Abstract: Objective To investigate the effect of small red blood cells on the determination of platelets by using Sysmex XT4000-i automatic blood cell analyzer, manual detection and automatic blood cell analyzer Sysmex XT-4000i were used to measure each blood sample. Methods 210 blood samples were collected from patients treated in our hospital from October 2015 to September 2017. According to the average volume of red blood cells （MCV）, patients were divided into A, B, C three groups, the C group of patients in accordance with the distribution of red blood cells in the normal range is divided into two groups were studied.The platelets in each blood sample were measured by manual detection and instrumentation. Results The platelet count of blood samples in group A and group B was significantly higher than that in manual test （P<0.05）. There was no significant difference in blood samples between group A and group B （P>0.05）. There was no significant difference in the platelet count between the two Methods （P>0.05）. There was no significant difference between the two Methods in the RDW group （P>0.05）. Conclusions mall red blood cells can affect the platelet count detected by automatic blood cell analyzer Sysmex XT-4000i.

Key words: Platelet, Small red blood cells, Automatic blood cell analyzer