Ultrasonography and dual-energy computed tomography provide different quantification of urate burden in gout: results from a cross-sectional study

Associations of Changes in Knee Hyaline Cartilage Composition Measured With Dual-Energy Computed Tomography in Gout, Aging and Osteoarthritis

OBJECTIVE

To characterize dual-energy computed tomography (DECT) changes depicting hyaline cartilage changes in gout patients with and without osteoarthritis (OA) and in comparators without gout.

DESIGN

Patients with suspected crystal-associated arthropathy were enrolled and underwent bilateral DECT scans of the knees. Standardized regions of interest were defined in the femorotibial hyaline cartilage. Five DECT parameters were obtained: CT numbers in Hounsfield units (HU) at 80 and 140 kV, the electron density (Rho), the effective atomic number (Zeff), and the dual-energy index (DEI). Zones were compared between patients with gout, with and without knee OA, and between patients with gout and comparators without gout, after adjustment for confounders.

RESULTS

A total of 113 patients with gout (mean age 63.5 ± 14.3 years) and 15 comparators without gout (mean age 75.8 ± 11.5 years) were included, n = 65 (51%) had knee OA, and 466 zones of hyaline cartilage were analyzed. Older age was associated with lower attenuations at 80 kV (P < 0.01) and 140 kV (P < 0.01), and with Rho (P < 0.01). OA was characterized by lower attenuation at 140 kV (P = 0.03), but the lower Rho was nonsignificant after adjustment for confounders. In gout, hyaline cartilage exhibited lower Rho values (adjusted P = 0.04). Multivariable coefficients of association with Rho were -0.21 [-0.38;-0.04] (P = 0.014) for age, -4.15 [-9.0;0.7] (P = 0.093) for OA and 0.73 [-0.1;1.56] (P = 0.085) for monosodium urate volume.

CONCLUSION

Gout was associated with DECT-detected changes in cartilage composition, similar to those observed in older patients, with some similarities and some differences to those seen in OA. These results suggest the possibility of potential DECT biomarkers of OA.

Correlations of characteristics with tissue involvement in knee gouty arthritis: Magnetic resonance imaging analysis

Objective

This study investigates the MRI features of knee gouty arthritis (KGA), examines its relationship with the extent of tissue involvement, and assesses whether risk factors can predict KGA.

Materials and methods

Patients diagnosed with KGA underwent MRI examinations, and two independent observers retrospectively analyzed data from 44 patients (49 knees). These patients were divided into mild and severe groups based on tissue involvement observed during arthroscopy. MRI features were summarized, and the intraclass correlation coefficient evaluated interobserver reproducibility. Single-factor analysis compared clinical indicators and MRI features between groups, while Cramer's V coefficient assessed correlations. Multivariate logistic regression identified predictors of tissue involvement extent, and a ROC curve evaluated diagnostic performance.

Results

Among 49 knees, 18 had mild and 31 had severe tissue involvement. Key MRI features included ligament sketch-like changes, meniscal urate deposition, irregularly serrated cartilage changes, low-signal signs within joint effusion, synovial proliferation, Hoffa's fat pad synovitis, gouty tophi, bone erosion, and bone marrow edema. The interobserver reliability of the MRI features was good. Significant differences (P < 0.05) were observed between the groups for anterior cruciate ligament (ACL) sketch-like changes, Hoffa's fat pad synovitis, and gouty tophi. ACL sketch-like changes (r = 0.309), Hoffa's fat pad synovitis (r = 0.309), and gouty tophi (r = 0.408) were positively correlated with the extent of tissue involvement (P < 0.05). ACL sketch-like changes (OR = 9.019, 95 % CI: 1.364-61.880), Hoffa's fat pad synovitis (OR = 6.472, 95 % CI: 1.041-40.229), and gouty tophi (OR = 5.972, 95 % CI: 1.218-29.276) were identified as independent predictors of tissue involvement extent (P < 0.05). The area under the ROC curve was 0.862, with a sensitivity of 67.70 %, specificity of 94.40 %, and accuracy of 79.14 %.

