Bridging the Diagnostic Gap in Calcium Pyrophosphate Deposition Disease and Basic Calcium Phosphate Arthropathies: Translating Research Advances into Routine Clinical Care

Basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPPD) crystals drive the degenerative and inflammatory pathways that lead to crystal arthropathy. Although recent classification criteria and imaging recommendations have improved standardisation for CPPD disease, it remains underdiagnosed in practice. In contrast, BCP disease lacks validated classification criteria and standardised diagnostic descriptors, limiting translational research and clinical recognition. Accurate diagnoses are limited by varied reference standards, operator-dependent techniques, and the absence of validated bedside tools. As the population ages and the burden of crystal disease rises, there will be increased demand for reliable diagnostic tools in clinical practice. This review summarises current and emerging diagnostic tools for identifying BCP and CPPD, with emphasis on bridging the diagnostic gap from research to routine care. Polarised light microscopy remains a highly specific test for the diagnosis of CPPD but is limited by inter-observer variability and access to polarising light microscopes. Imaging tools such as ultrasound, conventional radiography, computed tomography (CT) and dual-energy CT can identify CPPD, although performance varies by anatomical site, disease stage and technical parameters. Ultrasound is a useful bedside tool for identifying BCP disease, whereas CT and DECT also have diagnostic utility but lack validation for routine use. Emerging technologies such as computational polarised light microscopy and Raman spectroscopy are promising techniques, but require further research to evidence their use in clinical practice. Development of clear diagnostic reference standards, classification criteria for BCP disease, and evidence-based multimodal diagnostic pathways are essential to bridge the gap between research and routine clinical diagnosis.