Cell Counts x 106/L
Done by a grid system per HPF
- x40
- averaged over 10 fields
Normal
- 0-200
Non Inflamm (Trauma / OA)
- 50 - 500
Inflamm (RA / Crystals)
- 1500 - 50 000
Infection
- > 50 000
- exception is gonococcal arthritis
Different Units
Standard now SI Units 10 x 106/ L
= 10 cells / mm3
= 10 x 103 /ml
= 10 x 103 /cc
= 10 x 105 /dl
= 10 x 105 /100ml
= 10 x 106 / L
Cell Differential
Polymorph %
- normal 0-25 %
- non inflammatory = 0- 25 %
- inflammatory = 30- 70 %
- infection > 75 %
Viscosity
- will decrease as inflamation increases
- effect of hyluronate lost
- hence sepsis = Low viscosity
Additional
Glucose < BSL
± Crystals as acid Ph decreases solubility
- presence of crystals does not exclude infection
Gram stain positive 30%
Culture positive 60%
Weinstein
WCC > 50,000 + > 90% PMN leukocytes
- should be considered infectious regardless of the culture results
Fink Clin Rheum Dis 1986;12:423.
- large series of culture-proven cases of bacterial septic arthritis
- only 44% had cell counts > 100,000 per mm3
- 34% of cases having counts of < 25,000 per mL