Conclusion

This comprehensive analysis of MRI features identifies ligament sketch-like changes, meniscal urate deposition, and low-signal signs within joint effusion as characteristic MRI manifestations of KGA. Irregular cartilage changes are valuable for differential diagnosis in young and middle-aged patients. ACL sketch-like changes, Hoffa's fat pad synovitis, and gouty tophi correlate with tissue involvement severity and are critical in predicting and assessing the extent of tissue involvement in KGA.

Prediction of renal and cardiometabolic outcomes in gout during urate-lowering therapy by sonography

OBJECTIVES

To assess whether the extent of monosodium urate (MSU) crystal deposition estimated by ultrasound could predict renal and cardiometabolic events during urate-lowering therapy (ULT).

METHODS

A prospective study on gout patients from two referral centers initiating ULT who underwent baseline ultrasound and were followed for 1 year. Ultrasound scans assessed six joints for double-contour (DC) signs and tophi. A five-point change (mL/min/1.73 m2 ) in the glomerular filtration rate at month 12 (M12) was considered significant. Outcomes of interest were renal function degraded versus improved and a composite cardiometabolic outcome (new hypertension, diabetes, atherosclerotic disease, and cardiovascular death). Homogeneity analyses and Cox regression models were performed.

RESULTS

One hundred sixty patients were recruited. At baseline, 81.1% of patients (n = 129) showed sonographic tophi with a mean number of 1.4 joints (±1.3) with a DC sign. At M12, 18 patients (11.3%) were lost to follow-up. The serum urate (SU) target (<6.0 mg/dL) was reached in 86 patients (69.9%). Regarding renal function, 15.9% of patients showed improvement, while in 31.0% it degraded. Fourteen new cardiometabolic events occurred in 12 patients. Neither the DC sign nor tophi showed any significant impact on the outcomes of interest. Baseline SU level was higher in those with renal improvement but not with renal decline, while achieving the SU target protected against new cardiometabolic events (HR = 0.2; 95% CI: 0.05-0.81).

CONCLUSIONS

Sonographic MSU crystal burden was unhelpful in predicting renal and cardiometabolic events during the first year of ULT. Reaching the SU target prevented cardiometabolic events, while its benefit in preserving/improving renal function is unclear.

Factors influencing the kinetics of MSU crystal depletion measured with dual-energy CT in patients with gout

OBJECTIVE

To examine factors influencing the kinetics of monosodium urate (MSU) crystal dissolution measured with dual-energy computed tomography (DECT) during follow-up of patients with gout.

METHODS

Patients with a diagnosis of gout with baseline knees and feet DECT scans exhibiting MSU crystal volumes ≥0.1 cm3 and at least one follow-up DECT were included. Spearman's correlation coefficient was used to search for association between change from baseline MSU crystal volume at 6, 12, 18 and 24 months and serum urate (SU) level. Associations between percentage change from the baseline volume of MSU crystal deposits and explanatory variables were assessed using linear mixed models.

RESULTS

Sixty-two patients (age 67.3±12.8 years; 53 (85%) males) cumulating 104 follow-up DECT scans were included. Overall, SU target levels (<6.0 and <5.0 mg/dL) were achieved by 48 (77%) and 36 (58%) patients, respectively. There was a good correlation (r=0.66; p<0.0001) observed between SU level and percentage change in MSU crystal volume. The median decrease from baseline MSU crystal volume was greater in patients reaching the <5.0 mg/dL SU target than in those reaching ≥5.0 SU <6.0 mg/dL: -85% (95% CI: -94% to -72%) versus -40% (-57% to -22%; p<0.05) at 12 months. In multivariable analysis, time (in days) with a multilevel coefficient of -0.06 (95% CI: -0.08 to -0.03, p<0.001), hypertension (coefficient: 41.87, 95% CI: 16.38 to 67.18, p<0.01) and SU level <5.0 mg/dL (coefficient: -39.46, 95% CI: -70.93 to -8.34, p=0.02) were the only variables significantly associated with MSU crystal volume change.

