Radiation Dose Prediction Using Data on Time to Emesis in the Case of Nuclear Terrorism

TLDR

Time‑to‑emesis for triage is problematic because it ignores non‑vomiting individuals, depends on differing exposure conditions, and can be confounded by psychogenic factors or emetic use. The study applies precision assessment to compute triage probabilities in nuclear‑terrorism scenarios and calls for more reliable post‑event dose‑assessment methods. The authors performed a rigorous statistical analysis of 108 retrospective radiation‑dose estimates from 1956‑2001 accidents, using standard error, confidence intervals, specificity, sensitivity, and ROC curves to characterize prediction uncertainty. The study found that time‑to‑emesis dose predictions have a relative error of ~200%, yielding a 95% confidence interval of roughly (D/4, 4D), and that its imprecision can cause a high false‑positive rate, so it should be used cautiously.

Abstract

A rigorous statistical analysis of the retrospective estimation of radiation dose received using time to emesis and its uncertainty is provided based on 108 observations associated with accidents with significant exposures to ionizing radiation in the period 1956-2001. The standard error, confidence interval, specificity and sensitivity, and Receiver Operating Characteristic (ROC) curve are used to characterize the uncertainty of the dose prediction. The relative error of the dose prediction using time to emesis data is about 200%. Consequently, if D is the dose assessment, the 95% confidence interval is approximately (D/4, 4D). Our assessment of the precision is applied to computation of the probabilities in triage medical management in the case of a nuclear terrorism event. We also note several factors that indicate that there are additional problems in the use of time to emesis for triage, including a lack of consideration of individuals that do not vomit, differences between the conditions under which the data were obtained and the conditions under which they are likely to be used, and the potential for the incidence of vomiting to be altered by factors unrelated to radiation exposure such as psychogenic factors and the use of emetic agents. In summary, while time to emesis is a rapid and inexpensive method for estimating the radiation dose, it should be used with caution because it is imprecise and may lead to a very high false positive rate. More reliable methods for after-the-fact assessment of radiation dose are needed to complement the use of time to emesis.