[Alizarin red staining of articular fluids. Comparison of the results with electron microscopy and clinical data]

Coloration of articular fluids with alizarin S red has been proposed as a method of sensitive detection of calcium microcrystals, especially apatite crystals. We are reporting the results of a study of 230 non-selected fluids. The results of the coloration were quantified into negative, slightly positive, moderately positive and strongly positive. Study of X-Rays of the tapped joint and of the hospital file was done in 199 patients. Electron microscope study, of 44 fluid samples, shows that the coloration with alizarin red permits a reliable detection of calcium microcrystals in the articular fluid, only if the strongly positive results are taken into account. But the coloration is not specific for apatite: 5 strongly positive fluids out of 14 contain only, in electron microscopy, crystals of dihydrated calcium pyrophosphate. 10.8% of the stained fluids give a strongly positive result. In two cases, it concerns destructive arthropathies of the shoulder with periarticular calcifications. The other strongly positive results are found in chondrocalcinosis (52 p. cent), in arthrosis (17 p. cent) and in rheumatoid polyarthritis (15 p. cent). As a whole, the results are correlated with age and the degree of radiological destruction. The similar percentage of strongly positive fluids observed in arthrosis and rheumatoid polyarthritis, is not in favor of a specific role of apatite microcrystals in the pathogenesis of arthrosis. Since the majority of strongly positive fluids come from joints which are very destroyed, regardless of the arthropathy concerned (rheumatoid polyarthritis, chondrocalcinosis or arthrosis), it is possible to think that it is mostly the destruction of the sub-chondral bone which explains these results.