CONCLUSION

In patients with DECT-measured MSU crystal deposition, reaching the <5.0 mg/dL SU target provides more extensive and rapid crystal dissolution than reaching the <6.0 mg/dL SU target.

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.

Dual-energy computed tomography in crystalline arthritis: knowns and unknowns

PURPOSE OF REVIEW

To give an overview of what can reasonably be considered as known about dual-energy computed tomography (DECT) in crystal-related arthropathies, and what still needs to be explored.

RECENT FINDINGS

Recent studies suggest an overall superiority of DECT over ultrasound in gout in terms of sensitivity (89 vs. 84%) and specificity (91 vs. 84%), except in early disease. Additional studies are needed to optimize DECT postprocessing settings in order to improve the specificity of the technique and eliminate all artifacts. Evidence has been controversial concerning DECT's ability to detect monosodium urate (MSU) crystal deposits on vessel walls, or whether or not MSU-coded plaques are artifacts. DECT can be used to monitor MSU crystal depletion during urate-lowering treatment; MSU crystal volume is associated with cardiovascular risk and disease activity. There are some reports on calcium-containing crystal deposition diseases (calcium pyrophosphate and basic calcium phosphate) demonstrating that DECT can characterize and discriminate between the different types of crystals.

SUMMARY

Our knowledge about the use of DECT in crystal-related arthropathies continues to expand. Some unknowns have been clarified but there's still lots to learn, particularly concerning gout management and the potential use of DECT in calcium-containing crystal-related arthropathies.

The Role of Advanced Imaging in Gout Management

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

Optimization of dual energy computed tomography post-processing to reduce lower limb artifacts in gout

BACKGROUND

In gout, several types of dual-energy computed tomography (DECT) artifacts have been described (nail bed, skin, beam hardening, submillimeter and vascular artifacts), which can lead to overdiagnosis. The objective of this study was to determine the optimal DECT settings for post processing in order to reduce the frequency of some common artifacts in patients with suspected gout.

METHODS

Seventy-seven patients hospitalized for suspected gout (feet/ankles and/or knees) who received a DECT imaging were included (final diagnosis of 43 gout and 34 other rheumatic disorders). Different post-processing settings were evaluated using Syngovia software: nine settings (R1 to R9) were evaluated with a combination of different ratio (1.28, 1.36 and 1.55) and attenuation coefficient (120, 150, 170 HU).

RESULTS

Among the nine settings tested, the R2 setting (170 HU, ratio =1.28) significantly reduced the presence of knee and foot/ankle artifacts compared to the standard R1 setting (85% and 94% decrease in beam hardening and clumpy artifacts in the ankle and foot, respectively (P<0.001); a decrease of 71%, 60% and 88% respectively of meniscal beam hardening, beam hardening and submillimeter artifacts in the knee (P<0.001). Compared to standard settings, the use of R2 settings decreased sensitivity [0.79 (95% CI: 0.65, 0.88) versus 0.90 (95% CI: 0.78, 0.96)] and increased specificity [0.86 (95% CI: 0.71, 0.93) versus 0.63 (95% CI: 0.47, 0.77)] (P<0.001). Settings using an attenuation coefficient to 120 HU and/or a ratio to 1.55 were all associated with a significant increasing of artifacts, especially clumpy and beam hardening artifacts.

CONCLUSIONS

Applying a ratio of 1.28 and a minimum attenuation of 170 HU in DECT post-processing eliminates the majority of artifacts located in the lower limbs, particularly clumpy artifacts and beam hardening.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

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.

Entheseal involvement of the lower extremities in gout: an ultrasonographic descriptive observational study

OBJECTIVE

The aim of this study was to explore the prevalence and distribution of lower extremity entheseal abnormities by musculoskeletal ultrasound (US) in a cohort of gout patients, taking spondyloarthritis (SpA) patients and asymptomatic hyperuricemia (HUA) patients as controls.

METHOD

One hundred participants with gout, fifty patients with SpA, and twenty-nine patients with asymptomatic HUA were recruited. US was used to assess the bilateral quadriceps, patellar and Achilles tendons, and plantar fascia entheses according to the Outcome Measures in Rheumatology (OMERACT) definitions.

