For someone who is exhibiting symptoms but has not been diagnosed, no single test is considered sufficient in diagnosing rabies in a living person, but the following tests may be done in some situations.
In some cases, providers check the person’s spinal fluid. This involves the use of a lumbar puncture, also known as a spinal tap. With the help of a special needle, healthcare providers can extract a small amount of cerebrospinal fluid (CSF) from the spinal canal then send that sample to a laboratory for analysis.
Although they’re often done in hospitals, lumbar punctures are sometimes performed right at the healthcare provider’s office. The total procedure takes about 15 minutes.
After using a local anesthetic to numb your skin, your healthcare provider will insert a thin needle into the lower part of your lumbar spine. In order to make enough room for the needle, you may be asked to bend forward, usually while sitting down or lying sideways.
Once your spinal tap is completed, you should lie down for at least an hour and spend the next 24 hours resting and drinking plenty of fluids. In many cases, patients will need to stay at the hospital or healthcare provider’s office for up to four hours.
While people rarely experience serious complications after undergoing a spinal tap, you may feel some pain when the needle is inserted. In the hours (or sometimes days) following the procedure, some patients also experience headaches, nausea, rapid heart rate, and/or low blood pressure.
If you experience bleeding or signs of inflammation after a spinal tap, consult your healthcare provider right away.
Skin biopsies are another type of lab test sometimes used to diagnose rabies. After numbing the area with a local anesthetic, your healthcare provider will take a small sample of the skin at the nape of your neck. In the lab, analysts will check the sample for rabies virus proteins.
Healthcare providers may look for antibodies to the rabies virus in samples of your saliva and serum (i.e., the liquid portion of blood that remains after coagulation). The presence of antibodies indicates an infection.