Blood analyzing method and blood analyzer

A blood analyzer, comprising:

• a sample preparing apparatus configured to mix a fluorescent dye and a blood sample to prepare a measurement sample without lysing red blood cells to produce a difference in fluorescence intensity between mature red blood cells and reticulocytes in the measurement sample;
• a detecting apparatus comprising a light source and a plurality of photodetectors, wherein the plurality of photodetectors respectively detect scattered light and fluorescent light produced from the measurement sample after being irradiated with light from the light source on the unlysed blood cells in the measurement sample, wherein the plurality of photodetectors respectively outputting fluorescence data related to the fluorescent light and scattered light data related to the scattered light for each unlysed blood cell in the measurement sample;
• and
• a hardware controller comprising a processor which executes a program stored in—a non-transitory memory—to:
• output scattergram data to display a plot, wherein the plot having an intensity of the fluorescence data related to the fluorescent light on one axis and an intensity of the scattered light data related to the scattered light on another axis, wherein a range of the intensity of the detected fluorescence data is partitioned into a mature red blood cell distribution range and a reticulocyte distribution range, wherein the reticulocyte distribution range is further partitioned into a low fluorescence intensity range, a mid fluorescence intensity range and a high fluorescence intensity range;
• obtain from the scattergram data, a proportion of the unlysed blood cells included in the low fluorescence intensity range in the reticulocyte distribution range;
• obtain a first value reflecting a first centroid position based on the scattered light data in the reticulocyte distribution range;
• obtain a second value reflecting a second centroid position based on the scattered light data in the mature red blood cell distribution range;
• and
• determine the presence of plasmodium falciparum parasites in the unlysed blood sample based on the proportion of the unlysed blood cells included in the low fluorescence intensity range in the reticulocyte distribution range and a difference between the first value reflecting the first centroid position and the second value reflecting the second centroid position.