RESULTS

The US examination revealed the presence of one or more abnormalities in at least one enthesis in 45 out of 100 subjects (45.0%) and 152 out of 1000 entheses (15.2%) in the gout patients. Among the affected entheses, the patellar insertion of the quadriceps tendon was the most commonly involved area (38.0% in the gout patients versus 48.0% in the SpA patients with at least one pathological US finding, p = 0.241). There were no significant group differences in entheseal power Doppler (PD) signals, bone erosion, or enthesophytes. The patients with lower limb entheseal involvement in the gout group had an older age, longer disease duration, higher percentage of chronic tophaceous gout, and higher levels of inflammatory biomarkers of the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Multivariate logistic regression analysis revealed that age (OR = 1.052, p = 0.001) and the ESR (OR = 1.023, p = 0.028) were correlated with lower limb enthesopathy in gout patients. In the subgroup analysis of gout patients without active inflammation, age (OR = 1.119, p = 0.001) and serum uric acid (UA, OR = 1.012, p = 0.002) were correlated with lower limb enthesopathy in gout.

CONCLUSION

Lower extremity entheseal involvement might be neglected but should be considered as an important element in the evaluation of gout patients. Enthesopathy most frequently involves in the patellar insertion of the quadriceps tendon and is characterized by entheseal hypoechogenicity and/or thickening. Key Points • Lower extremity enthesopathy might be neglected as an important element in gout. • Enthesopathy is most frequently involved in the patellar insertion of the quadriceps tendon in gout. • Age and ESR are correlated with lower limb enthesopathy in gout patients.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Gouty Involvement of Foot and Ankle: Beyond Flares

The foot and ankle are common locations of deposition of monosodium urate (MSU) crystals, as indicated by the clinical manifestations presented by patients with gout, which are not limited to the acute inflammation of the big toe. We present a narrative literature review aimed to update the gout involvement of foot and ankle and how it affects the quality of life. Cumulative reports indicate that gout, even at the non-tophaceous stage, could cause pain, gait impairment and limit the mobility at lower limbs. These patients may present difficulties in some activities of daily living such as choosing footwear, thus leading to an impaired quality of life. Gout is a curable disease by dissolving MSU crystals but remains unclear how this could modify some of these foot and ankle manifestations, especially when structural damage has already occurred. Furthermore, a collaboration between rheumatologists and podiatrists seems helpful to understand, relieve these symptoms and improve the quality of life in gouty patients.

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

Objectives

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

Methods

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

Results

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

Conclusions

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

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

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

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

METHODS

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

RESULTS

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

CONCLUSION

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

External validation of Gout-calculator performance on a cohort of acute arthritis (SYNOLACTATE) sparing distal joints such as hallux and midfoot. A cross-sectional study of 170 patients

OBJECTIVE

To evaluate the performance of the Gout-calculator in a cohort of consecutive acute arthritis affecting large and intermediate joints (without an attack on hallux or midfoot joints).

METHODS

A retrospective study. Gout-calculator data were collected in medical records of patients included in the prospective consecutive cohort of acute arthritis called SYNOLACTATE. The diagnosis of gout was defined by the presence of sodium urate crystals in synovial fluid. The diagnostic performance of the Gout-calculator was studied by performing an ROC curve with the calculation of its AUC (95% CI) as well as the calculation of Sensitivity (Se), Specificity (Sp), and positive likelihood ratio (LR+).

RESULTS

170 patients with acute arthritis were included. Variables associated with the diagnosis of gout were as follows: serum uric acid > 350 μmol/L (OR 5.52 (2.52-12.1), p < 0.001), joint redness (OR 5.08 (1.85-14.0), p = 0.001), previous patient-reported arthritis attack (OR 4.04 (1.92-8.49), p < 0.001), male (OR 3.00 (1.17-7.69), p = 0.02), hypertension or cardiovascular disease (OR 2.33 (1.07-5.06), p = 0.03). The median (IQR) of Gout-calculator was significantly higher in gouty arthritis (7.0 [5.5-8.1]) than in associated-CPP acute arthritis (4.0 [2.0-5.8]), septic arthritis (3.0 [2.0-5.1]), or others arthritis (3.5 [2.0-5.5]). The AUC was 0.833 (0.768-0.897) with for the threshold ≥ 8, a Se at 27.5% (0.161-0.428), Sp 97.7% (0.934-0.992), and LR+ 11.9 (3.5-40).

