A prospective evaluation of ultrasound as a diagnostic tool in acute microcrystalline arthritis

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.

Which are the most frequently involved peripheral joints in calcium pyrophosphate crystal deposition at imaging? A systematic literature review and meta-analysis by the OMERACT ultrasound – CPPD subgroup

Objectives

To identify the prevalence of calcium pyrophosphate crystal deposition (CPPD) using ultrasound and conventional radiology at peripheral joints in patients with suspected or definite CPPD.

Methods

A systematic literature search was performed in PubMed and Embase using pre-defined search strategies from inception to April 2021 to identify studies that evaluated conventional radiology and ultrasound in detecting CPPD at peripheral joints, including definite or suspected CPPD [Research question 1 (RQ1) and Research Question 2 (RQ2), respectively]. For the meta-analysis, the first, second, and third sub-analysis included studies with the knee, and knee or wrist as the index joint for CPPD (without restrictions on the reference standard) and synovial fluid analysis or histology as a reference standard (without restrictions on the index joint), respectively.

Results

One-thousand eight hundred and twenty-seven manuscripts were identified, of which 94 articles were finally included. Twenty-two and seventy-two papers were included in RQ1 and RQ2, respectively. The knee had the highest prevalence for RQ1 and RQ2 by both conventional radiology and ultrasound, followed by the wrist with the highest prevalence for RQ1. The hand had the lowest CPPD prevalence. The third sub-analysis showed a higher CPPD prevalence on ultrasound than conventional radiology at the knee (only data available).

Conclusion

Among all peripheral joints, the knees and wrists could be regarded as the target joints for CPPD detection by imaging. Furthermore, ultrasound seems to detect a higher number of calcium pyrophosphate deposits than conventional radiology, even when using a more restrictive reference standard.

Diagnostic Performance of Dual-energy CT Versus Ultrasonography in Gout: A Meta-analysis

OBJECTIVE

Dual-energy computed tomography (DECT), along with ultrasound (US), has been increasingly utilized for the diagnosis of gout because of its noninvasive advantages. However, the superiority of DECT over US remains controversial. This meta-analysis was performed to investigate whether DECT is superior to US in the diagnosis of gout.

METHODS

A comprehensive search of PubMed, EMBASE, Cochrane, and Web of Science databases was conducted for potentially eligible articles. Studies that evaluated the utility of DECT or US for gout diagnosis were qualified. Two distinctive ultrasonographic features of gout, namely, the double contour sign and the presence of tophus, were also assessed. The methodological quality of the included studies was evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 criteria. Besides, the subgroup analyses of early disease duration (≤ 2 years) was also performed.

RESULTS

Twenty-eight studies were included in the meta-analysis. The pooled sensitivity and specificity of DECT were 0.89 (0.80-0.94) and 0.91 (0.88-0.94), respectively. The pooled sensitivity and specificity of US were 0.70 (0.58-0.79) and 0.95 (0.87-0.98), respectively, for double contour sign; 0.57 (0.38-0.74) and 0.99 (0.88-1.00), respectively, for tophus; and 0.84 (0.73-0.91) and 0.84 (0.78-0.89), respectively, for overall consideration of US signs. At the early disease duration (≤ 2 years), the pooled sensitivity and specificity were 0.75 (0.60-0.86) and 0.85 (0.75-0.91), respectively, for DECT; 0.93 (0.72-0.99) and 0.80 (0.71-0.86), respectively, for overall consideration of US signs.

CONCLUSION

DECT and US showed promising accuracy for gout diagnosis. DECT has higher sensitivity, specificity, and AUC than overall consideration of US signs and thus has a better diagnostic ability in diagnosing gout. Moreover, the diagnostic sensitivity of DECT is lower than that of overall consideration of US signs at less than 2 years' disease duration.

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.

Unravelling the mysteries of gout by multimodality imaging

Gout is a common inflammatory arthritis that manifests as an aggregate of variably symptomatic monosodium urate crystals (MSU) in the joints and surrounding tissues in addition to multisystem involvement such as genitourinary and cardiovascular systems. In recent decades, there has been a documented increase in the prevalence and incidence of gout. Risk factors for gout include obesity, dietary influences, hypertension, renal impairment, and diuretic use. A prompt diagnosis followed by uric acid lowering treatment prior to the onset of bone destruction is the goal in any suspected case of gout. Advanced imaging modalities, such as dual energy computed tomography (DECT) and ultrasonography (US), employed for the diagnosis of gout are each accompanied by advantages and disadvantages. Conventional radiography (CR), although useful in visualizing joint erosions and mineralization, is limited in its ability to diagnose gout flare. Although synovial fluid aspiration remains the gold standard for MSU crystal visualization, less-invasive imaging modalities are preferred to avoid potential complications. DECT and US in particular are useful in the diagnosis of gout. In this review, we will discuss the current state and role of imaging in the detection of gout.

