Advances in the management of gout and hyperuricaemia

Recent developments in advanced imaging in gout

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

Ultrasound scans and dual energy CT identify tendons as preferred anatomical location of MSU crystal depositions in gouty joints

OBJECTIVE

The present study was performed to localize the articular deposition of monosodium urate (MSU) crystal in joints. We compare the detection efficiencies of dual-energy CT (DECT) and ultrasound scans.

METHODS

Analyses by DECT and ultrasound were performed with 184 bilateral joints of the lower limbs of 54 consecutive gout patients. All joints were categorized into (1) knee, (2) ankle, (3) MTP1, and (4) MTP2, and sorted into those with and those without detectable MSU deposition. The comparison of the positive rate between DECT and ultrasound and the agreement was performed using the McNemar test and the Cohen's κ coefficient, respectively. Next, we listed the MSU crystal deposition as assessed by ultrasound between the DECT-positive and -negative joints according to their interior structure. We included tendons, synovia, cartilage, subcutaneous tissue, etc. RESULTS: Among all joints, the percentages with MSU crystal deposition detected by DECT (99/184, 53.8%) and ultrasound (106/184, 57.6%) were comparable (P = 0.530 > 0.05). For MTP1 (21/34, 61.8%; 12/34, 35.3%; P < 0.05) and MTP2-5 (17/34, 50.0%; 10/34, 29.4%, P < 0.05), ultrasound and DECT were more efficient, respectively. The data concordance in 46 of 50 joints (92.00%; κ = 0.769, P < 0.05) for knee; and 27 of 34 joints (79.41%; κ = 0.588, P < 0.05) for MTP2-5 and suggested that tendons were the most frequent anatomical location of MSU crystal deposition.

CONCLUSIONS

The tendons are the most frequent anatomical location of MSU crystal depositions. The concordance rate of knee joints and MTP2-5 joints shows good agreement between DECT and ultrasound depending on the location.

Dual energy computed tomography: a novel technique for diagnosis of gout

AIM

To evaluate the sensitivity and specificity of dual energy computed tomography (DECT) for diagnosing gout compared with a composite gold standard (CGS) comprising joint aspiration and/or American College of Rheumatology clinico-radiographic criteria.

METHODS

Ninety patients of suspected gout underwent radiography and DECT of bilateral feet and knees. Radiographs and non-contrast CT (NCCT) were assessed for morphological characteristics, following which DECT was used to identify urate deposits.

RESULTS

With CGS as a reference (n = 90), sensitivity of radiographs was 15% (95% confidence interval [CI]: 6-27%) while specificity was 100% (95% CI: 90-100%). Sensitivity of NCCT was 26% (95% CI: 15-40%) while specificity was 97% (95% CI: 85-99%). Sensitivity of DECT was 82% (95% CI: 68-90%) while specificity was 89% (95% CI: 73-96%). Fifty-five patients underwent joint aspiration. Sensitivity and specificity of radiographs and NCCT with aspiration as a reference (n = 55) were not much different from that of CGS. However, DECT showed a higher sensitivity of 100% (95% CI: 86-100%) and a lower specificity of 48% (95%CI: 28-68%) with aspiration alone.

CONCLUSIONS

Dual energy computed tomography had higher sensitivity compared to conventional imaging with CGS as a reference; however, its specificity dropped with aspiration as a reference. It may be a useful adjunct for the diagnosis of gout, especially in the acute and inter-critical stage.

Detection of HLA-B*58:01 with TaqMan assay and its association with allopurinol-induced sCADR

BACKGROUND

The HLA-B*58:01 allele is associated with allopurinol-induced severe cutaneous adverse drug reactions (sCADR) in certain geographic regions, but the diversity of the correlation is large. In addition, the currently available HLA-B*58:01 testing methods are too laborious for use in routine clinical detection. The objective of this study was to develop a new, convenient method for the detection of HLA-B*58:01 and to investigate the association of HLA-B*58:01 with allopurinol-induced sCADR in a Han Chinese population.

METHODS

A new method combining sequence-specific primers (SSP) and TaqMan probe amplification was developed in this study and was used to detect the HLA-B*58:01 in 48 allopurinol-induced sCADR, 133 allopurinol-tolerant, and 280 healthy individuals. The accuracy, sensitivity, and specificity were assessed by a commercial PCR-SSP HLA-B typing kit. The low limit of detection was detected by serial dilution of an HLA-B*58:01-positive DNA template.

