If your doctor suspects that you may have or have had in the past chickenpox or shingles he may have you do this lab. It is also used to check to see if you have an immunity or a chance of reactivating the VZV (Varicella Zoster Virus) infection before administering immunosuppressive drugs. This lab is used to distinguish whether the person has the virus. If a child, pregnant woman, or immune-compromised person comes in contact with someone who has chicken-pox, they should be tested.