A nasopharyngeal culture is a quick, painless test that is used to check the upper respiratory infection. It is done when you have symptoms such as a runny nose and cough. It is used to see what microorganism is causing the disease and it is done by letting them grow in a lab before analysing them. It can be any bacteria, fungi, or any virus can be used for upper respiratory disease and thus in the case of symptoms like chest congestion, chronic cough and runny nose the test is prescribed.