CONCLUSION

Despite diagnostic performances close to those published, the use of the Gout-calculator is not sufficient for the diagnosis of gout or to exclude the differential diagnosis of septic arthritis in the SYNOLACTATE cohort.

KEY POINTS

• For a Gout-calculator threshold of ≤ 4, Sensitivity is 92.5%, Specificity 50.8% and LR- 0.15 to the gout diagnosis. • For a Gout-calculator threshold of > = 8, Sensitivity is 27.5%, Specificity 97.7% and LR+ 11.9 to the gout diagnosis. • In a population of acute arthritis affecting large joints, Gout-calculator is not sufficient to discriminate between gouty arthritis and septic arthritis.

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.

Imaging of crystalline arthropathy in 2020

Crystal-related arthropathies are the result of crystal deposition in joint and periarticular soft tissues. Identification of urate crystals is mandatory to distinguish gout from other crystalline arthropathies, including calcium pyrophosphate dihydrate and basic calcium phosphate crystal deposition diseases. ACR/EULAR classification criteria for gout included dual-energy computed tomography and ultrasound with equal impact to the final score. Different diagnostic strengths of these imaging modalities depend on disease duration and scanned anatomic site. While ultrasound has been indicated as the first-choice imaging technique, especially in the early stages of the disease, dual-energy computed tomography has shown to be highly specific, allowing the detection of crystal deposits in anatomic sites not accessible by ultrasound, such as the spine. At the spinal level, MRI findings are usually nonspecific. Finally, there is preliminary evidence that at the knee, dual-energy computed tomography may discriminate calcium pyrophosphate dihydrate from basic calcium phosphate crystal deposits.

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.

Dual-energy computed-tomography-based discrimination between basic calcium phosphate and calcium pyrophosphate crystal deposition in vivo

Background:

Dual-energy computed tomography (DECT) is being considered as a non-invasive diagnostic and characterization tool in calcium crystal-associated arthropathies. Our objective was to assess the potential of DECT in distinguishing between basic calcium phosphate (BCP) and calcium pyrophosphate (CPP) crystal deposition in and around joints in vivo.

Methods:

A total of 13 patients with calcific periarthritis and 11 patients with crystal-proven CPPD were recruited prospectively to undergo DECT scans. Samples harvested from BCP and CPP calcification types were analyzed using Raman spectroscopy and validated against synthetic crystals. Regions of interest were placed in BCP and CPP calcifications, and the following DECT attenuation parameters were obtained: CT numbers (HU) at 80 and 140 kV, dual-energy index (DEI), electron density (Rho), and effective atomic number (Z_eff). These DECT attenuation parameters were compared and validated against crystal calibration phantoms at two known equal concentrations. Receiver operating characteristic (ROC) curves were plotted to determine the highest accuracy thresholds for DEI and Z_eff.

Results:

Raman spectroscopy enabled chemical fingerprinting of BCP and CPP crystals both in vitro and in vivo. DECT was able to distinguish between HA and CPP in crystal calibration phantoms at two known equal concentrations, most notably by DEI (200 mg/cm³: 0.037 ± 0 versus 0.034 ± 0, p = 0.008) and Z_eff (200 mg /cm³: 9.4 ± 0 versus 9.3 ± 0, p = 0.01) analysis. Likewise, BCP calcifications had significantly higher DEI (0.041 ± 0.005 versus 0.034 ± 0.005, p = 0.008) and Z_eff (9.5 ± 0.2 versus 9.3 ± 0.2, p = 0.03) than CPP crystal deposits with comparable CT numbers in patients. With an area under the ROC curve of 0.83 [best threshold value = 0.0 39, sensitivity = 90. 9% (81.8, 97. 7%), specificity = 64.6% (50.0, 64. 6%)], DEI was the best parameter in distinguishing between BCP and CPP crystal depositions.

