A Randomized, Double-blind, Sham-controlled Trial Comparing Two Screening Devices for Radiation Contamination

Objectives: This exploratory study compared the screening ability of a newly introduced radiation detection portal with a traditional Geiger counter for detection of radiation contamination in the setting of a mass casualty training exercise. Methods: Following a pretrial evaluation of interobserver reliability for Geiger counter use, 30 volunteers were randomly assigned to don gowns containing three disks, each of which was either a sham resembling the radioactive samples or an actual cesium-137 sample; each subject participated a minimum of four times with different gowns each time. Each subject underwent standard radioactivity screening with the Geiger counter and the portal. Results: Interobserver reliability was excellent between the two Geiger counter screeners in the pretrial exercise, correctly identifying 101 of 102 sham and radioactive samples (kappa = 0.98; 95% confidence interval [CI] = 0.94 to 1.00). For radioactively labeled subjects across all bodily locations, the portal (43/61, or 70.5%; 95% CI = 58.1% to 80.5%) was less sensitive than the Geiger counter screening (61/61, or 100%; 95% CI = 92.9% to 100%), which resulted in a portal false-negative rate of 29.5%. For radiation detection in the posterior thorax, the portal radiation screening (4/19, or 21.1%; 95% CI = 8% to 43.9%) was less accurate than the Geiger counter (19/19, or 100%; 95% CI 80.2% to 100%). In contrast, there were no major differences between the portal and the Geiger counter for radiation detection at the left shoulder, right shoulder, or sham (nonradiation) detection. There were no false-positive detections of the sham-labeled subjects for either device, yielding a specificity of 100% for both screening modalities. Conclusions: Geiger counter screening was more sensitive than, and equally specific to, radiation detection portal screening in detecting radioactively labeled subjects during a radiation mass casualty drill. ACADEMIC EMERGENCY MEDICINE 2010; 17:1020-1023 (C) 2010 by the Society for Academic Emergency Medicine.