Complete Blood Count is a test to measure the concentration of different components in a blood like Heamoglobin,White Blood Cells,Red Blood Cell,Platelet count which determine anemia or other blood infections & ESR is a test which is conducted to check the speed at which the red blood cells precipitate over a period of time.The rate is an indication of inflammation and increases in many diseases.ESR is increased in rheumatoid diseases, most infections, and in cancer. An advanced rate doesn't diagnose a specific disease, but it does indicate that an underlying disease may be present. A physician can use ESR to monitor a person with an associated disease. When the disease worsens, the ESR increases; when the disease improves, the ESR decreases. The ESR doesn't always follow the course of cancer. ESR is called an acute-phase reactant test, meaning that it reacts to acute conditions in the body, such as infection or trauma. The rate increase follows a rise in temperature and white blood cells count, peaks after several days, and usually lasts longer than the elevated temperature or white blood cells count.