Conclusion:

DECT can help distinguish between crystal-proven BCP and CPP calcification types in vivo and, thus, aid in the diagnosis of challenging clinical cases, and in the characterization of CPP and BCP crystal deposition occurring in osteoarthritis.

Association of Specific Comorbidities with Monosodium Urate Crystal Deposition in Urate-Lowering Therapy-Naive Gout Patients: A Cross-Sectional Dual-Energy Computed Tomography Study

(1) Background: To determine which factors are associated with the volume of monosodium urate (MSU) crystal deposition quantified by dual-energy computed tomography (DECT) in urate-lowering therapy (ULT)-naive gout patients. (2) Methods: In this multicenter cross-sectional study, DECT scans of knees and feet/ankles were prospectively obtained from ULT-naive gout patients. Demographic, clinical (including gout history and comorbidities), and biological data were collected, and their association with DECT MSU crystal volume was analyzed using bivariate and multivariate analyses. A second bivariate analysis was performed by splitting the dataset depending on an arbitrary threshold of DECT MSU volume (1 cm³). (3) Results: A total of 91 patients were included. In the bivariate analysis, age (p = 0.03), gout duration (p = 0.003), subcutaneous tophi (p = 0.004), hypertension (p = 0.02), diabetes mellitus (p = 0.05), and chronic heart failure (p = 0.03) were associated with the total DECT volume of MSU crystal deposition. In the multivariate analysis, factors associated with DECT MSU volumes ≥1 cm³ were gout duration (odds ratio (OR) for each 10-year increase 3.15 (1.60; 7.63)), diabetes mellitus (OR 4.75 (1.58; 15.63)), and chronic heart failure (OR 7.82 (2.29; 31.38)). (4) Conclusion: Specific comorbidities, particularly chronic heart failure and diabetes mellitus, are more strongly associated with increased MSU crystal deposition in knees and feet/ankles than gout duration, regardless of serum urate level.

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.

Impact of Dual-Energy CT Postprocessing Protocol for the Detection of Gouty Arthritis and Quantification of Tophi in Patients Presenting With Podagra: Comparison With Ultrasound

OBJECTIVE. The objective of our study was to compare ultrasound (US) tophus and monosodium urate (MSU) deposit detection and US tophus size in the metatarsophalangeal (MTP) 1 joint with dual-energy CT (DECT) using two DECT postprocessing protocols in patients presenting with podagra. SUBJECTS AND METHODS. Seventy-five consecutive patients with podagra (66 men and nine women; mean age, 65.6 years; age range, 33-88 years) and 75 control subjects with MTP 1 joint osteoarthritis (49 men and 26 women; mean age, 63.0 years; age range, 35-87 years) prospectively underwent US and DECT between 2016 and 2018 to assess the MTP 1 joint. Two Syngovia postprocessing DECT protocols with different minimum attenuation thresholds of 150 HU (DECT 150 protocol) versus 120 HU (DECT 120 protocol) and the same maximum attenuation threshold (500 HU) and constant kilovoltage setting of tubes A and B at 80 and 140 kVp were evaluated. Interobserver variability of the two DECT protocols was calculated and compared with that of US. RESULTS. The postprocessing DECT 150 protocol was positive for tophus detection in 55 of 75 patients (73.3%) with podagra, whereas the postprocessing DECT 120 protocol detected MSU deposits in all 75 patients (100%). Tophus size assessed using the DECT 120 protocol showed an improved correlation with tophus size detected on US (p < 0.01). Interobserver variability of DECT was improved when using the DECT 120 protocol (p < 0.01). CONCLUSION. The postprocessing DECT 120 protocol enables improved visualization of MSU deposits and provides more accurate information about tophus size that better correlates with tophus size on US compared with the standard postprocessing DECT 150 protocol.

