Estimated synovial fluid leukocyte numbers on wet drop preparations as a potential substitute for actual leukocyte counts.

Leukocyte counts on synovial fluid are widely used in classification of joint disease as inflammatory or "noninflammatory." We have evaluated estimates of leukocytes (WBC) per high power field (HPF) on wet drop preparations to see if they might be suitable substitutes in some situations. If there was a mean WBC of 0-2/field on 10 HPF, all leukocyte counts were less than 1,300/mm3. Thus, in such fluids expense might be reduced by eliminating the actual leukocyte count. Estimates also roughly correlated with WBC counts at higher counts but were less consistent.