The diagnostic value of conventional radiography and musculoskeletal ultrasonography in calcium pyrophosphate deposition disease: a systematic literature review and meta-analysis

OBJECTIVE

To examine and compare the accuracy of conventional radiography (CR) and musculoskeletal ultrasonography (US) in the diagnosis of calcium pyrophosphate (CPP) crystals deposition disease (CPPD).

DESIGN

A systematic search of electronic databases (PubMed, Embase, and Cochrane), conference abstracts and reference lists was undertaken. Studies which evaluated the accuracy of CR and/or US in the diagnosis of CPPD, using synovial fluid analysis (SFA), histology or classification criteria as reference tests were included. Subgroup analyses by anatomic site and by reference test were performed.

RESULTS

Twenty-six studies were included. Using SFA/histology as reference test, CR and US showed an excellent (CR AUC = 0.889, 95%CI = 0.811-0.967) and an outstanding (US AUC = 0.954, 95%CI = 0.907-1.0) diagnostic accuracy (p < 0.01), respectively. Furthermore, US showed a higher sensitivity (0.85, 95%CI = 0.79-0.90 vs 0.47, 95%CI = 0.40-0.55) and only a little lower specificity (0.87, 95%CI = 0.83-0.91 vs 0.95, 95%CI = 0.92-0.97) than CR. A considerable heterogeneity between the studies was found, with adopted reference test being the main source of heterogeneity. In fact, subgroup analysis showed a significant change in the diagnostic accuracy of CR, but not of US, using Ryan and McCarty criteria or SFA/histology as reference test (CR: AUC = 0.956, 95%CI = 0.925-1.0 vs AUC = 0.889, 95%CI = 0.828-0.950, respectively, p < 0.01) (US: AUC = 0.922, 95%CI = 0.842-1.0 vs AUC = 0.957, 95%CI = 0.865-1.0, respectively, p = 0.08) CONCLUSIONS: Although US is more sensitive and a little less specific than CR for identifying CPP crystals, both these two techniques showed a great diagnostic accuracy and should be regarded as complementary to each other in the diagnostic work-up of patients with CPPD.

Performance of Ultrasound in the Clinical Evaluation of Gout and Hyperuricemia

Objective

To evaluate monosodium urate (MSU) crystal deposition and related lesions in the joints of patients with gout and hyperuricemia (HUA) using ultrasound. To explore the association between ultrasound findings and clinical features in gout and HUA.

Methods

A total of 202 patients with gout and 43 asymptomatic patients with HUA were included. The clinical data and ultrasonic assessment results were collected and statistically analyzed.

Results

Deposition of MSU crystals was found in 25.58% (11/43) of patients with asymptomatic HUA and 76.24% (154/202) of patients with gout. Of the 1,082 joints from patients with gout examined, 33.09% (358/1082) displayed MSU crystal deposition. In the joints with MSU crystal deposition, 77.37% (277/358) had a history of attacks. Among the joints of gouty arthritis, double contour sign (DCS), hyperechoic aggregate (HAG), and tophi were found in 32.65% (159/487), 7.80% (38/487), and 24.64% (120/487) of the joints, respectively. DCS and tophi, but not HAG, increasingly appeared with the extension of gout duration. In patients with more than 15 years of gout history, DCS, Tophi, and HAG were found in 48.18%, 40.00%, and 6.36% of US assessed joints, respectively. In patients with gout, synovial lesion and bone erosion were found in 17.74% (192/1082) and 7.58% (82/1082) of joints, respectively. The synovial lesion was related to HAG, while bone erosion was related to tophi and DCS. Nephrolithiasis was detected in 20.30% (41/202) of patients with gout and 4.65% (2/43) of HUA patients, indicating that nephrolithiasis occurred in more patients with gout than in patients with HUA.

Conclusion

HAG is an early performance of MSU crystal deposition in joints of gout and HUA. Both DCS and tophi are risk factors for bone erosion. Early urate-lowering therapy (ULT) should be considered in patients with gout, DCS, or tophi.

A critical review of the available evidence on the diagnosis and clinical features of CPPD: do we really need imaging?

