupture.

However, the diagnosis of gout in patients with extra-articular involvement is often delayed or even missed because tissue sampling is not feasible in routine clinical practice. Advanced imaging techniques using ultrasound and dual-energy computer tomography (DECT) can detect MSU crystal deposition in a non-invasive manner and confirm the diagnosis of gout in patients with extra-articular involvement.

The following case demonstrates an atypical presentation of gout causing multiple ligament tears in the ankle and highlights the role of DECT in the diagnosis of gout with extra-articular involvement.

Ultrasonography and dual-energy computed tomography: impact for the detection of gouty deposits

Ultrasonography (US) and dual-energy computed tomography (DECT) are useful and sensitive diagnostic tools to identify monosodium urate deposits in joints and soft tissues. The purpose of this review is to overview the imaging findings obtained by US and DECT in patients with gout, to understand the strengths and weaknesses of each imaging modality, and to evaluate the added value of using both modalities in combination.

Ultrasound shows rapid reduction of crystal depositions during a treat-to-target approach in gout patients: 12-month results from the NOR-Gout study

OBJECTIVES

As ultrasound is sensitive for detecting crystal depositions in patients with gout, our objectives were to explore the main locations for depositions and the extent of dissolution of depositions during a treat-to-target approach with urate lowering treatment (ULT) in patients with gout.

METHODS

Patients with a recent flare of gout were consecutively included in this single-centre study and managed by a treat-to-target approach with ULT. All patients were assessed at baseline, 3, 6 and 12 months including bilateral ultrasound examinations of joints/tendons/entheses of hands, elbows, knees, ankles and feet. A new semiquantitative scoring system of 0-3 of elementary lesions (double contour (DC), tophi and aggregates) was applied to quantify the amount of depositions during the follow-up.

RESULTS

209 of the patients were evaluated with ultrasound at baseline (mean (SD) age 56.4 (13.8) years and disease duration 7.9 (7.7) years, 95.2% men). The serum urate levels decreased from baseline to 12 months (mean (SD) 500 (77) to 312 (49) µmol/L) (p<0.001)). The first metatarsophalangeal joint was the most frequent location for all the elementary lesions and erosions were associated with higher levels of crystal depositions. From baseline to 12 months, mean sum scores decreased for DC (4.3 to 1.3), tophi (6.5 to 3.8) and aggregates (9.3 to 6.7) (p<0.001 for all), with DC being most sensitive to change.

CONCLUSIONS

The ultrasound scoring system for crystal depositions was sensitive to change and showed that a treat-to-target approach with ULT resulted in significant reductions of all the depositions, most extensively for DC.

Scruples over Speckles

The “snowstorm” sign refers to the ultrasound appearance of motile hyperechoic specks within synovial fluid and has been reported to have a high specificity for gout. We describe three additional etiologies commonly encountered in the rheumatology clinic that can produce a snowstorm: calcium pyrophosphate deposition disease, fibrin collections/rice bodies, and gas bubbles in viscous synovial fluid.

Case with long-standing gout showing various ultrasonographic features caused by monosodium urate monohydrate crystal deposition

Gout, which is characterized by the deposition of monosodium urate monohydrate (MSU) in the synovial fluid and other tissues, is the most common form of inflammatory arthritis. Unlike the easily recognized acute and monoarticular gouty arthritis, advanced gout induces multiple finger joint disorders and may sometimes mimic rheumatoid arthritis (RA) or vice versa. The gold standard for gout diagnosis is the identification of MSU crystals via aspiration in the symptomatic joints or nodules; however, its feasibility and specificity may be inadequate. Recently, there have been important advances in imaging techniques, assisting in the non-invasive diagnosis of gout. Ultrasonography (US) has been known to have the ability to detect deposition of MSU crystals in patients with gout. Herein, we report an evocative case of long-standing gout with precisely detected specific US features indicating MSU crystal deposition and inflammation in multiple joints. Comprehensive US assessment included the bone, hyaline cartilage, soft tissue, subcutaneous nodules and tendon; we also discriminated gouty arthritis from RA.

Risk factors for the formation of double-contour sign and tophi in gout

BACKGROUND

This study aimed to confirm the diagnostic accuracy of ultrasound (US) on gout and explore the potential risk factors for double-contour sign and tophi formation in gout patients.

METHODS

The US analyses were performed on all knee, ankle, and first metatarsophalangeal (MTP 1) joints to reveal the type and location of lesions. While a questionnaire and blood biochemical index were used to explore the potential risk factors for double-contour sign and tophi in gout, the SPSS17.0 software was used for statistical analysis in the present study.

RESULTS

Totally, 117 gout patients with 702 joints (38 lesions in knee joint, 93 lesions in ankle joint, and 112 lesions in MTP 1 joint) were enrolled in current analyses. Double-contour sign and joint effusion were the two most outstanding lesion manifestations in knee joints and ankle joints. Tophi and double-contour sign were the two most outstanding lesion manifestations in TMP 1 joints. Moreover, factors including uric acid (UA) level and the highest blood UA were potential risk factors of the double-contour sign, while age and history of US were potential risk factors for tophi.

CONCLUSION

US was effective on the joints of gout patients. There was US sensitivity for tophi and double-contour sign in MTP 1 joints. The double-contour sign was a potential specific manifestation in knee joints and ankle joints. Furthermore, UA and highest blood UA level were potential risk factors for double-contour sign, while age and US history were potential risk factors for tophi.

Reliability of OMERACT ultrasound elementary lesions in gout: results from a multicenter exercise

The aim of this study was to evaluate the reliability of the outcome measures in rheumatology (OMERACT) definitions for ultrasound (US) elementary lesions in gout through an image reading exercise. Images from patients with gout (static images and videos) were collected. As an initial step, we carried out a image reading exercise within the experts of the Pan-American League of Associations for Rheumatology (PANLAR) US Study Group (n = 16). The following step consisted in a web-based exercise with the participation of larger number of sonographers (n = 63) from different centers. Images were rated evaluating the presence/absence of any US elementary lesion. Inter- and intra-reader reliabilities were analyzed using kappa coefficients. Participants were stratified according to their level of experience. In the first exercise, inter-reader kappa values were 0.45 for aggregates, 0.57 for tophus, 0.69 for erosions, and 0.90 for double contour (DC). Intra-reader kappa values were 0.86, 0.76, 0.80, and 0.90, respectively. The web-based exercise showed inter-reader kappa values for aggregates, tophus, erosions, and DC of 0.42, 0.49, 0.69, and 0.79, respectively. The intra-reader kappa values were 0.62, 0.69, 0.77, and 0.85, respectively. Reliability was not influenced by the sonographer's level of experience. The reliability of the new OMERACT US definitions for elementary lesions in gout ranged from moderate to excellent, depending on the type of lesion.

Current status of ultrasound and dual-energy computed tomography in the evaluation of gout

Gout is the most common inflammatory arthritis and is increasing in relevance due to its rising prevalence and incidence. Dual-energy CT (DECT) and ultrasound (US) are the most frequently used imaging modalities for the diagnosis of gout and for the follow-up of patients receiving therapy. Although DECT has the highest diagnostic accuracy for gout and shows consistently excellent reader agreement in the assessment of urate deposition change after therapy, US also performs well and remains just as important an imaging tool in these realms due to its practical advantages in cost, availability, and safety. This article reports the current status of these two modalities in regard to diagnosis and therapy follow-up.