title: [Synovial fluid crystal identification by electron microscopy].
abstract: BACKGROUND
  In clinical practice crystal identification in synovial fluid is made by polarized light microscopy and with some specific stainings. Nevertheless, sometimes we are unable to identify crystals by these means, either because they are too small or because they are widespread on the fluid.
  
  
  OBJECTIVE
  To compare the identification of crystals in synovial fluid from patients with non-infectious monoarthritis but no history of local trauma or articular disease, using polarized light and electronic microscopy.
  
  
  METHODS
  We analized synovial fluid samples from patients with non-infectious monoarthritis and no history of local trauma or articular disease. First we used a polarized light microscope and alizarin red staining. Later we used conventional transmission electron microscopy and energy dispersive spectroscopy, in order to identify and characterize crystals.
  
  
  RESULTS
  Fourty-five samples from 23 synovial fluids were analyzed. Under polarized light microscopy we identified crystals on 11 samples: 3 with calcium pyrophosphate crystals, 6 with calcium basic phosphate crystals and 2 with sodium monourate crystals. On the remaining 12 samples we were unable to identify crystals. Samples were then analyzed by conventional transmission electron microscopy and energy dispersive spectroscopy confirming the presence of the previously identified crystals. On the remainig 12 samples we were able to identify calcium basic phosphate crystals.
  
  
  CONCLUSIONS
  Microcrystals seem to be an universal finding in synovial fluid of patients with osteoarthritis. The prevention of their deposition in joints might contribute to stop joint damage in this disease.
authors.affiliation: Serviço de Reumatologia, Hospital de Egas Moniz, Lisboa.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Nero
authors.forename: Isabel
authors.initials: I
authors.lastname: Nogueira
authors.forename: Rui
authors.initials: R
authors.lastname: Vilar
authors.forename: J Bravo
authors.initials: JB
authors.lastname: Pimentão
authors.forename: Jaime C
authors.initials: JC
authors.lastname: Branco
mesh_terms: D001168:Arthritis / Q000473:pathology*; D002118:Calcium / Q000032:analysis*; D002130:Calcium Phosphates / Q000032:analysis*; D002131:Calcium Pyrophosphate / Q000032:analysis*; D003430:Cross-Sectional Studies; D003460:Crystallization; D006801:Humans; D046529:Microscopy, Electron, Transmission; D012964:Sodium / Q000032:analysis*; D013582:Synovial Fluid / Q000737:chemistry*
chemical_list: D002130:Calcium Phosphates; C020243:calcium phosphate; D012964:Sodium; D002118:Calcium; D002131:Calcium Pyrophosphate