RESULTS

The new method successfully identified HLA-B*58:01 in thousands of HLA-B alleles, and the results for 344 DNA samples were perfectly concordant with the results of the commercial PCR-SSP HLA-B kit. The analytical sensitivity is 100% and the specificity is over 99%. The low limit of detection of this assay is 100 pg DNA, which was 10 times more sensitive than the commercial PCR-SSP kit. HLA-B*58:01 was present in 93.8% of the patients with sCADR, 7.5% of the allopurinol-tolerant patients, and 12.1% of the healthy controls. The frequency of HLA-B*58:01 was significantly higher in the sCADR group than in the control group (p<0.0001). However, there was no significant difference between the allopurinol-tolerant and control groups (p=0.1547).

CONCLUSIONS

HLA-B*58:01 has a strong association with allopurinol-induced sCADR in Han Chinese. The newly developed method is reliable for HLA-B*58:01 detection prior to allopurinol therapy.

Detection of structural waters and their role in structural dynamics of rhodopsin activation

Conserved structural waters trapped within GPCRs may form water networks indispensable for GPCR's signaling functions. Radiolysis-based hydroxyl radical footprinting (HRF) strategies coupled to mass spectrometry have been used to explore the structural waters within rhodopsin in multiple signaling states. These approaches, combined with (18)O labeling, can be used to identify the locations of structural waters in the transmembrane region and measure rates of water exchange with bulk solvent. Reorganizations of structural waters upon activation of signaling can be explicitly observed with this approach, and this provides a unique look at the structural modules driving the signaling process.

Dual-energy computed tomography compared with ultrasound in the diagnosis of gout

OBJECTIVES

The aim of our study was to compare dual-energy CT (DECT) with US for the diagnosis of gouty arthritis and to correlate the imaging findings with results from synovial fluid aspiration whenever possible.

METHODS

We recruited 21 patients (17 male and 4 female) who presented with a clinical suspicion of acute or chronic gout in 37 joints. DECT scans of the hands, wrists, feet, ankles, knees and elbows were performed. For post-processing, a colour-coding gout software protocol was used. US examinations of the same joints were performed. In addition, joint fluid aspiration was performed in a total of 14 joints.

RESULTS

DECT images were positive for urate crystal deposits in 25 of 37 joints. US findings were positive in 24 of 37 examined joints. In 12 of 14 joints the synovial fluid aspiration was positive. CT and US findings correlated in 32 of 37 joints (86.5%; κ = 0.698, P < 0.001). CT and synovial fluid results correlated in 12 of 14 joints (85.7%; κ = 0.417, P = 0.119). US and cytology findings correlated in 14 of 14 joints (100%; κ = 1, P < 0.001).

CONCLUSION

DECT and US have comparable sensitivity for the detection of gouty arthritis in a clinical setting. However, DECT results should be interpreted carefully, as there could be some false-negative findings.

Drug discovery for hyperuricemia

Hyperuricemia is associated with an increased risk of developing gout. This increases with the degree and duration of hyperuricemia. Gout can be managed by dietary modification and pharmacologic urate-lowering therapies. The recent identification of the renal apical urate/anion exchanger URAT1 (SLC22A12) and several membrane proteins relevant to the transport of urate play an important role in gaining a better understanding of the mode of action of many drugs used to treat gout. As described in this review, therapeutics designed to modify URAT1 transport activities might be useful in treating pathologies associated with hyperuricemia such as gout and urolithiasis. Continuing studies into the urate transportsome hold promise for the development of new, more effective therapeutics for hyperuricemia.

Dual-energy CT: a promising new technique for assessment of the musculoskeletal system

OBJECTIVE

Dual-energy CT (DECT) characterizes the chemical composition of material according to its differential x-ray attenuation at two different energy levels. Applications of DECT in musculoskeletal imaging include imaging of bone marrow edema, tendons, and ligaments and the use of monoenergetic techniques to minimize metal prosthesis beam-attenuating artifacts.

CONCLUSION

The most validated application of DECT is undoubtedly its noninvasive and highly specific ability for confirming the presence of monosodium urate deposits in the assessment of gout.

[Pharmacological management of inflammatory rheumatic conditions]

Inflammatory rheumatic disorders are related to different pathophysiological mechanisms and, hence, their therapeutic management varies according to the underlying disease. Crystal-induced arthritis is characterized by its almost specific responsiveness to colchicine. Regarding ankylosing spondylitis, non steroidal anti-inflammatory drugs (NSAIDs) and TNF blockers are the cornerstones of pharmacological intervention whereas oral corticosteroids at conventional doses are of little value, if any. Conversely, corticosteroids are the drug of choice to treat polymyalgia rheumatica. Furthermore, low-dose corticosteroids were shown to be more effective than NSAIDs in patients with rheumatoid arthritis (RA). However, the main goal being to achieve remission, disease-modifying antirheumatic drugs, either synthetic, especially methotrexate, and/or biologic, such as TNF inhibitors, have a major role in the management of RA. Finally, enhanced understanding of molecular pathogenesis of inflammatory disorders may help to find out how to best target available drugs to right individuals in the future.

