Experimental Factor Ontology identifier EFO_0007992 (basophil percentage of leukocytes) is a calculated measurement in which the number of basophil granulocytes is divided by the number of all white blood cells in a specified sample of peripheral venous blood, and the result presented as a ratio, fraction, quotient or percentage. A basophil is a granular leukocyte with an irregularly shaped, relatively pale-staining nucleus that is partially constricted into two lobes, and with cytoplasm containing coarse granules of variable size that stain bluish-black when exposed to basic dyes. Also known as: basophil count as percentage of total white blood cells, basophil count to total WBC count ratio, basophil percentage, basophil percentage of white cells, blood basophil count to total leukocyte count ratio.