We too have a DxH600 it took a while but we did validate the instrument for body fluids. The higher counts correlated better than the low counts. Is there someone you can get samples from close by? We basically manually count all clear samples as they do not correlate. Our linearity is for body fluids is 10-66,000 for WBC and 150-5M for RBCs so CSF really cannot be done on the instrument unless it is cloudy.