Imaging has been playing an important role in the pathogenetic and clinical characterisation of many rheumatic diseases, especially in the most recent years with the advent of many new, highly technological and promising techniques. Calcium pyrophosphate deposition disease (CPPD) benefited also from these new techniques, most of which can readily identify calcium crystals. Nowadays, imaging is used mainly to identify crystals in joints but given the complexity of CPPD, imaging should be used with an "holistic" approach in order to gain insights in the pathogenesis, spectrum of clinical manifestations and natural history of the disease. Furthermore, overlap or association of CPPD with other prevalent diseases of the elderly makes the differential diagnosis challenging. In this review, we provide a critical review of the current knowledge on the use of imaging both for the identification of crystals and for its application in clinical practice as an aid for determining the impact of the disease on patients.Key Points• CPPD is a complex disease with a wide spectrum of clinical manifestations and understanding of pathogenetic mechanisms and clinical phenotypes is essential for correct characterisation• Imaging has made important advances regarding identification of CPPD in recent years, and new, more sophisticated techniques are under investigation• Imaging has the potential to improve our knowledge on pathogenesis and clinical phenotypes of CPPD• Imaging techniques have to be tested thoroughly for reliability, discrimination and sensitivity to change before they can be implemented in clinical trials.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Differential Diagnosis of Inflammatory Arthropathies by Musculoskeletal Ultrasonography: A Systematic Literature Review

Background: Differential diagnosis in early arthritis is challenging, especially early after symptom onset. Several studies applied musculoskeletal ultrasound in this setting, however, its role in helping diagnosis has yet to be clearly defined. The purpose of this work is to systematically assess the diagnostic applications of ultrasonography in early arthritis in order to summarize the available evidence and highlight possible gaps in knowledge. Methods: In December 2017, existing systematic literature reviews (SLR) on rheumatoid arthritis (RA), osteoarthritis (OA), psoriatic arthritis (PsA), polymyalgia rheumatica (PMR), calcium pyrophosphate deposition disease (CPPD), and gout were retrieved. Studies on ultrasound to diagnose the target conditions and detecting elementary lesions (such as synovitis, tenosynovitis, enthesitis, bone erosions, osteophytes) were extracted from the SLRs. The searches of the previous reviews were updated and data from new studies fulfilling the inclusion criteria extracted. Groups of reviewers worked separately for each disease, when possible diagnostic accuracy (sensitivities, specificities) was calculated from primary studies. When available, the reliability of ultrasound to detect elementary lesions was extracted. Results: For all the examined disease, recent SLRs were available. The new searches identified 27 eligible articles, with 87 articles included from the previous SLRs. The diagnostic performance of ultrasound in identifying diseases was addressed by 75 studies; in most of them, a single elementary lesion was used to define diagnosis, except for PMR. Only studies on RA included consecutive patients with new onset of arthritis, while studies on gout and CPPD often focused on subjects with mono-arthritis. Most of the remaining studies enrolled patients with a defined diagnosis. Synovitis was the most frequently detected lesion; clinical diagnosis was the most common reference standard. The diagnostic performance of ultrasound across different conditions was extremely variable. Ultrasound to identify elementary lesions was assessed in 38 studies in OA, gout and CPPD. Its performance in OA was very variable, with better results in CPPD and gout. The reliability of ultrasound was moderate to good for most lesions. Conclusions: Although a consistent amount of literature investigated the diagnostic application of ultrasound, in only a minority of cases its additional value over clinical diagnosis was tested. This SLR underlines the need for studies with a pragmatic design to identify the placement of ultrasound in the diagnostic pathway of new-onset arthritis.

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.

Ultrasound evaluation in follow-up of urate-lowering therapy in gout: the USEFUL study

OBJECTIVES

We aimed to determine the ability of ultrasonography (US) to show disappearance of urate deposits in gouty patients requiring urate-lowering therapy (ULT).

METHODS

We performed a 6-month multicentre prospective study including patients with: proven gout; presence of US features of gout (tophus and/or double contour sign) at the knee and/or first metatarsophalangeal joints; and no current ULT. US evaluations were performed at baseline and at months 3 and 6 (M3, M6) after starting ULT. Outcomes were: the change in US features of gout at M6 according to final (M6) serum urate (SU) level (high, > 360 μmol/l, i.e. > 6 mg/dl; low, 300-360 μmol/l, i.e. 5-6 mg/dl; very low, < 300 μmol/l, i.e. < 5 mg/dl); and correlation between changed US features and final SU level.

