Specificity of somatostatin receptor scintigraphy: a prospective study and effects of false-positive localizations on management in patients with gastrinomas.
Somatostatin receptor scintigraphy (SRS) is being increasingly used both for localization and, in some cases, diagnosis of various diseases. There are no prospective studies of its specificity or occurrence of false-positive results and their effects on management. This study was designed to address both of these issues.


METHODS
Over a 40-mo period, 146 consecutive patients with Zollinger-Ellison syndrome (ZES) undergoing 480 SRS examinations were studied prospectively. Patients were admitted at least yearly and underwent SRS as well as conventional imaging studies (ultrasonography, CT, MRI) and angiography, if necessary. All admissions were assigned to one of five different clinical categories in which imaging studies had different purposes. SRS localizations were classified as true-positive or false-positive based on preset criteria. A false-positive result was determined to change clinical management based on five preset criteria.


RESULTS
Of all SRS examinations, 12% resulted in a false-positive localization for a neuroendocrine tumor or its metastases, resulting in a sensitivity of 71%, specificity of 86% and positive and negative predictive values of 85% and 52%, respectively. Extra-abdominal false-positive localizations (2/3) were more common than intra-abdominal (1/3). Thyroid disease, breast disease and granulomatosis lung disease were the most frequent causes of extra-abdominal false-positive localizations. Accessory spleens, localization to previous operative sites, renal parapelvic cysts and various procedural aspects were the most frequent causes of intra-abdominal false-positive localizations. Of all SRS studies, 2.7% resulted in a false-positive result that altered management.


CONCLUSIONS
False-positive SRS localization occurs in 1 of 10 patients with ZES. By having a thorough understanding of diseases or circumstances that result in false-positive localization and comparing the SRS result with the clinical context, the percentage of patients in whom false-positive localization results in altered management can be reduced to below 3% and the correct diagnosis made in almost every case.
Gibril
F
F
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-1804, USA.
Reynolds
J C
JC
Chen
C C
CC
Yu
F
F
Goebel
S U
SU
Serrano
J
J
Doppman
J L
JL
Jensen
R T
RT
D005189:False Positive Reactions; D005260:Female; D015408:Gastrinoma / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000601:surgery; D006801:Humans; D007205:Indium Radioisotopes; D008113:Liver Neoplasms / Q000453:epidemiology / Q000556:secondary; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin / Q000032:analysis*; D012680:Sensitivity and Specificity; D013670:Sodium Pertechnetate Tc 99m; D013004:Somatostatin / Q000031:analogs & derivatives; D013997:Time Factors; D015043:Zollinger-Ellison Syndrome / Q000000981:diagnostic imaging* / Q000453:epidemiology
D007205:Indium Radioisotopes; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D013004:Somatostatin; D013670:Sodium Pertechnetate Tc 99m; C081788:pentetreotide