Comparison between Tc-HMPAO labelled white cells and Tc LeukoScan in the investigation of inflammatory bowel disease.

Objectives: (99m)Tc-HMPAO labelled leukocyte imaging (white cell scan) is used in the investigation and assessment of patients with inflammatory bowel disease (IBD), while (99m)Tc LeukoScan has been used to demonstrate the presence of orthopaedic infections and appendicitis. The single-injection technique used for the administration of LeukoScan removes the need for handling blood and the complex separation and labelling techniques that are required for white cell imaging. This study set out to investigate whether LeukoScan could be used to image IBD.

Methods: Twenty-two patients under investigation for suspected IBD agreed to undergo LeukoScan imaging within 7 days of their routine planar white cell scan. Following injection of 650 MBq (99m)Tc LeukoScan planar images were acquired at 1, 2 and 4 h and single photon emission computed tomography (SPECT) images at 4 h post-injection.

Results: When both sets of images were compared to the clinical diagnosis, the sensitivity and specificity were 0.88 and 0.83 for white cell imaging and 0.88 and 0.50 for LeukoScan SPECT at 4 h. The figures for the specificity and sensitivity of the LeukoScan 2 h and 4 h planar images were 0.44 and 1.00, and 0.75 and 0.50, respectively. When the LeukoScan and white cell images were compared, the 4 h LeukoScan SPECT images showed additional areas of uptake in 10 patients.

Conclusions: The study demonstrates that LeukoScan locates IBD. However, the sensitivity and specificity preclude its use for the routine detection of this disease. Comparisons with white cell scan images show that LeukoScan is taken up slowly in IBD and also appears in the normal bowel by 4 h.