P004 Rheumatologist vs pathology department: correlation of crystal identification in synovial fluid analysis

Background/Aims Crystal arthritis is the commonest inflammatory arthritis in adults. Diagnosis relies mostly on the correct identification of crystals under red-compensated polarized microscopy with assessment of birefringence. This is done routinely in our department when opportunity arises. Failure to appropriately identify crystals may result in lengthy hospitalisations, complications, avoidable repeated urgent visits, and unnecessary cost. We aimed to examine the agreement between rheumatology vs pathology-based microscopy for crystal analysis. There is currently no standardized pathway for synovial fluid crystal analysis in our tertiary centre in Dublin. Methods A prospective study at Mater Misericordiae University Hospital - Dublin, was started in Dec 2019. Synovial fluid samples were obtained from acutely inflamed joints where clinically indicated. Fresh samples which were found to contain crystals (MSU or CPP) by a rheumatology consultant or trained registrar using compensated polarized microscopy, were also simultaneously sent to our pathology laboratory to receive similar analysis. Ethical approval was granted and all patients consented for their joint fluid to receive double analysis. Results 33 samples have been analysed to date. 13 samples of MSU crystals and 20 CPP crystals (table 1). Both rheumatologist and pathologist agreed on all but only one MSU sample. The pathologist identified CPP crystals only on 2/20 samples. The fluid analysis was carried out within the same working day by rheumatologist Vs. median of 2.3 working days for the result by the pathologist. Conclusion The study showed a high agreement between rheumatologists and pathologists on identification of MSU crystals (92%), but very poor agreement on CPP crystals (only 10%). A quality improvement project is currently underway to address this issue and bridge the gap. Majority of Rheumatologists don't routinely perform crystal analysis using polarized microscopy and rely on their local cellular pathology lab for the results. Rheumatologists need to liaise with their local pathologists to optimise and streamline the process of crystal microscopy specially CPP crystals. P004 Table 1:crystals samples analysed through rheumatology and pathologyCPPD positiveMSU positiveRheumatologist2013Pathologist212Total2013 Disclosure A. Abdalla: None.