Allopurinol to Febuxostat: How far have we come?

For decades allopurinol has been used as a xanthine oxidase inhibitor for treatment of hyperuricemia and gout. Although effective in many patients, some experience sensitivity to the drug. In some cases, this sensitivity may lead to allopurinol hypersensitivity disorder, which if untreated can be fatal. Recently the Food and Drug Administration has approved the use of febuxostat as an alternative therapy for hyperuricemia and gout. Febuxostat is a new xanthine oxidase inhibitor, but is not purine based and therefore decreases adverse reactions due to patient sensitivity. This review is a comprehensive look at the background of hyperuricemia and gout treatment with allopurinol compared to recent clinical studies with febuxostat. Each clinical study is evaluated and summarized, identifying the advances in treatment that have been made as well as the concerns that still exist with either treatment.

High-resolution melting analysis for the rapid detection of an intronic single nucleotide polymorphism in SLC22A12 in male patients with primary gout in China

OBJECTIVES

The human urate transporter 1 (URAT1, encoded by SLC22A12) was recently identified as the major absorptive urate transporter protein in the kidney responsible for regulating blood urate levels. The present study was designed to investigate the rs893006 polymorphism (GG, GT, and TT) in SLC22A12 in a total of 292 Chinese male subjects. Differences of clinical characteristics among the genotype groups were analysed.

METHODS

A total of 124 consecutive patients with diagnosis of primary gout and 168 healthy male volunteers were enrolled in this study. Demographic and clinical data were obtained from the patients and controls. DNA was purified from peripheral blood and the rs893006 polymorphism was determined with sequencing analysis. In addition, DNA samples were detected by high-resolution melting (HRM) analysis. Melting curves were analysed as fluorescence difference plots. The shift and curve shapes of melting profiles were used to distinguish the different genotypes.

RESULTS

GG, GT, and TT genotypes were unambiguously distinguished with HRM technology. Genotyping based on HRM analysis was fully concordant with the sequencing. Serum uric acid levels in the TT genotype subjects were significantly lower than those in the GG and GT genotypes. However, no differences among the groups were found in body mass index (BMI), blood pressure, creatinine, total cholesterol, and triglycerides. The TT genotype was observed more frequently among the low uric acid group than the high uric acid group.

CONCLUSIONS

HRM analysis is a simple, rapid and accurate one-tube assay for genotyping the SLCSSA12 gene. The rs893006 polymorphism in SLC22CA12 was confirmed to be a genetic risk for hyperuricaemia among the Chinese male population.

[Medical complications of lung transplantation]

In 2010, lung transplantation is a valuable therapeutic option for a number of patients suffering from of end-stage non-neoplastic pulmonary diseases. The patients frequently regain a very good quality of life, however, long-term survival is often hampered by the development of complications such as the bronchiolitis obliterans syndrome, metabolic and infectious complications. As the bronchiolitis obliterans syndrome is the first cause of death in the medium and long term, an intense immunosuppressive treatment is maintained for life in order to prevent or stabilize this complication. The immunosuppression on the other hand induces a number of potentially severe complications including metabolic complications, infections and malignancies. The most frequent metabolic complications are arterial hypertension, chronic renal insufficiency, diabetes, hyperlipidemia and osteoporosis. Bacterial, viral and fungal infections are the second cause of mortality. They are to be considered as medical emergencies and require urgent assessment and targeted therapy after microbiologic specimens have been obtained. They should not, under any circumstances, be treated empirically and it has also to be kept in mind that the lung transplant recipient may present several concomitant infections. The most frequent malignancies are skin cancers, the post-transplant lymphoproliferative disorders, Kaposi's sarcoma and some types of bronchogenic carcinomas, head/neck and digestive cancers. Lung transplantation is no longer an exceptional procedure; thus, the pulmonologist will be confronted with such patients and should be able to recognize the symptoms and signs of the principal non-surgical complications. The goal of this review is to give a general overview of the most frequently encountered complications. Their assessment and treatment, though, will most often require the input of other specialists and a multidisciplinary and transversal approach.

Effect of hypouricaemic and hyperuricaemic drugs on the renal urate efflux transporter, multidrug resistance protein 4

BACKGROUND AND PURPOSE

The xanthine oxidase inhibitors allopurinol and oxypurinol are used to treat hyperuricaemia, whereas loop and thiazide diuretics can cause iatrogenic hyperuricaemia. Some uricosuric drugs and salicylate have a bimodal action on urate renal excretion. The mechanisms of action of these hypo- and hyperuricaemic drugs on the handling of urate in renal tubules have not been fully elucidated. Recently, we identified the multidrug resistance protein (MRP) 4 as a luminal efflux transporter for urate in the proximal tubule.

