Though there are some medical tests that can detect common viral agents like rhinovirus, they are rarely used since the common cold tends to abate before a true medical test is necessary. To properly diagnose a cold that is severe or persistent, your physician may start with a physical examination that is likely to include checking your lungs, sinuses, throat and ears, and will ask questions about your symptoms, including how long they have lasted. Your doctor may also take a throat culture or order a blood test in order to rule out other potential causes of your symptoms. He or she will then recommend treatment options.