RESULTS

We included 79 gouty patients (mean ± s.d., age 61.8 (14) years, 91% males, disease duration 6.3 (6.1) years). Baseline SU level was 530 ± 97 µmol/l (i.e. 8.9 mg/dl ± 1.6mg/dl). At least one US tophus and double contour sign was observed in 74 (94%) and 68 (86%) patients, respectively. Among the 67 completers at M6, 18 and 39 achieved a very low and low SU level, respectively. We found a significant decrease in US features of gout among patients with the lowest SU level (P < 0.001). Final M6 SU level was positively correlated with decreased size of tophus (r = 0.54 [95% CI: 0.34, 0.70], P < 0.0001), and inversely correlated with proportion of double contour sign disappearance (r=-0.59 [-0.74, -0.40]).

CONCLUSION

US can show decreased urate deposition after ULT, which is correlated with decreased SU level. The responsiveness of US in gout is demonstrated and can be useful for gout follow-up and adherence to ULT.

Gout: state of the art after a decade of developments

This review article summarizes the relevant English literature on gout from 2010 through April 2017. It emphasizes that the current epidemiology of gout indicates a rising prevalence worldwide, not only in Western countries but also in Southeast Asia, in close relationship with the obesity and metabolic syndrome epidemics. New pathogenic mechanisms of chronic hyperuricaemia focus on the gut (microbiota, ABCG2 expression) after the kidney. Cardiovascular and renal comorbidities are the key points to consider in terms of management. New imaging tools are available, including US with key features and dual-energy CT rendering it able to reveal deposits of urate crystals. These deposits are now included in new diagnostic and classification criteria. Overall, half of the patients with gout are readily treated with allopurinol, the recommended xanthine oxidase inhibitor (XOI), with prophylaxis for flares with low-dose daily colchicine. The main management issues are related to patient adherence, because gout patients have the lowest rate of medication possession ratio at 1 year, but they also include clinical inertia by physicians, meaning XOI dosage is not titrated according to regular serum uric acid level measurements for targeting serum uric acid levels for uncomplicated (6.0 mg/dl) and complicated gout, or the British Society for Rheumatology recommended target (5.0 mg/dl). Difficult-to-treat gout encompasses polyarticular flares, and mostly patients with comorbidities, renal or heart failure, leading to contraindications or side effects of standard-of-care drugs (colchicine, NSAIDs, oral steroids) for flares; and tophaceous and/or destructive arthropathies, leading to switching between XOIs (febuxostat) or to combining XOI and uricosurics.

Prevalence and discrimination of OMERACT-defined elementary ultrasound lesions of gout in people with asymptomatic hyperuricaemia: A systematic review and meta-analysis

OBJECTIVES

Ultrasound lesions of gout have been described in people with asymptomatic hyperuricemia. However, the anatomical sites and ultrasound lesions most frequently involved in asymptomatic hyperuricemia have not yet been established. This systematic review and meta-analysis aimed to determine the prevalence of the Outcome Measures in Rheumatology (OMERACT) elementary ultrasound lesions of gout (double contour, aggregates, tophus, erosion) at various sites in people with asymptomatic hyperuricemia and to determine which sites and lesions discriminate from people with normouricemia.

METHODS

A systematic search of electronic databases, conference abstracts and reference lists was undertaken. Studies were included if they used ultrasound to image people with asymptomatic hyperuricemia and reported ≥1 OMERACT-defined lesion of gout. Meta-analyses were undertaken for the pooled prevalence of site-specific lesions in people with asymptomatic hyperuricemia, and the pooled odds ratios of these lesions compared to people with normouricemia.

RESULTS

Twenty studies were included. The most common site scanned was the first metatarsophalangeal joint (1MTP) (n = 17 studies) and the most common lesion reported, the double contour (n = 18). Meta-analyses of pooled prevalence showed 1MTP double contour was the most frequent finding in people with asymptomatic hyperuricemia (0.31, 95% confidence interval (CI) 0.20-0.42), followed by femoral condyle double contour (0.16, 95%CI 0.08-0.24) and 1MTP tophus (0.16, 95%CI 0.03-0.29). The highest pooled odds ratios for asymptomatic hyperuricemia vs. normouricemia were 6.98 (95%CI 3.14-15.57) for 1MTP double contour, 13.67 (95%CI 5.42-34.49) for femoral condyle double contour and 6.10 (95%CI 1.55-24.04) for 1MTP tophus.

