2025/01/20 by R. Aaron Bola, Rana Biary · 1 voice
Medicine · Decision Sciences · #Traumatic Brain Injury and Neurovascular Disturbances #Meta-analysis and systematic reviews #Radiation Dose and Imaging
paper · pdf · doi:10.1111/1742-6723.14561
openalex publication_date 2025/01/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We read with interest the article by Lousick et al. published in Emergency Medicine Australasia.1 In their retrospective analysis, the authors reported a zero yield for computed tomographies of the brain (CTB) ordered without a clear clinical indication other than intubation because of overdose. We believe that this result should be interpreted very cautiously, and warrants a statistical reminder for clinicians regarding zero numerators reported in medical literature. In their seminal 1983 paper,2 Hanley and Lippman-Hand assert that when a study demonstrates zero numerators, the confidence intervals between zero and a certain upper limit must be reviewed. They describe the rule of three: ‘if none of n patients showed the event about which we are concerned, we can be 95% confident that the chance of this event is at most 3 in n (i.e., 3/n)’. This formula provides the upper limit of the 95% confidence interval (CI) for 0/n rates reported in the literature. Lousick et al. reported that the CTB yield for patients where no clinical indication for imaging was documented was 0/121, or 0%. Using the rule of three as described above, the upper limit of the 95% CI for this result is 3/121, or 2.5%. While still lower than the reported CTB yield for patients where a clinical indication for imaging was documented (2/38, or 5%), this calculation provides an alternative perspective for interpreting their results. The reported zero yield in this series may not mean that there is no indication to perform a CTB. We agree with Lousick and colleagues in advocating for interdepartmental dialogue when deciding to pursue CTBs for patients who have overdosed. We also agree that not all patients who are intubated following an overdose require a CTB. However, taking into consideration the statistical concept reviewed above, we disagree with their conclusion that CTB for intubated overdose patients without clinical indication is ‘unjustified’. A certain event not occurring in a series, particularly one with a small sample size of 121 patients, does not mean it will never happen. It most certainly can, and its rate of occurrence can be inferred from its 95% CI. None declared.