Value of technetium-99m HMPAO-labelled leucocyte scintigraphy as an Initial screening test in patients suspected of having inflammatory bowel disease

Objective: This study was designed to evaluate the role of technetium-99m (Tc-99m) hexamethyl propylene amine oxime (HMPAO)-labelled leucocyte imaging as an initial screening test in patients suspected of having inflammatory bowel disease (IBD). Patients and methods: Thirty-one patients in whom a final diagnosis of irritable bowel syndrome (IBS) was made (group 1) and another 33 patients with established Crohn's disease (group 2) were studied. All patients had (TC)-T-99m HMPAO-labelled leucocyte scan with imaging al 40 and 120 min. Scans with abnormal bower uptake were considered positive and this uptake was quantified by visual grading and computer-based methods (scan score). Group 1 patients with positive Tc-99m HMPAO scan underwent an indium-111 ((111)ln)-labelled leucocyte scan (imaging at 180 min) followed by endoscopy and barium radiology as deemed necessary in order to verify the Tc-99m HMPAO result. Results: Three scan patterns were seen: well localized and unequivocally positive scans at both 40 min and 2 h were obtained from 28 patients. All but one had established Crohn's disease. Diffuse bowel uptake was seen in 14 scans. Ten of these (false positive) were obtained from symptomatic patients with IBS and four (false negative) from patients with asymptomatic Crohn's disease. No bowel uptake at 40 min and 2 h was seen in 22 scans. All but two of these (who had quiescent Crohn's disease) were obtained from patients with IBS. Active Crohn's disease is associated with significantly higher scan score (mean +/- SEM, 82.1 +/- 13.6) than the false positive scans (12.5 +/- 3.1, P greater than or equal to 0.001). Patients with false positive (TC)-T-99m HMPAO scans had negative In-111 scans, endoscopy and barium radiology. Conclusion: Bowel scanning using either In-111 or Tc-99m HMPAO is useful in excluding active IBD. Because of radiation dose, image quality and availability Tc-99m may be preferred to (111)ln.