CONCLUSION

In people with asymptomatic hyperuricemia, scanning of the 1MTP and femoral condyle for double contour, plus the 1MTP for tophus, has the highest prevalence and discrimination compared to those with normouricemia.

Subclinical crystal arthropathy: a silent contributor to inflammation and functional disability in knees with osteoarthritis-an ultrasound study

PURPOSE

This study aimed at investigating the prevalence of crystal deposits with knee osteoarthritis (OA) by ultrasonography and measure the inflammatory burden associated with crystal deposits in OA using WOMAC score.

METHODS

Adult patients with primary knee OA diagnosed according to the American College of Rheumatology criteria were included. Participants were subjected to history taking, clinical examination, knee US, and plain radiography. The EULAR and the OMERACT ultrasonography definitions and scanning protocols were used.

RESULTS

Fifty-three patients (44 females, 9 males) were enrolled. Mean values were 53.5 years ± 8.3 SD for age and 42.5 months ± 49.5 SD for disease duration. Crystals were detected by US in 73/106 knees (68.9%). Plain radiography revealed chondrocalcinosis in three patients. Mean values for WOMAC pain, stiffness, and disability scores were 14.38 ± 3.99, 4.93 ± 2.06, and 49.61 ± 13.06, respectively, with insignificant differences relative to presence of crystals (P > 0.05). Regression analysis revealed a 4.1-fold increase in the incidence of sonographic crystals with bursitis (OR = 4.13, CI = 1.5-11.2, p = 0.01) and a 3.2-fold increase in the incidence of sonographic crystals with synovial effusion (OR = 3.16, CI = 1.34-7.44, p = 0.01).

CONCLUSION

Subclinical crystals were detected in a considerable number of patients with primary knee OA. The incidence of crystal deposits was significantly higher in patients with bursitis and knee effusion.

The diagnostic performance of musculoskeletal ultrasound in gout: A systematic review and meta-analysis

BACKGROUND

Musculoskeletal ultrasound is widely used in diagnosing gout, but its accuracy is debatable. We conducted a systematic review and meta-analysis to quantitatively evaluate the value of ultrasound in the diagnosis of gout.

METHODS

We systematically searched for publications using Cochrane Library, PubMed/Medline and Embase and manually screened the references of eligible articles for additional relevant publications. Studies were included in this systematic review if they assessed the diagnostic accuracy of ultrasound in gout compared to that of the gold standard, demonstration of monosodium urate crystals in joint fluid or tophi. We then conducted quantitative analyses by extracting data from each study and calculating the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR) and diagnostic odds ratio (DOR). The summary receiver operating characteristic curves (sROCs) were constructed to obtain the Q*-index and the area under the curve (AUC).

RESULTS

Thirteen studies were included in this meta-analysis. The diagnostic performances of three distinctive ultrasonographic features of gout, double contour sign (DCS), the presence of tophi and the snowstorm sign, were evaluated. For person-based evaluations, the pooled sensitivity, specificity, DOR, AUC and Q* were as follows: for the DCS, 66% (95% confidence interval (CI) 62%-69%), 92% (95% CI 90%-94%), 25.91 (95% CI 11.80-56.89), 0.8163 and 0.7503, respectively; for the presence of tophi, 56% (95% CI 52%-60%), 94% (95% CI 92%-96%), 21.11 (95% CI 7.84-56.89), 0.8928 and 0.8236, respectively; for the snowstorm sign, 31% (95% CI 27%-36%), 91% (95% CI 88%-93%), 4.54(95% CI 3.13-6.58), 0.5946 and 0.5712, respectively; and for simultaneous consideration of these ultrasonographic features, 80% (95% CI 76%-83%), 83% (95% CI 79%-86%), 19.03 (95% CI 13.97-25.93), 0.889 and 0.8197, respectively. For the joint-/location-based evaluations, the pooled sensitivity, specificity, DOR, AUC and Q* were as follows: for the DCS, 75% (95% CI 68%-80%), 65% (95% CI 59%-70%), 16.90 (95% CI 5.10-56.03), 0.871 and 0.8014, respectively; and for the presence of tophi, 48% (95% CI 40%-57%), 96% (95% CI 91%-99%), 30.20 (95% CI 9.23-98.87), 0.8776 and 0.8081, respectively.

CONCLUSIONS

In this meta-analysis, relatively high specificity but modest or low sensitivity were demonstrated in the diagnosis of gout using each of the three ultrasonographic features for person-based evaluations. Simultaneous consideration of these ultrasound findings may improve the diagnostic sensitivity. However, the double contour sign alone is weak in the differentiation of gout and non-gout for joint-/location-based evaluations. Further well-designed studies are still needed to support the current findings.