Dual-energy computed tomography in calcium pyrophosphate deposition: initial clinical experience

OBJECTIVE

To determine the dual-energy computed tomography (DECT) attenuation properties of meniscal calcifications in calcium pyrophosphate deposition (CPPD) in vivo, and assess whether DECT was able to discriminate meniscal CPP deposits from calcium hydroxyapatite (HA) in subchondral and trabecular bone.

METHOD

Patients with clinical suspicion of crystal-related arthropathy (gout and/or CPPD) and knee DECT scans were retrospectively assigned to CPPD (n = 19) or control (n = 21) groups depending on the presence/absence of chondrocalcinosis on DECT. Two observers drew standardized regions of interest (ROI) in meniscal calcifications, non-calcified menisci, as well as subchondral and trabecular bone. Five DECT parameters were obtained: CT numbers (HU) at 80 and 140 kV, dual-energy index (DEI), electron density (ρ_e), and effective atomic number (Z_eff). The four different knee structures were compared within/between patients and controls using linear mixed models, adjusting for confounders.

RESULTS

Meniscal calcifications (n = 89) in CPPD patients had mean ± SD CT numbers at 80 and 140 kV of 257 ± 64 and 201 ± 48 HU, respectively; with a DEI of 0.023 ± 0.007, and ρ_e and Z_eff of 140 ± 35 and 8.8 ± 0.3, respectively. Meniscal CPP deposits were readily distinguished from calcium HA in subchondral and trabecular bone (p ≤ 0.001), except at 80 kV separately (p = 0.74). Z_eff and ρ_e both significantly differed between CPP deposits and calcium HA in subchondral and trabecular bone (p < 0.0001).

CONCLUSION

This proof-of-concept study shows that DECT has the potential to discriminate meniscal CPP deposits from calcium HA in subchondral and trabecular bone in vivo, paving the way for the non-invasive biochemical signature assessment of intra- and juxta-articular calcium crystal deposits.

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

Background

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

Methods

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

Results

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

Conclusions

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

Electronic supplementary material

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

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

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

Detection of uric acid crystal deposition by ultrasonography and dual-energy computed tomography: A cross-sectional study in patients with clinically diagnosed gout

The aim of our study was to compare the performance of ultrasonography (US) and dual-energy computed tomography (DECT) in detecting the crystal deposition at lower extremity joints in patients with gout. The correlation of imaging findings with microscopic findings was further assessed whenever aspiration is available.We recruited consecutive patients who were presented with arthritis of lower extremity from January 2012 to December 2014. All the patients underwent DECT and US scan of bilateral knees, ankles, and feet. Synovial fluid was obtained by aspiration from an acute inflammatory joint if possible.Finally, 60 patients fulfilling the 1977 gout classification criteria were included in our study. We found that US can detect significantly more patients with crystal deposition than DECT (81.7% vs 56.7%, by US and DECT, respectively, P < .001). The frequency of urate crystal deposition detected by US at MTP1, knee, and ankle joints regions was 56.7%, 63.3%, and 51.7%, respectively. The percentage of positivity of double contour sign on US was 33.3%, 48.3%, and 41.7% at the joints mentioned above, respectively. There was a good correlation between ultrasound and synovial fluid analysis in detecting crystal deposition (κ = 0.87, P = .001), while the agreement between DECT and synovial fluid analysis was just fair (κ = 0.28, P = .02).The sensitivity of US in detecting urate crystal deposition in lower extremity joints was higher than DECT. The superiority was more obvious in knee and MTP1 joints. US should be considered as the first choice of image examinations when diagnosing gout.

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

Background

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

Methods

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

Results

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

Conclusions

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

Electronic supplementary material

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

The lack of association between the burden of monosodium urate crystals assessed with dual-energy computed tomography or ultrasonography with cardiovascular risk in the commonly high-risk gout patient

Background

Gout is associated with higher cardiovascular risk that increases with disease severity. The objective of this study was to explore the relationship between the extent of monosodium urate (MSU) crystal deposition, assessed with ultrasonography (US) and dual-energy computed tomography (DECT), and cardiovascular risk.

