There is a very slight exposure to radiation from the radioisotope. The spleen normally receives the highest dose of radiation because white blood cells normally accumulate in the spleen. The radiation from these materials is very slight, and the materials decompose (become no longer radioactive) in a very short time. Virtually all radioactivity is gone within 1 or 2 days. There are no documented cases of injury from exposure to radioisotopes. The scanner only detects radiation -- it does not emit any radiation.

However, because of the slight radiation exposure, most nuclear scans (including WBC scan) are not recommended for women who are pregnant or breastfeeding.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Extremely rarely, a person may experience an allergic reaction to the radioisotope. This may include anaphylaxis if the person is extremely sensitive to the substance.

The long delay before the person can be scanned may be undesirable for critically ill people.

Other tests (such as CT scan or ultrasound) may be required to confirm the presence of inflammation or infection indicated by an abnormal WBC scan.

False-negative results can theoretically occur as a consequence of antibiotic usage or chronic infection. Infection in the liver or spleen can be missed because of normal WBC accumulation in these organs.

False-positive results can occur from many causes, including (but not limited to) bleeding, the presence of tubes or catheters in the body, and skin wounds (such as surgical incisions). WBC accumulations in the lungs does not necessarily indicate an infection in the lungs.