Imaging tools to measure treatment response in gout

Imaging tests are in clinical use for diagnosis, assessment of disease severity and as a marker of treatment response in people with gout. Various imaging tests have differing properties for assessing the three key disease domains in gout: urate deposition (including tophus burden), joint inflammation and structural joint damage. Dual-energy CT allows measurement of urate deposition and bone damage, and ultrasonography allows assessment of all three domains. Scoring systems have been described that allow radiological quantification of disease severity and these scoring systems may play a role in assessing the response to treatment in gout. This article reviews the properties of imaging tests, describes the available scoring systems for quantification of disease severity and discusses the challenges and controversies regarding the use of imaging tools to measure treatment response in gout.

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

OBJECTIVE

This study aimed to evaluate the diagnostic performance of ultrasound (US) for patients with gout.

METHODS

We searched the Medline, Embase, Pubmed, and Cochrane Library databases, and performed a meta-analysis of the diagnostic accuracy of US according to the double contour sign, tophus, snowstorm, or bony erosion in patients with gout.

RESULTS

In total, 11 studies including 938 patients with gout, and 788 controls (patients with nongout inflammatory arthritis) were available for the meta-analysis. The pooled sensitivity and specificity of US were 65.1% ([95% confidence interval (CI): 62.0-68.2] and 89.0% (96.6-91.1), respectively. The positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were 5.889 (3.365-10.30), 0.359 (0.266-0.485), and 17.61 (11.11-17.92), respectively. The area under the curve of US was 0.858 and the Q^⁎ index was 0.789, indicating good diagnostic accuracy. Some between-study heterogeneity was found in the meta-analyses. Meta-regression showed that the sample size, study design, and diagnostic criteria were not sources of heterogeneity, and subgroup meta-analyses did not change the overall diagnostic accuracy. US signs of tophus, snowstorm, or bony erosion besides the double contour sign were not sensitive (54.3%, 30.8%, and 51.6%), but specific (93.2%, 90.6%, and 93.3%) enough as a diagnostic tool.

CONCLUSIONS

Our meta-analysis of published studies demonstrates that US offers good diagnostic accuracy with high specificity and can play an important role in the diagnosis of gout.

My Treatment Approach to Gout

Gout is the most common form of inflammatory arthritis in the United States. Nevertheless, gout remains misunderstood, misdiagnosed, underdiagnosed, and undertreated. Several new recommendation and guideline documents regarding the management of gout have been published in the past few years. New diagnostic modalities, such as ultrasound and dual-energy computed tomography, are now available. Newer treatment options exist, and older agents and their interactions are now better understood. This review addresses these recent diagnostic and therapeutic developments and describes our management protocol with the aim of providing the clinician with a pragmatic approach to gout management.

Performance of Ultrasound in the Diagnosis of Gout in a Multicenter Study: Comparison With Monosodium Urate Monohydrate Crystal Analysis as the Gold Standard

OBJECTIVE

To examine the performance of ultrasound (US) for the diagnosis of gout using the presence of monosodium urate monohydrate (MSU) crystals as the gold standard.

METHODS

We analyzed data from the Study for Updated Gout Classification Criteria (SUGAR), a large, multicenter observational cross-sectional study of consecutive subjects with at least 1 swollen joint who conceivably may have gout. All subjects underwent arthrocentesis; cases were subjects with confirmed MSU crystals. Rheumatologists or radiologists who were blinded with regard to the results of the MSU crystal analysis performed US on 1 or more clinically affected joints. US findings of interest were double contour sign, tophus, and snowstorm appearance. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Multivariable logistic regression models were used to examine factors associated with positive US results among subjects with gout.

RESULTS

US was performed in 824 subjects (416 cases and 408 controls). The sensitivity, specificity, PPV, and NPV for the presence of any 1 of the features were 76.9%, 84.3%, 83.3%, and 78.2%, respectively. Sensitivity was higher among subjects with a disease duration of ≥2 years and among subjects with subcutaneous nodules on examination (suspected tophus). Associations with a positive US finding included suspected clinical tophus (odds ratio [OR] 4.77 [95% confidence interval (95% CI) 2.23-10.21]), any abnormality on plain radiography (OR 4.68 [95% CI 2.68-8.17]), and serum urate level (OR 1.31 [95% CI 1.06-1.62]).