Methods

Gout patients were included in this cross-sectional study to undergo DECT scans for the assessment of total MSU volume deposition in the knees and feet, and US to evaluate the number of joints with the double contour (DC) sign. Participants were screened for traditional cardiovascular risk factors, and levels of the American College of Cardiology (ACC)/American Heart Association (AHA) 10-year risk for heart disease or stroke were calculated. The primary endpoint was the Spearman correlation coefficient ρ between DECT MSU volume and cardiovascular risk.

Results

A total of 42 patients were included; they were predominantly male (40/42) and aged 63.0 ± 13.2 years. Overall, 28/42 patients presented with the metabolic syndrome and the average 10-year coronary event or stroke risk according to the ACC/AHA (n = 33) was 21 ± 15%. Correlations between DECT volumes of MSU deposits in the knees, feet, and knees + feet and cardiovascular risk according to the ACC/AHA were very poor, with ρ = 0.18, −0.01, and 0.13, respectively. The was no correlation between the number of joints with the DC sign and cardiovascular risk (ρ = −0.07). DECT MSU deposit volume was similar in patients with and without metabolic syndrome (p = 0.29).

Conclusions

The extent of MSU burden does not increase the estimated risk of cardiovascular events in gout patients.

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.

Acute Gouty Knee Arthritis: Ultrasound Findings Compared With Dual-Energy CT Findings

OBJECTIVE

The purpose of this study was to compare findings of ultrasound (US) with dual-energy CT (DECT) findings in patients presenting with suspected gouty knee arthritis.

SUBJECTS AND METHODS

This prospective study included 65 patients (52 men and 13 women; median age, 61.7 years [range, 38-87 years]) with an initial clinical diagnosis of acute gouty knee arthritis who underwent DECT performed using a 128-MDCT scanner and US performed using a 5-18-MHz transducer. Both intra- and extraarticular findings obtained using each modality were tabulated.

RESULTS

DECT identified gout as the final diagnosis for 52 of 65 patients (80.0%). An alternative diagnosis was confirmed for the remaining 13 patients. US detected gout in 31 of 52 patients (sensitivity, 59.6%) and produced findings negative for gout in seven of 13 patients (specificity, 53.8%). The double contour sign on US was positive for gout in 23 of 52 patients (44.2%) and negative in 12 of 13 patients (92.3%). Extraarticular urate deposition was identified by DECT in 44 of 52 patients, compared with identification by US in 11 of 52 patients (p < 0.001).

CONCLUSION

The sensitivity of US for the diagnosis of gouty knee arthritis is limited, particularly with respect to extraarticular urate deposition. The double contour sign is the single most valuable sign for the assessment of gouty knee arthritis by US.

Assessment of cardiovascular risk profile based on measurement of tophus volume in patients with gout

Hyperuricemia and gout are associated with increased risk of cardiovascular disease and metabolic syndrome. The aim of this study was to evaluate the correlation of total tophus volumes, measured using dual-energy computed tomography, with cardiovascular risk and the presence of metabolic syndrome. Dual-energy computed tomography datasets from 91 patients with a diagnosis of gout were analyzed retrospectively. Patients who received urate lowering therapy were excluded to avoid the effect on tophus volume. The total volumes of tophaceous deposition were quantified using automated volume assessment software. The 10-year cardiovascular risk using the Framingham Risk Score and metabolic syndrome based on the Third Adult Treatment Panel criteria were estimated. Fifty-five and 36 patients with positive and negative dual-energy computed tomography results, respectively, were assessed. Patients with positive dual-energy computed tomography results showed significantly higher systolic blood pressure, diastolic blood pressure, fasting glucose, and higher prevalence of chronic kidney disease, compared with those with negative dual-energy computed tomography results. The total tophus volumes were significantly correlated with the Framingham Risk Score, and the number of metabolic syndrome components (r = 0.22 and p = 0.036 and r = 0.373 and p < 0.001, respectively). The total tophus volume was one of the independent prognostic factors for the Framingham Risk Score in a multivariate analysis. This study showed the correlation of total tophus volumes with cardiovascular risk and metabolic syndrome-related comorbidities. A high urate burden could affect unfavorable cardiovascular profiles.