POS0134 INCREASED PREVALENCE OF LUMBAR SPINE MONOSODIUM URATE DEPOSITION AMONG GOUT PATIENTS ON DUAL-ENERGY CT

Abstract

Background:Gout affecting the spine is reported as a rare event presenting with neuropathy, spinal compression and acute back pain (1). Cases are often diagnosed by tissue confirmation of monosodium urate (MSU) deposition. The frequency of gout involving the spine asymptomatically or with milder, non-specific symptoms is likely higher than reported.Objectives:Using dual-energy CT (DECT), we are determining prevalence/extent of MSU deposition in the lumbosacral spines of patients with gout and tophaceous gout, compared to non-gout controls.Methods:We are recruiting 25 controls, 25 non-tophaceous and 25 tophaceous gout patients, 45-80 years old. Exclusion criteria include CPPD disease, RA, spondyloarthropathy or spinal malignancy. All gout subjects meet ACR gout classification criteria with entry serum urate (sU) of >6.8 mg/dL, or sU >6.0 mg/dL on ULT for <6 months. Demographics, gout history, Aberdeen back pain scale, sU, ESR, and CRP are collected. DECT of the lumbosacral spine is used to assess MSU deposition and osteoarthritic changes.Results:63 subjects are enrolled and analyzed to date (25 control, 23 non-tophaceous and 15 tophaceous gout). Control, non-tophaceous gout, and tophaceous gout subjects have similar mean age in years (controls 61.8±3.8, non-tophaceous 64.0±6.2, tophaceous 63.5±9.2, p=0.45), but differ in BMI (controls 28.3±6.5 kg/m2, non-tophaceous 32.1±6.7 kg/m2, tophaceous 29.1±4.3 kg/m2, p=0.01) and creatinine (controls 1.0±0.2 mg/dL, non-tophaceous 1.4±0.6 mg/dL, tophaceous 1.7±0.9 mg/dL, p=0.048). Mean sU and ESR are higher in gout subjects (sU-controls 5.3±1 mg/dL, non-tophaceous 8.3±1.4 mg/dL, tophaceous 8.4±2.0 mg/dL, p<0.05; ESR-controls 13.7±13.8 mm/h, non-tophaceous 25.2±18.7 mm/h, tophaceous 22.5±15.1 mm/h, p<0.05). Using default threshold settings for MSU visualization, greater MSU deposition is observed in the spine of gout patients (controls 2.2±1.2 cm3, non-tophaceous 4.5±4.3 cm3, tophaceous 8.5±12.5 cm3, p<0.05; Table 1). Reanalysis of several scans using narrower threshold settings to limit possible artifact confirms increased MSU signal among gout patients. Although many subjects in each group do not have excessive MSU deposition, deposition is more common in both gout groups. No subject demonstrated a frank spinal tophus.Conclusion:Based on preliminary results, gout patients have higher inflammatory markers and greater spinal MSU deposition than controls. Preliminary analyes with more stringent DECT threshold settings suggests these differences are not artifact, but analysis is ongoing. These data suggest that MSU deposition in the spine occurs in a subset of gout patients.