To compare two technetium-99m scintigraphic techniques - 99mTc-labelled
antibodies against granulocyte non-specific cross-reacting antigen-95 and 99mTc-exametazime labelled leucocytes in
ulcerative colitis - 23 consecutive patients undergoing colonoscopy were investigated in a prospective and randomized study. In each patient the two scans and colonoscopy and biopsy were performed within 10 days. Scans, endoscopy and histology were independently graded for degree of
inflammation in eight different colorectal segments for each patient. Active
inflammation in one or more segments was present on endoscopy in 22 patients and on histology in 17 patients. Twenty-two patients had increased uptake on the antibody scan and 21 patients on the
exametazime scan. Twelve patients showed the same disease extent with both scan methods (total
colitis, n=10; distal
colitis, n=2). Compared with endoscopy, sensitivity for
inflammation in individual segments was 0.51 for antibody scan and 0.87 for
exametazime scan; specificity was 0.67 and 0.55, respectively. The predictive value for presence of
inflammation was 0.66 for antibody scan and 0.72 for
exametazime; the predictive value for absence of
inflammation was 0.52 and 0.77, respectively. Segmental scan uptake of endoscopically or histologically visualized
inflammation was consistently lower for antigranulocyte
antibodies than for
exametazime. It is concluded that in patients with active
ulcerative colitis,
inflammation is better visualized with 99mTc-exametazime labelled leucocytes than with 99mTc-labelled antigranulocyte
antibodies. The antibody technique offers the advantage of in vivo labelling, but is less reliable than the
exametazime method for imaging of colonic
inflammation.