Bedside whole-blood clotting times: validity after snakebites

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.

We assessed two bedside methods for measuring whole-blood clotting time after snakebites for their congruence with results from a hospital laboratory.

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 ∼5 mL whole blood and looked for any clot formation within 20 min.

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.

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.