EXPERIMENTAL APPROACH

Here, we studied the effect of these drugs on [(14)C]urate transport using human embryonic kidney 293 cells overexpressing human MRP4 and in membrane vesicles isolated from these cells.

KEY RESULTS

Allopurinol stimulated MRP4-mediated cellular urate efflux and allopurinol and oxypurinol both markedly stimulated urate transport by MRP4 in membrane vesicles. Bumetanide and torasemide had no effect, whereas furosemide, chlorothiazide, hydrochlorothiazide, salicylate, benzbromarone and sulfinpyrazone inhibited urate transport, at concentrations ranging from nanomolar up to millimolar. Probenecid stimulated urate transport at 0.1 microM and inhibited transport at higher concentrations.

CONCLUSIONS AND IMPLICATIONS

These data suggest that inhibition of MRP4-mediated urate efflux by furosemide and thiazide diuretics could have an important function in their hyperuricaemic mechanisms. Furthermore, stimulation of MRP4-mediated renal urate efflux could be a new mechanism in the hypouricaemic action of allopurinol and oxypurinol. In conclusion, MRP4 may provide a potential target for drugs affecting urate homoeostasis, which needs to be further evaluated in vivo.

Elderly-onset gout: a review

Elderly-onset gout (EOG), defined as a disease with onset at age 65 years or over, shows relevant epidemiological, clinical and therapeutic differences from the typical middle-age form. The main differences are the more frequent subacute/chronic polyarticular onset with hand involvement, the unusual localization of tophi on ostheoarthritis (OA) nodes, the increased female/male ratio and the frequent association with drugs that decrease renal urate excretion (diuretics and low-dose aspirin) and/or with primitive renal impairment. EOG has recently been confirmed as the most common inflammatory arthropathy in older people, with important demographic implications and substantial impact on daily clinical practice. Despite the high prevalence, gout, in the elderly, often remains misdiagnosed or diagnosed late in its clinical course. Even when correctly recognized, its treatment is often difficult or unsatisfactory.

Reduced Age-Related Cataracts Among Elderly Persons Who Reach Age 90 With Preserved Cognition: A Biomarker of Successful Aging?

Tissue damage due to oxidative stress has been implicated in aging, memory loss, and cataract formation. We hypothesized that persons who achieved exceptional longevity with preserved cognition (successful aging [SAG]) would exhibit a lower rate of age-related cataract (ARC) than the general population. The age-specific rates of ARC for a group of 100 (50 male, 50 female) elderly persons who reached at least age 90 years with preserved cognition were compared to the corresponding rates of ARC reported in five population-based studies. The principal finding of this report was that the SAG group manifested a significant reduction in the age-specific rate and lifetime cumulative incidence of ARC compared to the general population. Steroid use, alcohol consumption, gout, and skin lesions resulting from excessive sun exposure emerged as risk factors. Our findings suggest that the progressive development of lens opacities may be reflective of degenerative events occurring more generally throughout the body.

Increased serum uric acid--a marker of non-gouty widespread pain? A study of female patients with inflammatory and non-inflammatory pain

OBJECTIVE

To study the relationship between reported chronic pain and the level of serum urate (SU) among women with various diagnoses of the musculoskeletal system.

METHODS

Consecutive female patients (aged 20-70 years, n = 124), at rheumatology and rehabilitation practices, with chronic musculoskeletal pain of different origins were followed for 1 year after an initial survey of pain, lifestyle, quality of life, and disability. Repeated blood samples (including urate, creatinine, cholesterol, and glucose) were analysed. Multiple regression analysis was performed to explain initial variations in SU level in relation to pain and confounding factors.

RESULTS

The level of SU was increased among individuals with widespread pain (>5 locations) independent of underlying diagnoses compared to those with fewer pain sites (270.5 vs. 241.2 micromol/L). Serum creatinine, body mass index (BMI), the number of pain locations, and sleep disturbances independently contributed to the SU level and explained 43% of the variation in SU. Individual variation in SU during 4 months was low.

CONCLUSIONS

Epidemiological data on the relationship between the extent of body pain and SU were confirmed in a clinical setting. Besides known factors such as impaired renal function and obesity, widespread pain and sleep disturbances were related to an increase in SU. Medication and alcohol intake could not explain the findings. Longitudinal studies are necessary to elucidate whether the level of SU has any implications for the prognosis of chronic pain.