CONCLUSION

US features of MSU crystal deposition had high specificity and high PPV but more limited sensitivity for early gout. The specificity remained high in subjects with early disease and without clinical signs of tophi.

An optimal ultrasonographic diagnostic test for early gout: A prospective controlled study

Objective

To identify the optimal sites for classification of early gout by ultrasonography.

Methods

Sixty patients with monosodium urate crystal-proven gout (25 with early gout [≤2-year symptom duration], 35 with late gout [>2-year symptom duration], and 36 normouricemic healthy controls) from one centre were prospectively evaluated. Standardized blinded ultrasound examination of 36 joints and the triceps and patellar tendons was performed to identify tophi and the double contour (DC) sign.

Results

Ultrasonographic sensitivity was lower in early than late gout. Binary logistic regression analysis showed that two ultrasonographic signs (tophi in the first metatarsophalangeal joint [odds ratio, 16.46] and the DC sign in the ankle [odds ratio, 25.18]) significantly contributed to the final model for early gout diagnosis (sensitivity and specificity of 84% and 81%, respectively). The inter-reader reliability kappa value for the DC sign and tophi was 0.712.

Conclusions

Four-joint investigation (both first metatarsophalangeal joints for tophi and both ankles for the DC sign) is feasible and reliable and could be proposed as a screening test for early ultrasonographic gout classification in daily practice.

Value of ultrasonography in the diagnosis of gout in patients presenting with acute arthritis

OBJECTIVE

To evaluate the value of ultrasonographic features of crystal deposition for diagnosing gout in patients presenting with acute arthritis.

MATERIALS AND METHODS

Ultrasound scanning of the most inflamed joint was performed on 89 consecutively enrolled patients with acute arthritis. Two radiologists independently reviewed the ultrasound images, and a consensus was achieved with a third radiologist when the interpretations of four key ultrasound features of gout differed. Arthrocentesis and crystal analysis using compensated polarized light microscopy of aspirates are considered the gold standards for gout diagnosis.

RESULTS

Fifty-three (60%) patients had gout, whereas the remaining 36 (40%) had non-gout arthritis. The mean serum uric acid level was 7.1 mg/dl in patients with gout and 4.7 mg/dl in patients with non-gout arthritis. Three US features differed significantly (p < 0.001) between patients with gout and non-gout arthritis: the double contour sign (42 vs. 8%, respectively), intra-articular aggregates (58 vs. 8%), and tophi (40 vs. 0%). No statistically significant differences in detecting intra-tendinous aggregates (32 vs. 17%, p = 0.14) were observed. The sensitivity and specificity of the double contour sign were 42 and 92%, respectively; those of the intra-articular aggregates were 58 and 92%; and those of tophi were 40 and 100%. The positive predictive values for these three features ranged from 88 to 100%, whereas the negative predictive values ranged from 52 to 60%.

CONCLUSIONS

When the prevalence is high, these three ultrasound features may be a useful adjunct in the diagnosis of acute gout, particularly when specialized microscopic techniques are not available.

Definition and Reliability Assessment of Elementary Ultrasonographic Findings in Calcium Pyrophosphate Deposition Disease: A Study by the OMERACT Calcium Pyrophosphate Deposition Disease Ultrasound Subtask Force

OBJECTIVE

To define the ultrasonographic characteristics of calcium pyrophosphate crystal (CPP) deposits in joints and periarticular tissues and to evaluate the intra- and interobserver reliability of expert ultrasonographers in the assessment of CPP deposition disease (CPPD) according to the new definitions.

METHODS

After a systematic literature review, a Delphi survey was circulated among a group of expert ultrasonographers, who were members of the CPPD Ultrasound (US) Outcome Measures in Rheumatology (OMERACT) subtask force, to obtain definitions of the US characteristics of CPPD at the level of fibrocartilage (FC), hyaline cartilage (HC), tendon, and synovial fluid (SF). Subsequently, the reliability of US in assessing CPPD at knee and wrist levels according to the agreed definitions was tested in static images and in patients with CPPD. Cohen's κ was used for statistical analysis.

RESULTS

HC and FC of the knee yielded the highest interobserver κ values among all the structures examined, in both the Web-based (0.73 for HC and 0.58 for FC) and patient-based exercises (0.55 for the HC and 0.64 for the FC). Kappa values for the other structures were lower, ranging from 0.28 in tendons to 0.50 in SF in the static exercise and from 0.09 (proximal patellar tendon) to 0.27 (triangular FC of the wrist) in the patient-based exercise.

