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.

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BackgroundIn Giant Cell Arteritis (GCA) two dominant cytokine clusters have been linked to disease activity, IL-6 – IL-17 axis (Th17) and IL-12 – IFN γ axis (Th1). The first one related to systemic symptoms and the second route responsible for ischemic symptoms. Tocilizumab (TCZ) performs its effect mainly by inhibiting Th17 axis and terminally Th1 route.ObjectivesOur aim was to evaluate the effect of TCZ on ischemic and systemic symptoms throughout the follow-up.MethodsRetrospective, multicenter study of 134 patients diagnosed of GCA on treatment with TCZ. We evaluate the efficacy of TCZ by improving ischemic (visual involvement, headache, jaw claudication) and systemic symptoms (fever, constitutional syndrome, polymyalgia rheumatica (PMR)).ResultsWe evaluated 134 patients (101 w/33 m) and its main symptoms at TCZ onset, TABLE. 73 (54.5%) patients presented PMR followed by headache in 70 (52.2%) cases, constitutional syndrome in 31 (23.1%) and visual involvement in 28 (20.9%) patients. After one month of treatment there was an important clinical improvement, persisting in 13,6% of patients PMR, 10.6% headache and 10.6% visual involvement. Throughout the follow-up, the improvement of ischemic symptoms was slower. At month 12, in 5.6% (4) of patients persisted with visual impairment, and 2.8% (2) patients presented headache and constitutional syndrome. However, the analytical improvement was statistically significant from the first month and sustained during follow-up.ConclusionAccording to the results of our study, we can conclude that in clinical practice, ischemic symptoms take longer to improve than systemic symptoms; being visual affectation the most frequent symptom after 12 months of follow-up.References[1] Soriano A, Muratore F, Pipitone N, Boiardi L, Cimino L, Salvarani C. Visual loss and other cranial ischaemic complications in giant cell arteritis. Nat Rev Rheumatol. 2017; 13:476-84.[2] Ciccia F, Rizzo A, Ferrante A, Guggino G, Croci S, Cavazza A, et al. New insights into the pathogenesis of giant cell arteritis. Autoimmun Rev. 2017; 16:675-83.[3] Calderón-Goercke M. Tocilizumab in giant cell arteritis. Observational, open-label multicenter study of 134 patients in clinical practice. Semin Arthritis Rheum. 2019Jan5. pii: S0049-0172(18)30571-7. Doi: 10.1016/j.semarthrit.2019.01.003. [Epub ahead of print]Disclosure of InterestsMonica Calderón-Goercke: None declared, J. Loricera: None declared, D. Prieto-Peña: None declared, Vicente Aldasoro: None declared, Santos Castañeda Consultant for: Amgen, BMS, Pfizer, Lilly, MSD, Roche, Sanofi, UCB, Ignacio Villa-Blanco: None declared, Alicia Humbría: None declared, Clara Moriano: None declared, Susana Romero-Yuste: None declared, J. Narváez Consultant for: Bristol-Myers Squibb, Catalina Gomez-Arango: None declared, Eva Perez-Pampín: None declared, Rafael Melero: None declared, Elena Becerra-Fernández: None declared, Marcelino Revenga: None declared, Noelia Alvarez-Rivas: None declared, Carles Galisteo: None declared, Francisca Sivera: None declared, Alejandro Olive...

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