Whether tests need to be done depends on how your child looks. If your child is eating and sleeping well and has periods of playfulness, and if his fever is low or can be well controlled, it is likely that he has only a mild illness. If, however, the fever is high or your child is behaving as if he is sick — sleeping a lot more or less than usual; refusing to eat or drink; acting especially moody; complaining of a headache, ear pain, a sore throat, belly pain, or diarrhea — there is likely an infection somewhere in the body. An infection is also likely if the fever persists for more than five to seven days. Although none of these symptoms individually indicates that the fever is a sign of something serious, together the constellation of symptoms may suggest a type of infection that needs to be identified and treated.
The type of test done really depends on what your doctor sees when examining your child. If his throat looks red and infected, your pediatrician will often take a throat culture to check for strep throat. If your child is complaining of pain with urination, or if the urine has a foul smell, a urine culture may be done to look for a urinary tract infection (UTI). If it is flu season and your child has flulike symptoms (severe muscle aches and vomiting), a test can be performed using mucus from the nose or throat to check for the presence of influenza. A child with tremendous congestion, a harsh cough, and breathing difficulty may be tested for respiratory syncytial virus (RSV) using a nasal wash. Sometimes these tests are available in doctors’ offices; other times they must be done at a laboratory or hospital.
If your child has a persistent fever (longer than five to seven days) and no source is apparent, or if your child appears to be very ill, blood tests will probably be done, including a complete blood count and a blood culture. Urine tests may be prescribed as well. For an extremely ill child, a spinal tap also will be performed, and the child will likely be hospitalized.
If coughing or vomiting is associated with the fever, an X ray may be done. The need for this depends on the history of the illness and what your doctor finds when she examines your child.