The AEC Test, or Absolute Eosinophil Count test, is a blood test that measures the number of eosinophils in the blood. Eosinophils are a type of white blood cell that plays a role in the immune system. The AEC Test is a simple and painless procedure. A blood sample is drawn from a vein in the arm and sent to a laboratory for analysis. The results of the test are usually available within a few days.