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Introduction ⬇

A white blood cell (WBC) scan is an NMI test in which a sample of the patient’s own WBCs are isolated, labeled with indium oxine (111In), and reinjected. This scan is performed for localization of acute abscess formation and indicated for both adults and children with signs and symptoms of a septic process, fever of unknown origin, osteomyelitis, infected implanted devices, or suspected intra-abdominal abscess. The scan is also helpful in determining the cause of complications of surgery, injury, or inflammation of the GI tract and pelvis. Test results are based on the fact that any collection of labeled WBCs outside the liver, spleen, and functioning bone marrow indicates an abnormal area to which the cells localize. This procedure is 90% sensitive and 90% specific for acute inflammatory disease or acute abscess formation.

Procedure ⬆ ⬇

  1. Obtain a venous blood sample (lavender-topped tube) of 60 mL for the purpose of isolating and labeling the WBCs. The laboratory process takes about 2 hours to complete. The patient’s WBC count needs to be at least 4.0 so that there are enough cells to label for this procedure.

  2. Inject the labeled WBCs intravenously.

  3. Have the patient return for imaging after 24 or 48 hours.

  4. Imaging time is about 1 hour per session.

  5. See Chapter 1 guidelines for safe, effective, informed intratest care.

Clinical Implications ⬆ ⬇

Abnormal concentrations indicate:

  1. Acute abscess formation

  2. Acute osteomyelitis and infection of orthopedic prostheses

  3. Active inflammatory bowel disease

  4. Postsurgical abscess sites and wound infections

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain the purpose, procedure, benefits, and risks of NMI.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

  3. See standard NMI pretest precautions.

Posttest Patient Care

  1. Review test results; report and record findings. Modify the nursing care plan as needed. Counsel appropriately about need for further tests.

  2. Refer to standard NMI posttest precautions.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Clinical Alert

If the patient does not have an adequate number of WBCs, additional blood may have to be drawn. A gallium scan may be necessary if too few WBCs are present, or donor cells can be used

Interfering Factors ⬆ ⬇

  1. False-negative reactions are known to occur when the chemotactic function of the WBC has been altered, as in hemodialysis, hyperglycemia, hyperalimentation, steroid therapy, and long-term antibiotic therapy.

  2. Gallium scans up to 1 month before the test can interfere.

  3. False-positive scans occur in the presence of GI bleeding and in upper respiratory infections and pneumonitis when patients swallow purulent sputum.

Reference Values ⬆

Normal

Normal WBC (leukocyte) concentration and radiopharmaceutical distribution in the liver, spleen, and bone marrow

No signs of leukocyte localization outside of the reticuloendothelial system