title: Improved detection and localization of lower gastrointestinal hemorrhage using subtraction scintigraphy: clinical evaluation.
abstract: Does subtraction scintigraphy improve the diagnostic utility of scintigraphic evaluation in acute lower gastrointestinal hemorrhage?
  
  
  METHODS
  This research was a retrospective clinical study using a repeat-measures design of randomized control and experimental groups. A single patient dataset provided both the control group (conventional scintigraphy) and the experimental group (conventional and subtraction techniques). Forty-nine raw (99m)Tc-red blood cell studies were randomized and interpreted by 4 independent physicians as conventional scintigraphy data only (round 1). The conventional scintigraphy studies were combined with subtraction images and randomized for reinterpretation (round 2).
  
  
  RESULTS
  Although there was a decrease in the mean, no statistically significant difference was noted between the mean time to bleed detection between interpretive rounds 1 and 2 (P = 0.524). The addition of subtraction scintigraphy to the interpretation process changed the outcome from "probably present" to "absent" for 14% of patients and from "equivocal" to "absent" for another 12%, and this change had a marked effect on the false-positive rate. The false-positive rate decreased from 9.6% in round 1 to 3.6% in round 2. Receiver operator characteristic analysis showed that combining conventional scintigraphy with subtraction scintigraphy improved test performance.
  
  
  CONCLUSIONS
  False-positive studies can be reduced by using subtraction scintigraphy in conjunction with conventional scintigraphy in the interpretive process.
authors.affiliation: School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, Australia. gcurrie@csu.edu.au
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Currie
authors.forename: Philip A
authors.initials: PA
authors.lastname: Towers
authors.forename: Janelle M
authors.initials: JM
authors.lastname: Wheat
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006471:Gastrointestinal Hemorrhage / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013382:Subtraction Technique