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Materials and Methods
We chose 18 and 42 samples sent for synovial and ascitic fluid analysis, respectively. The fluid samples were sent to the laboratory in Vacuette K3 ethylenediaminetetraacetic acid 3-mL tubes (Greiner Bio-One, Frichenhausen, Germany). All tests were analyzed within 4 hours of sampling. Manual counts were done using a Bright-Line hemocytometer (Sigma-Aldrich, St Louis, MO). Automated analysis was done twice on an Advia 2120, once using the regular channel and once using the channel that checks only for TNCs. For the TNC, the basophil/lobularity and peroxidase channel cytograms are modified specifically for the light scatter characteristics of the cells in body fluid samples. The WBC count from the peroxidase channel (WBCP) is compared with the TNC count from the basophil/lobularity channel. When the TNC does not agree with the WBCP count within limits specific to the body fluid application, the TNC count is flagged with an asterisk. The synovial fluid tests were done once with and once without the addition of 1 mg of hyaluronidase (from bovine testes type VIII, 683.6 units/mg, lyophilized powder, Sigma-Aldrich) to a final concentration of more than 250 U/mL. The samples were inverted 10 times and not incubated. The proportion of neutrophils on the Advia 2120 was compared with counts obtained on fluid smear review (prepared after centrifugation at 1,500g for 5 minutes, smeared and stained with Wright-Giemsa). Fluid smears for ascitic fluid were reviewed only if the total WBC count was more than 250 cells/μL, the upper limit of the reference interval for polymorphonuclear cells. Concordance was examined using a predetermined cutoff value of 1,999 cells/μL for synovial fluid, and 249 cells/μL for ascitic fluid. Median values with 25% to 75% ranges were compared because the test results were not normally distributed. The Pearson coefficient was used to test for correlations if the relationships were linear, and had high correlations on the Spearman rank test.
The data for this study are part of our quality management system. Use of the data is in accordance with the ethical standards established by Clalit Health Services.
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