If, as was defined, “a strong pulse is considered ‘normal’ then an ‘abnormal’ pulse would be one that is not strong (ie, weak or absent).” Hence, an abnormal radial pulse would be considered a positive test result and a normal radial pulse considered a negative test result. On the other hand, likelihood ratios were also reported, which are very appropriate for judging the utility of a diagnostic test such as pulse quality, though it may not be clear to all readers how these were calculated or what their implications for TCCC may be.Ī 2 × 2 table can be constructed from data presented in Table 3 of the article. In the analysis by Naylor et al., subjects were exposed to a wide variety of potential causes of hypotension so, with respect to risk, two comparable groups did not exist. Relative risk represents a ratio of the probabilities of a defined outcome in one group exposed to a risk factor to another group having the same outcome yet not exposed to the same risk factor. The former is not appropriate for a diagnostic test. From their data, the authors calculated relative risks and likelihood ratios. Naylor and his coinvestigators reported three pulse qualities (strong, weak, or absent) then correlated them to systolic blood pressure (SBP) being <80 mmHg or ≥80 mmHg. Because the probability of that impression being correct or incorrect is rarely 0 or 1-more commonly referred to as 0% or 100%-clinical decisions must be made on how likely being correct may be.Īny scientific article on diagnostic test performance should report likelihood ratios, because these assist decision-makers in converting a pre-test probability of a condition such as shock being present into a post-test probability that may or may not exceed thresholds for initiating or withholding action. For the most part, each supplies a binary result of either “present” or “absent”-or, alternatively, “positive” or “negative.” Each data element acquired during casualty assessment, alone or in combination, contributes to a clinical impression. Every observation related to the mechanism of injury, every question asked of a patient or bystander, and every component of a physical examination is a diagnostic test. Gathering any data point for purposes of aiding a clinical decision is a diagnostic test, even if not an imaging or laboratory “test” and even if not ascribing a “diagnosis” to a patient. For instance, the 2019 Tactical Combat Casualty Care (TCCC) guidelines 2 employ a “weak or absent radial pulse” as a surrogate marker of shock, the presence of which influences decisions related to volume resuscitation. Whether or not pulse quality contributes to casualty assessment has important implications for all levels of care when a manometer is not available, because it could drive actions such as clinical intervention. In this month’s issue of Military Medicine, Naylor and colleagues 1 have contributed a retrospective association of radial pulse quality and hypotension in a Department of Defense Trauma Registry dataset.
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