Osteomyelitis

If a patient has symptoms and signs that may indicate a bone infection, doctors may order the following tests or procedures to diagnose osteomyelitis: 

Blood tests

• Complete blood count (CBC) - To determine if there is an infection in the body, a doctor may draw blood for a complete blood count. An elevated number of white blood cells will show that an infection is present. (White blood cells attack and destroy organisms that are causing infection.)
• C-reactive protein (CRP) - To determine how much inflammation is present in the body, doctors may draw blood to run a CRP test, which measures the level of plasma protein (C-reactive protein) made by liver cells. A higher level may indicate infection or inflammation in the body.
• Erythrocyte sedimentation rate (ESR) - Drawing blood for an ESR allows doctors to measure the rate at which red blood cells settle at the bottom of a test tube filled with the patient’s blood sample. If the red blood cells settle at an increased rate, there may be inflammation in the body. This can help determine if an infection may be present. 

Imaging tests

• Computerized tomography (CT) - A CT scan combines several different X-ray images taken from various angles in order to provide cross-sectional views of the body’s structures. This allows doctors to see different bones, muscles, organs, and blood vessels in detail. In CT scans, however, bones sometimes obscure the images of organs and soft tissue.
• Magnetic resonance imaging (MRI) - This diagnostic test utilizes large magnets, radiofrequency, and a computer to create detailed images of organs and structures within the body. This can provide information on soft tissue and joint complications, as well as bone marrow swelling. MRIs can be especially useful for detecting the initial stages of osteomyelitis — even as early as one to two days after the onset of infection.
• Radioisotopic bone scan - This diagnostic procedure uses nuclear imaging to monitor various types of bone disease, including infections. Radioisotopic scans use tiny amounts of radioactive materials to create images of structures and functions within the body, showing blood flow to the bone, cell activity within it, and joint complications. As with MRIs, this procedure can detect osteomyelitis in its early stages.
• X-ray - Also known as plain films, this test uses invisible electromagnetic energy beams (X-rays) to create images of the bones. This can provide a general assessment of bone anatomy and help detect bone damage. However, X-rays may not show damage until osteomyelitis has been present in the body for several weeks.

Biopsy

Bone biopsies are often used to diagnose osteomyelitis. More specifically, a biopsy can determine what kind of bacteria or fungi has caused the infection. Open biopsies necessitate anesthesia and surgery. In some cases, a surgeon can instead insert a long needle through the skin and into the bone. This requires local anesthetic.