CONCLUSION

The new OMERACT definitions for the US identification of CPPD proved to be reliable at the level of the HC and FC of the knee. Further studies are needed to better define the US characteristics of CPPD and optimize the scanning technique in other anatomical sites.

Systematic review and quality analysis of emerging diagnostic measures for calcium pyrophosphate crystal deposition disease

OBJECTIVES

Calcium pyrophosphate crystal deposition disease (CPPD) is common, yet prevalence and overall clinical impact remain unclear. Sensitivity and specificity of CPPD reference standards (conventional crystal analysis (CCA) and radiography (CR)) were meta-analysed by EULAR (published 2011). Since then, new diagnostic modalities are emerging. Hence, we updated 2009-2016 literature findings by systematic review and evidence grading, and assessed unmet needs.

METHODS

We performed systematic search of full papers (PubMed, Scopus/EMBASE, Cochrane 2009-2016 databases). Search terms included CPPD, chondrocalcinosis, pseudogout, ultrasound, MRI, dual energy CT (DECT). Paper selection, data abstraction, EULAR evidence level, and Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 bias and applicability grading were performed independently by 3 authors.

RESULTS

We included 26 of 111 eligible papers, which showed emergence in CPPD diagnosis of ultrasound (U/S), and to lesser degree, DECT and Raman spectroscopy. U/S detected CPPD crystals in peripheral joints with sensitivity >80%, superior to CR. However, most study designs, though analytical, yielded low EULAR evidence level. DECT was marginally explored for CPPD, compared with 35 published DECT studies in gout. QUADAS-2 grading indicated strong applicability of U/S, DECT and Raman spectroscopy, but high study bias risk (in ∼30% of papers) due to non-controlled designs, and non-randomised subject selection.

CONCLUSIONS

Though CCA and CR remain reference standards for CPPD diagnosis, U/S, DECT and Raman spectroscopy are emerging U/S sensitivity appears to be superior to CR. We identified major unmet needs, including for randomised, blinded, controlled studies of CPPD diagnostic performance and rigorous analyses of 4 T MRI and other emerging modalities.

Imaging in Gout and Other Crystal-Related Arthropathies

In this article, the authors consider the manifestations of intraarticular and periarticular crystal deposits. Most cases of crystal deposits are asymptomatic and represent incidental findings at imaging. In symptomatic arthropathies, imaging can play an important role in the diagnosis and assessment of disease progression and the extent of crystal deposits. Conventional radiography is the most common imaging modality. But ultrasound, conventional computerized tomography (CT), dual-energy CT, and MRI play an increasing role. The authors review typical radiographic features of crystal-induced arthropathies and findings that help to differentiate them. The authors also emphasize the increasing role of complementary imaging techniques.

Performance of the Existing Classification Criteria for Gout in Thai Patients Presenting With Acute Arthritis

Currently, there are 5 existing classification criteria for gout: the Rome, New York, American Rheumatism Association (ARA), Mexico, and Netherlands criteria. This study was carried out to determine the performance of these classification criteria in Thai patients presenting with acute arthritis.All consecutive patients presenting with acute arthritis and being consulted at the Rheumatology Unit, Chiang Mai University Hospital from January 2013 to May 2015 were invited to join the study. Gout was defined by the presence of monosodium urate crystals in the synovial fluid or tissue examined by experienced rheumatologists. The 5 existing gout classification criteria were performed and evaluated in all of the patients, who were divided in subgroups of early disease (≤2 years), established disease (>2 years), and those without tophus.There were 136 gout and 97 nongout patients. Sensitivity and specificity across all criteria ranged from 75.7% to 97.1% and 68.0% to 84.5%, respectively. Overall, the Mexico criteria had the highest sensitivity (97.1%), and the ARA survey criteria the highest specificity (84.5%), whereas the Mexico criteria performed well in early disease with sensitivity and specificity of 97.1% and 81.7%, respectively. All 5 criteria showed high sensitivity (from 76.4% to 99.1%) but low specificity (from 30.8% to 65.4%) in established disease. In patients without tophus, the sensitivity and specificity ranged from 64.1% to 95.7% and 68.8% to 85.4%, respectively. The ARA survey criteria across all groups showed consistently high specificity for gout.The 5 existing classification criteria for gout had limited sensitivity and specificity in Thai patients presenting with acute arthritis. The ARA survey criteria are the most suitable for diagnosing gout in Thai people when crystal identification is not available.