After the initial pain assessment, a number of diagnostic tests may be performed to help a physician identify the cause of pain when the results of a physical examination are inconclusive.

Common tests include blood tests and urine tests. Many other tests can be grouped into one of three categories:

• Radiologic evaluation. Use of devices that create images of the body using radiology. 
  
  
• Electrodiagnostic testing. Tests that measure the electrical activity of nerves and muscles.
  
  
• Quantitative sensory testing. Method used to assess damage to the small nerve endings that detect changes in temperature and the large nerve endings that detect vibration.

Radiologic imaging tests may include:

• X-ray. Low doses of electromagnetic radiation create an image of a body part, organ or bodily system on film or fluorescent screens. This is an inexpensive and widely available test that can detect fractures, bone damage and other conditions.
  
  
• MRI (magnetic resonance imaging).  Powerful magnets produce images on a computer screen and film. This test provides more detailed images than an x-ray and can detect damage to soft tissue. MRI may be used when more detailed information is necessary.

• CAT scan (computed axial tomography). Multiple x-rays are taken from different angles around the patient. As with an MRI, a contrast medium may be injected to highlight structures. This test provides more sophisticated images than an x-ray and can provide more detailed information about bone fractures, internal organs and other medical conditions.
  
  
• Arthrography. Injection of a contrast medium enhances an x-ray of a joint.
  
  
• Bone scans and other radionuclide imaging. These tests introduce tiny amounts of radioactive materials called tracers into the body. The tracer is either injected or swallowed. Once in the body, it travels through the bloodstream to the targeted area. The test is not painful, and can detect cancer, infection or other disorders.
  
  
• Myelography. This imaging test uses x-rays and fluoroscopy to provide pictures of the cavity within the bones of the spine (spinal column). This test may detect blockage of the spinal column caused by a tumor, infection, herniated disc or arthritis.
  
  
• Discography. An x-ray is taken after injection of a contrast agent into an intervertebral disc. The contrast agent enhances the definition of the tissue on the image and can detect damage of a disc.
  
  
• Arteriography. An x-ray is taken after injection of a contrast agent into the arteries. The test causes some discomfort but can detect blocked arteries.

Electrodiagnostic testing may include:

• Nerve conduction studies (NCS). These evaluate for damage to muscles or nerves. The test involves the use of a computer to monitor the muscle and nerve functioning. A small electrode is placed on the skin over the muscles or nerves being tested. Using a stimulator, a small electrical current is sent to the nerves being tested, which causes them to become active. Nerve activity is picked up the computer and analyzed by a physician. The electrical current produces only a small shock and does not damage the body.
  
  
• Repetitive nerve stimulation (RNS). This test evaluates muscle and nerve activity. It is conducted in a similar fashion to the nerve conduction study. The muscle or nerve being tested is stimulated numerous times to monitor activity.
  
  
• Needle electromyography. Needle electrodes are used to evaluate the electrical activity of muscle fibers. This test can identify muscle or nerve damage that may be causing pain.

Quantitative sensory testing (QST) may include:

• Mechanical nonpainful sensation. An instrument that measures nerve sensation evaluates individual nerve fibers. The instrument stimulates the nerve but does not cause pain. Nerve reactions are measured.
  
  
• Mechanical painful sensation. An instrument that causes pressure or a pinching sensation evaluates individual nerve fibers. This test involves creating a small amount of pain and measuring nerve reactions.
  
  
• Thermal sensation. This evaluates the response of individual nerve fibers to heat and cold.
  
  
• Current perception threshold (CPT). An instrument that emits a small vibration evaluates nerve fibers. Unlike the other tests that measure anatomical reactions to stimulus, CPT measures the patient’s perception of the stimulus.

The discomfort associated with electrodiagnostic and sensory testing varies among individuals. Some individuals experience more pain with the testing because of their condition prior to the testing. Other individuals experience little discomfort during the tests.

Other diagnostic tests include:

• Ultrasound. High-frequency sound waves painlessly highlight internal structures.
  
  
• Spinal tap (lumbar puncture). Analysis of cerebrospinal fluid drawn with a needle can help diagnose conditions such as meningitis and encephalitis.
  
  
• Biopsy. Analysis of a tissue sample can diagnose or rule out cancer.
  
  
• Interventional procedures. For example, facet joint (zygapophyseal) injection and selective nerve root injection are also sometimes used to make a diagnosis.

Patients’ abilities and limitations may also be further assessed in a functional capacity evaluation (FCE), offered in occupational therapy or physical therapy.

Pain is complex process that involves biological, psychological and social factors. For this reason, a psychological evaluation is often a part of assessment. This may include questions designed to assess a patient’s mood, pain-coping strategies, areas of disability and social environment. Some lifestyle aspects that a physician may ask about include:

• Work and finances
• Personal relationships
• Recreational pursuits
• Daily activities
• Sleep patterns
• Appetite
• Sex drive
• Ability to concentrate
• Energy level
• Presence of suicidal or other thoughts