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

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.

The value of musculoskeletal ultrasound in predicting gout flares in index joints: A prospective cohort study of people with gout starting urate-lowering therapy

OBJECTIVES

To evaluate whether ultrasound findings of monosodium urate (MSU) crystal deposition predict frequent gout flares in index joints over 12 months.

METHODS

This single-center study enrolled people with at least one gout flare involving the MTP1, ankle or knee joint. The most painful or most frequently joint was identified as index joint for analysis. All participants were started on urate-lowering therapy and had an ultrasound scan of the index joints at the baseline visit. OMERACT scores (for tophus, double contour sign and aggregates) were used to analyze whether ultrasound scores predicted frequent (≥2) gout flares in the index joint over 12 months.

RESULTS

Frequent flares were significantly higher in those with ultrasound findings in all index joints (MTP1: tophus: 85.0% vs 46.0%, P < 0.001, aggregates: 78.8% vs 59.0%, P < 0.01; ankle: tophus: 54.6% vs 20.8%, P < 0.001; aggregates: 60.0% vs 35.9%, P < 0.05; knee: tophus: 68.4% vs 28.6%, P < 0.05). For the MTP1, for each 1-point increase in tophus score, the odds of frequent gout flares increased by 5.19 [(95%CI: 1.26-21.41), 7.91 [(95%CI: 2.23-28.14), and 13.79 [(95%CI: 3.79-50.20)] fold respectively. For the ankle, a tophus score of 3 markedly improved the prediction of the frequent flares [OR= 9.24 (95%CI=2.85-29.91)]. Semi-quantitative sum scores were associated with frequent flares with an OR (95%CI) of 13.66 (3.44-54.18), P < 0.001 at the MTP1, 7.05 (1.98-25.12), P < 0.001 at the ankle.

CONCLUSION

Ultrasound features of MSU crystal deposition at the MTP1 and knee predict subsequent risk of frequent gout flares in the same joints following initiation of urate-lowering therapy, with the highest risk in those with high tophus scores.

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.

Gout Remission as a Goal of Urate-Lowering Therapy: A Critical Review

Urate-lowering therapies for the management of gout lead to a reduction in serum urate levels, monosodium urate crystal deposition, and the clinical features of gout, including painful and disabling gout flares, chronic gouty arthritis, and tophi. Thus, disease remission is a potential goal of urate-lowering therapy. In 2016, preliminary gout remission criteria were developed by a large group of rheumatologists and researchers with expertise in gout. The preliminary gout remission criteria were defined as: serum urate < 0.36 mmol/L (6 mg/dL); an absence of gout flares; an absence of tophi; pain due to gout < 2 on a 0-10 scale; and a patient global assessment < 2 on a 0-10 scale over a 12-month period. In this critical review, we describe the development of the preliminary gout remission criteria, the properties of the preliminary gout remission criteria, and clinical studies of gout remission in people taking urate-lowering therapy. We also describe a future research agenda for gout remission.

Dynamic assessment of the double contour sign by ultrasonography helps to distinguish between gout and calcium pyrophosphate deposition disease

OBJECTIVE

To test whether the double contour (DC) sign has a different dynamic behaviour in gout and calcium pyrophosphate deposition (CPPD) and whether the dynamic assessment of the DC sign increases its accuracy in gout diagnosis.

METHODS

This cross-sectional analysis included patients with gout meeting the 2015 ACR/EULAR classification criteria and patients with crystal-proven diagnosis of CPPD. Hyaline cartilages were explored by ultrasound (US) to detect the DC sign (ie, abnormal hyperechoic band over the superficial margin of hyaline cartilages) and its dynamic behaviour during joint movement was evaluated ((ie, movement of the DC sign together with subchondral bone (DC sign), or in the opposite direction (pseudo DC sign)).

RESULTS

Eighty-one patients with gout and 84 patients with CPPD underwent US assessment. Among them, 47 patients with gout and 9 patients with CPPD had evidence of the DC sign. During dynamic assessment, in all 47/47 patients with gout there was a DC sign. Conversely, in 7/9 (77.8%) patients with CPPD, there was a pseudo DC sign (p<0.01).The presence of DC sign during static assessment had a sensitivity, specificity and accuracy of 58.0% (95% CI 46.5% to 68.9%), 89.3% (95% CI 80.6% to 95.0%) and 73.9% (95% CI 66.5% to 80.5%) for gout, respectively. The dynamic evaluation improved the DC sign's diagnostic performance (p=0.01) as the specificity (97.6% (95% CI 91.7% to 99.7%)) and the accuracy (78.2% (95% CI 71.1% to 84.2%)) increased without loss in sensitivity.

CONCLUSION

The dynamic US assessment of the DC sign may help to differentiate the DC sign due to MSU crystals from the pseudo DC sign seen in CPPD, as they move in opposite directions.

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.

Sonographic Tophi and Inflammation Are Associated With Carotid Atheroma Plaques in Gout

Objective: Gout and cardiovascular disease are closely related, but the mechanism connecting them remains unknown. This study aims to explore whether urate crystal deposits and inflammation (assessed by ultrasound) are associated with carotid atherosclerosis.

Methods: We included consecutive patients with crystal-proven gout newly presenting to a tertiary rheumatology unit. Patients under urate-lowering treatment were excluded. Ultrasound assessment was performed during intercritical periods. Musculoskeletal scans evaluated six joints and four tendons for urate crystal deposits (double contour, aggregates, and tophi), and power Doppler (PD) signal (graded 0–3) as a marker of local inflammation. The sum of locations showing deposits or a positive PD signal (≥1) was registered. Carotids were scanned for increased intima-media thickness (IMT) and atheroma plaques, according to the Mannheim consensus. Associations were analyzed using logistic regression.

Results: The study included 103 patients showing sonographic crystal deposits at the examined locations (mean sum 9.9, minimum 2); tophi were the most frequent. Two-thirds of participants presented a positive PD signal (30.1% grade 2–3). In the carotid scans, 59.2% of participants showed atheroma plaques, and 33.0% increased IMT. Tophi (odds ratio [OR] 1.24; 95% confidence interval [CI] 1.03–1.50) and a positive PD signal (OR 1.67; 95% CI 1.09–2.56) were significantly associated with atheroma plaques, while an increased IMT showed no sonographic association.

Conclusion: Sonographic crystal deposits and subclinical inflammation were consistently observed in patients with intercritical gout. Tophi and a positive PD signal were linked to carotid atherosclerosis. Our findings may contribute to understanding the complex relationship between gout and atherosclerosis.

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.