Chronic monocytic arthritis

Synovial fluid cell analysis

Arthrocentesis has to be considered as a part of the clinical examination. A reasonable amount of aspirated synovial fluid is the best argument in favour of an objective articular disorder. Moreover some very simple evaluations are very helpful to make a diagnosis and to distinguish some particularities of rheumatic diseases. Such evaluations have to include both bacterial and synovial fluid analysis. Moreover, when performing synovial fluid analysis, a search for microcrystals is also performed. Haemarthrosis can easily be distinguished from a traumatic tap if the investigator is observing carefully the synovial fluid entering in the syringe. The diseases responsible for haemarthrosis differ with the age of patients: chondrocalcinosis, together with osteoarthrosis, is the most frequent aetiology in the elderly; disorders of haemostasis and synovial tumours are mostly observed in children and young adults. Paucicellular (< 1000 cells/mm3) synovial fluid is observed in different 'mechanical' disorders. In the case of purulent synovial fluid the primary diagnosis is septic arthritis. However, the most common aetiology is probably crystal-induced acute arthritis. Differential cell count analysis performed in case of 'inflammatory' (> 1000 or 2000 cells/mm3) synovial fluid usually shows a predominance of polymorphonuclear cells. However, high cellularity may sometimes be associated with a predominance of other cells, i.e. lymphocytes, monocytes, eosinophils. In this situation, such a simple evaluation (differential cell count analysis) is very helpful in making a diagnosis, e.g. eosinophilic arthritis, or to distinguish some particularities of rheumatic diseases, e.g. absence of cartilage breakdown in case of lymphocytic arthritis.

Cytologic examination of synovial fluid

Cytologic study of synovial fluid has been relatively neglected both by cytologists and rheumatologists. Currently identified implications of cytologic findings include definitive diagnoses of a variety of joint diseases such as those due to malignancies, infections, or pathogenic crystals. Diagnoses can also be strongly suggested, for example, by visualization of lupus erythematosus cells formed in vivo. Immunocytochemistry is being explored for diagnostic and pathogenetic implications. We propose that complementary techniques used in our cytology and rheumatology laboratories may provide new insights into the clinical significance of cellular changes in joint fluids.