$diffraction definition in crystals$

The reasons for this (other than the general low profile, in the past, of crystal arthritis) remain unclear, but as early as 1974 this lack of interest was noted. There is no other immediate procedure that allows such an unequivocal etiologic diagnosis in any other arthritic disease.ĭespite its immediacy and elegance, SF analysis is inconsistently implanted among rheumatologists, who as a community appear to have many that consider it dispensable. Using an adequately equipped microscope in the clinic allows an immediate and definitive diagnosis of crystal arthritis. SF analysis is a simple procedure requiring only a microscope fitted with polarized filters and a first-order red compensator the identification of MSU and CPPD crystals provides an unequivocal diagnosis of gout and CPPD crystal arthritis.

$diffraction definition in crystals$

Crystal identification in SF is included in the core curricula in rheumatology, by both the American College of Rheumatology and the European Board of Rheumatology, UEMS Section of Rheumatology. SF analysis for crystals has received little critical attention since its initial description, and the technique remains essentially unchanged. Hence, this review focuses on the search for MSU and CPPD crystals. The occasional finding of other, rarer crystals plays only an anecdotal role. BCP crystals are too small to be seen with an optical microscope as anything more, at the most, as crystal aggregates in amorphous clumps. The search for apatite and other basic calcium phosphate (BCP) crystals remains of less certain clinical relevance at this point, but this issue is addressed in Chapter 22. The identification of monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystals is clinically relevant when performing a synovial fluid (SF) analysis for crystals. MSU and CPPD crystals have characteristic angles of extinction of birefringence that can be seen when rotated between angles parallel and perpendicular to the axis of slow vibration of light of the first-order red plate compensator.

$diffraction definition in crystals$

The strong negative birefringence of MSU crystals and the weak positive birefringence of CPPD crystals, as well as differences in crystal shape under many, but not all, circumstances, helps distinguish MSU from CPPD crystals.Ī rotating microscope stage is helpful to distinguish MSU and CPPD crystals from birefringent debris in the joint fluid. However, this simple and rapid diagnostic approach is markedly underused in clinical practice. Synovial fluid crystal analysis performed with a compensated polarized light microscopy is the gold standard for identifying MSU and CPPD crystals and for distinguishing these pathologic crystals from a variety of other particles present in the synovial fluid. The identification of monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystals in synovial fluid or tissue biopsy samples is central to the definitive diagnosis of gout and CPPD deposition disease.īasic calcium phosphate crystals are too small to be viewed with an optical microscope other than as crystal aggregates that appear as amorphous clumps.

$diffraction definition in crystals$

Diffraction definition in crystals