Following the withdrawal of blood in a physician’s office or laboratory, patients may resume medications and food intake according to their physician’s orders. Immediately after the blood sample is taken, the test tubes are labeled with the date and the patient’s name, and they are sent to the laboratory for testing. Results are usually returned within 24 hours, depending on the tests performed. Based on the test results, additional blood tests may be ordered.

Test results are always evaluated in relation to the “normal range” for that test. The range of values considered to be normal is the range of test results from the blood of normal, active healthy people. When a person has arthritis or another disease or health problem, results may be higher or lower than normal – or “outside of the normal range.” When a physician sees that a blood test is outside of normal range, the tests may be repeated to verify results or additional tests may be ordered to determine the underlying causes behind the abnormality.

Normal ranges for some tests may vary slightly from lab to lab, especially between labs that use machines to perform blood tests and those in which blood tests are performed by hand. Frequently, results of a patient’s blood test are compared to another “known” blood sample taken from a healthy individual that is run at the same time and is designated as the “normal control.” When the “normal control” sample falls within the normal range, or reaches a specific “known” measurement, the laboratory results confirm that the blood test has been carried out accurately.

Although blood tests are very useful in the diagnosis of many conditions or diseases that cause chronic pain, other diagnostic tests are usually performed to determine the source of the pain and inflammation. These may include:

• Imaging tests. Tests that produce images of body parts, such as arthrography or other as x-rays, bone scan or other radionuclide imaging, CAT scan, MRI or ultrasound.

• Synovial fluid analysis. Test that analyzes fluid from an inflamed joint that is useful in diagnosing septic arthritis or juvenile rheumatoid arthritis.
  
  
• Electrodiagnostics. Tests that measure the electrical activity of nerves and muscles, such as electromyography or nerve conduction studies.
  
  
• Biopsy. Procedure in which a small sample of tissue is collected and examined under a microscope.
  
  
• Spinal tap (lumbar puncture). Insertion of a needle into the spinal canal to collect cerebrospinal fluid, to diagnose conditions including meningitis, encephalitis and some headaches. 

In addition to the blood tests, a urine test may also be used to diagnose certain inflammatory diseases, such as gout, one of the most painful forms of arthritis.