title: Relationship between automated total nucleated cell count and enumeration of cells on direct smears of canine synovial fluid.
abstract: Canine osteoarthritis is a common disorder seen in veterinary clinical practice and causes considerable morbidity in dogs as they age. Synovial fluid analysis is an important tool for diagnosis and treatment of canine joint disease and obtaining a total nucleated cell count (TNCC) is particularly important. However, the low sample volumes obtained during arthrocentesis are often insufficient for performing an automated TNCC, thereby limiting diagnostic interpretation. The aim of the present study was to investigate whether estimation of TNCC in canine synovial fluid could be achieved by performing manual cell counts on direct smears of fluid. Fifty-eight synovial fluid samples, taken by arthrocentesis from 48 dogs, were included in the study. Direct smears of synovial fluid were prepared, and hyaluronidase added before cell counts were obtained using a commercial laser-based instrument. A protocol was established to count nucleated cells in a specific region of the smear, using a serpentine counting pattern; the mean number of nucleated cells per 400 × field was then calculated. There was a positive correlation between the automated TNCC and mean manual cell count, with more variability at higher TNCC. Regression analysis was performed to estimate TNCC from manual counts. By this method, 78% of the samples were correctly predicted to fall into one of three categories (within the reference interval, mildly to moderately increased, or markedly increased) relative to the automated TNCC. Intra-observer and inter-observer agreement was good to excellent. The results of the study suggest that interpretation of canine synovial fluid samples of low volume can be aided by methodical manual counting of cells on direct smears.
authors.affiliation: Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA.
authors.forename: Allison
authors.initials: A
authors.lastname: Dusick
authors.affiliation: Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Young
authors.affiliation: Comparative Orthopaedic Research Laboratory and Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA. Electronic address: muirp@vetmed.wisc.edu.
authors.forename: Peter
authors.initials: P
authors.lastname: Muir
mesh_terms: D000818:Animals; D002452:Cell Count / Q000295:instrumentation / Q000592:standards / Q000662:veterinary*; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D005260:Female; D007834:Lasers; D008297:Male; D010003:Osteoarthritis / Q000175:diagnosis / Q000662:veterinary*; D011446:Prospective Studies; D012044:Regression Analysis; D013582:Synovial Fluid / Q000166:cytology*; D014922:Wisconsin
keywords: Automated cell counts; Dog; Joint fluid; Manual cell counts; Total nucleated cell counts