Bedside whole-blood clotting times: validity after snakebites

<p>BACKGROUND: Venomous snakebites contribute to morbidity and mortality throughout the world, most commonly in resource-poor areas, with about 2.5 million humans sustaining snakebites annually. Coagulopathy is a significant cause of both morbidity and mortality in these patients. In the absence of more sophisticated hematological studies or obvious physical findings, many clinicians must rely on whole-blood clotting times to assess whether their patients are coagulopathic. Alternative (bedside) methods to assess clotting times are often officially recommended and used, but have not been validated. OBJECTIVE: We assessed two bedside methods for measuring whole-blood clotting time after snakebites for their congruence with results from a hospital laboratory. METHODS: Over a 5-month period, 46 sequential patients presenting with a possible snakebite had blood drawn for bedside (using syringe and ceftriaxone bottle as containers) and laboratory whole-blood clotting tests. All three tests used approximately 5 mL whole blood and looked for any clot formation within 20 min. RESULTS: Compared to the laboratory, the syringe method correctly classified the patients 84.7% of the time (sensitivity 88.9%; specificity 82.4%). The bottle method correctly classified the patients 86.8% of the time (sensitivity 83.3%; specificity 90.0%). Comparing the area under the Receiver Operator Characteristics curves shows that both the syringe and bottle methods do not differ in their discrimination for identifying clotting. CONCLUSIONS: Both the syringe and ceftriaxone bottle bedside clotting test methods appear to be accurate enough to help guide therapy after potential snake envenomations when formal laboratory testing is unavailable.</p>