The presence of calcium phosphate crystals such as basic calcium phosphate and calcium pyrophosphate dihydrate in intra-articular fluid is linked to a number of destructive arthropathies and detection of these deposits is often pivotal for early diagnosis and appropriate management of such disease.
We describe the use of a calcium-sensitive dye, Fluo-4, to selectively label calcium-containing mineral deposits in synovial fluid, which can then be easily visualized using a standard fluorescence microscope. Furthermore, we have combined the fluorescent properties of the tagged crystals with flow cytometry as a fast and semi-quantitative method of detection.
Dot-plots were used to quantify differences between various types of arthropathies and confirmed by visual observation of the crystals under a fluorescence microscope.