What you really need to test in blood is the white blood cell count. You need to panic when your specific white blood cells called 'eosinophils' (large parasite hunters) range between 15 to 30 and beyond in the blood. Unless you are allergic that means that your body is fighting or at least keep you alive during parasitic infection because of them. Eosinophil are somewhat rare and the body won't release them unless you are dealing with something serious. Also roundworm family in general always make your body highly eosinophilic as they invade tissues be it lungs, organs or general muscle tissues. So the body respond by producing high amount of eosinophils. If you have a low amount of eosinophils you most likely dealing with something else.