Performance of the 20-minute whole blood clotting test in detecting venom induced consumption coagulopathy from Russell’s viper (Daboia russelii) bites

Abstract

The 20-minute whole blood clotting test (WBCT20) is used as a bedside diagnostic test for coagulopathic snake envenoming. We aimed to assess the performance of the WBCT20 in diagnosis of venom induced consumption coagulopathy (VICC) in Russell's viper envenoming. Adult patients admitted with suspected snake bites were recruited from two hospitals. WBCT20 and prothrombin time (PT) test were performed on admission. WBCT20 was done by trained clinical research assistants using 1 ml whole blood in a 5 ml borosilicate glass tube with a 10 mm internal diameter. The PT was measured by a semi-automated coagulation system and international normalised ratio (INR) calculated. VICC was defined as present if the INR was >1.4. The diagnostic utility of WBCT20 was determined by calculating the sensitivity and specificity of the WBCT20 on admission for detecting VICC. There were 987 snake bites where both WBCT20 and PT were done on admission samples. This included 79 patients (8 %) with VICC. The WBCT20 was positive in 65/79 patients with VICC (sensitivity 82 %; 95 % confidence interval [CI]: 72-90 %) and was falsely positive in 13/908 with no coagulopathy. The WBCT20 was negative in 895/908 snake bites with no coagulopathy (specificity: 98 % 95 % CI: 97-99 %) and was falsely negative in 14/79 with VICC. Using trained clinical staff, the WBCT20 test had a relatively good sensitivity for the detection of VICC, but still missed almost one fifth of cases where antivenom was potentially indicated.

Accuracy of the Lee–White Clotting Time Performed in the Hospital Routine to Detect Coagulopathy in Bothrops atrox Envenomation

“…Although these tests are used as diagnostic tools, they may not be readily available in resource-poor and isolated settings. 16 Instead, bedside whole-blood clotting tests have been used as a cheaper alternative for standard laboratory tests, such as the 20-minute whole-blood clotting test (WBCT20). 3,16,17 The Lee-White clotting time (LWCT), originally developed to monitor patients with hemophilia, has been used nationwide both as a diagnosis tool of snake venom-induced coagulopathy and to monitor antivenom therapy efficacy.…”

Smartphone-based infrared thermal imaging for differentiating venomous snakebites from non-venomous and dry bites

“…Dsilva et al observed that 24% of abnormal WBCT20 results were false-positive [4]. Rathnayake et al found that 13 of 908 snakebite patients with INR <1.4 had a false-positive WBCT20 [3]. In such situations, estimation of prothrombin time would be required.…”

“…Presence of regional lymphadenitis was also noted. One of the investigators (PS) performed a WBCT20 using a fresh clean borosilicate glass tube as described earlier [3]. Prothrombin time was tested in the clinical laboratory on blood samples collected into citrate tubes.…”

“…Prothrombin time was tested in the clinical laboratory on blood samples collected into citrate tubes. An international normalized ratio (INR) >1.40 was considered abnormal [3]. Decision to administer antivenom was made by the treating units in accordance with their usual practice.…”

“…However, clinical assessment of local swelling and warmth is often equivocal, especially when seen early on after a snakebite. Likewise, despite its simplicity, the WBCT20 suffers from frequent false-positive results leading to inappropriate use of precious antivenom [3,4]. Thus, there is an unmet need for a simple, rapid, and objective assessment tool that could differentiate venomous snakebites from non-venomous and dry bites.…”