Significance of calcium pyrophosphate dihydrate and monosodium urate crystal identification in synovial fluid of arthritic patients

ABSTRACT

Diagnosis of joint arthritis usually depends upon certain clinico-investigatory criteria settled by international organizations. These criteria do not reveal a solid diagnosis in many occasions, also sometimes coexistence of more than one type of arthritis results in poor management and worsen the prognosis of the case. This descriptive study aimed to evaluate the role of synovial fluid crystal identification in reaching a final diagnosis of undiagnosed effusion - associated arthritis, also, to assess the value of crystal identification in diagnosis of coexistence of two or more types of arthropathies. Sixty-one patients with established joint effusion due to arthritis [acute or chronic] were included in the study. The patients were grouped into six groups according to the type of rheumatological disease after careful clinical, laboratory and radiological evaluation. Twelve cases were diagnosed as rheumatoid arthritis [RA], sixteen as osteoarthritis [OA], nine as gout, one as pseudogout, four as systemic lupus erythematosus [SLE], and four as spondyloarthropathies [SPA]. The seventh group was the undiagnosed group. All patients had subjected to synovial fluid [SF] aspiration by arthrocentesis. The aspirated samples were examined macroscopically, and microscopically for leucocytic count and crystals using polarized light microscopy [PLM]. Two types of crystals were specifically looked for monosodium uratre [MSU] crystals that cause gout and calcium pyrophosphate dihydrate [CPPD] crystals that cause calcium pyrophosphate deposition disease. Other laboratory investigations included C- reactive protein, serum uric acid, and rheumatoid factor. After using [PLM] we found that, out of 61 cases examined, twenty samples [32.8%] showed crystals[six[9.8%] were MSU, nine[14.8%] CPPD, and five[8.2%] showed both MSU and CPPD crystals], Examination of SF for MSU and CPPD crystals showed significant changes in the diagnosis of arthritis. Out of 61 examined cases, combined arthritis was diagnosed in ten cases [16.4%] [combined OA and CPPD in five cases, combined RA and CPPD in two cases, and combined RA, MSU and CPPD in one case, combined SLE and CPPD was diagnosed in one case and combined SPA and MSU in another one]. Consequently, PLM examination allowed us to reduce the undiagnosed cases from 24.6% to 16.4%. In conclusion: Examination of SF for MSU and CPPD crystals is worth looking and can change the management strategy. It allowed us to reach a definite diagnosis in undiagnosed arthritis,and to identify the coexistence of two or more types of arthropathies. Polarized light microscopy remains the only practical way for identifying SF crystals