Abstract: Objective To evaluate the performance of the body fluid （BF）mode on Sysmex XT-4000i for counting blood cells in cerebrospinal fluid （CSF）. Methods One hundred and forty -two CSF specimens were collected from the inpatients in Shandong Provincial Hospital from June to December,2015. Blood cells of all the specimens were counted for method comparison between Sysmex XT-4000i and manual microscope （counting chamber and stained cytospin slides）.Results Excellent correlations were found for counting white blood cells （y=1.17x+3.21,n=118,r²=0.98）,mononuclear cells （y=0.81x+13.61,n=101,r²=0.88）,polynuclear cells （y=0.82x+5.15,n=101,r²=0.88）and red blood cells （y = 1.01x+146.40,n = 62,r²= 0.99）. Good agreement was found between levels of high fluorescent （HF）cells detected by XT-4000i and large cells （macrophages or malignant cells）found under the microscope （y = 0.54x+3.31,n= 101,r²= 0.27,P <0.000 1）. The true positive rate of HF cells was 13.9% and their true negative rate was 96.9%. However,no correlation was found between eosnophils detected by XT-4000i and under the microscope （P >0.05）. The true positive rate of eosnophils was 9.8% and their true negative rate was 80.0%. Good precision （CV≤30%）was got in white blood cells,mononuclear cells,polynuclear cells and red blood cells counted by XT-4000i. Both carry-over （≤0.3%）and linearity （r²=0.99）were also excellent for white blood cells and red blood cells. Conclusion The BF mode on XT-4000i may be routinely used for CSF cells count because of its excellent accuracy and precision. HF cells may have some predictive value in large cells in CSF.

Key words: Cerebrospinal fluid, Blood cell count, Hematology analyzer, Sysmex XT-4000i