OctreoScan may cause false positives in diagnosing Crohn's disease

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In patients with Crohn’s disease, physicians should be aware the utilization of the imaging agent, OctreoScan, to detect neuroendocrine tumors, such as carcinoid tumors, may cause false positive results, according to an article published Sept. 14 in the World Journal of Gastroenterology.

Neuroendocrine tumors over express somatostatin receptors in their membranes, the authors wrote. Octreotide is an analogue whose molecule is a shortened version of somatostatin's with a high affinity for these receptors. The labeled form of octreotide is able to be imaged in scans (OctreoScan) and, therefore, pathological conditions overexpressing somatostatin receptors are easily recognized in this technique. Specifically, in the case of the detection of carcinoid tumors, OctreoScan has sensitivity nearly to 90 percent, according to the authors.

The research team, led by Alberto Fernandez from Povisa Hospital in Vigo, Spain, presented a case of a patient with a high suspicious of ileal carcinoid tumor (according to CT-scan and colonoscopy results) with a positive OctreoScan, showing uptake in the same bowel reported as pathological in CT. The patient underwent surgery and histological analysis reported Crohn's disease.

To explain the abnormal uptake in the OctreScan, immunohistochemical studies were performed, but the authors did not find somatostatine receptors in the sample.

According to the results, the authors could not find any explanation, and encouraged physicians to be aware that OctreoScan can cause of false positive results in diagnosing Crohn’s disease. The authors suggested that further studies should be made to assess the possible causes of the abnormal uptake.