Delayed double reading of whole blood clotting test (WBCT) results at 20 and 30 minutes enhances diagnosis and treatment of viper evenomation

Journal of Venomous Animals and Toxins including Tropical Diseases, Feb 2019

Jordan Max Benjamin, Jean-Philippe Chippaux, Bio Tamou Sambo, Achille Massougbodji

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Delayed double reading of whole blood clotting test (WBCT) results at 20 and 30 minutes enhances diagnosis and treatment of viper evenomation

Research Delayed double reading of whole blood clotting test (WBCT) results at 20 and 30 minutes enhances diagnosis and treatment of viper evenomation Jordan Max Benjamin1  2  *  Jean-Philippe Chippaux2  3  4  Bio Tamou Sambo5  Achille Massougbodji1  1Center for the Study and Research of Malaria Associated with Pregnancy and Childhood (CERPAGE), 08 BP 841 Cotonou, Bénin 2Whitman College, Department of Biology, Walla Walla, WA 99362, USA 3IRD UMR216, Mère et enfant face aux infections tropicales, 75006 Paris, France 4PRES Sorbonne Paris Cité, Université Paris Descartes, Faculté de Pharmacie, 75270 Paris, France 5Département de chirurgie et spécialités, Faculté de Médecine, Université Parakou, Parakou, Bénin Abstract Background The whole blood clotting test (WBCT) is a simple test of coagulation that is often used in the assessment, diagnosis, and therapeutic monitoring of snakebite patients in sub-Saharan Africa. WBCT requires only a clean glass tube and several milliliters of venous blood and is ideal for use in poorly equipped health centers throughout the rural areas where 95% of snakebites occur. However, questions surrounding the accuracy and reliability of the test remain unanswered due to variations in testing conditions and a lack of comparative research with which to validate them. This is the first study to evaluate WBCT results at both 20-min (WBCT20) and 30-min (WBCT30) reading times in the same group of snakebite patients. Methods In order to define the best reading time, the authors compared the results of serial WBCT evaluation at both 20 and 30 min after collection in 23 patients treated for snake envenomation in Bembèrèkè, northern Benin. Results WBCT results were identical at both reading times in patients without coagulopathy or when coagulation was restored permanently following a single dose of antivenom. Out of 17 patients with coagulopathy, 14 showed discrepancies between WBCT20 and WBCT30 results in at least one pair of serial evaluations. These could be completely contradictory results (e.g. normal clot at WBCT20 and no clot at WBCT30) or a marked difference in the quality of the clot (e.g. no clotting activity at WBCT20 and an unstable partial clot at WBCT30). WBCT discrepancies were encountered most frequently in three situations: initial normalization of hemostasis following antivenom therapy, detection of a secondary resumption of coagulopathy, or final restoration of hemostasis after a secondary resumption had occurred. Conclusions This study suggests that the WBCT is robust and that a sequential reading should improve the diagnosis and monitoring of venom-induced coagulopathies. It also indicates the possibility of discrepancies in the sensitivity of WBCT20 and WBCT30 for detecting the resolution or reoccurrence of coagulopathy and identifies how these findings, if confirmed, may be used to increase the efficacy and efficiency of antivenom treatment in the field. Keywords Africa; Snakebite; Echis; Envenomation; Whole blood clotting test; WBCT; Venom-induced consumption coagulopathy; Carpet viper; Saw-scaled viper Background In developing countries, particularly in sub-Saharan Africa, most envenomations occur in rural areas and are managed in peripheral health centers lacking the capability to perform automated laboratory tests for diagnosis or monitoring of envenomed patients [1, 2]. Venom-induced consumption coagulopathies (VICC) are present in more than two-thirds of African snake envenomations [3]. When used correctly, the whole blood clotting test (WBCT) is a simple, effective, affordable bedside examination that provides valuable information during initial assessment and ongoing management of snakebite patients throughout the course of treatment [4–7]. Use of the WBCT for detecting VICC in snakebite patients was standardized by Sano-Martins et al. [8]. It requires collection of a small amount of venous blood (about 2 mL) in a dry and clean glass tube to evaluate the coagulation time by simple direct observation of clot formation and stability 20 min after collection. Several field studies have confirmed that the WBCT was sufficiently sensitive and specific to be of clinical value [4, 5, 9–11]. It is a comprehensive blood test to diagnose and monitor coagulopathy in patients bitten by most viper species, which is valid throughout the world. It is also useful for diagnosis of coagulopathy in patients bitten by dangerous colubrids and many of the elapid species found in Australasia. The WBCT is particularly useful when the symptoms are mild or before the onset of clinical hemorrhagic syndrome [5, 6, 9, 12]. In addition, the WBCT is an important criterion for evaluating the efficacy of antivenom therapy [3, 9, 13, 14]. The test should be carried out in a clean, dry, glass tube completely free of detergent. Deviations from this protocol such as the use of poorly rinsed glassware or a (...truncated)


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Jordan Max Benjamin, Jean-Philippe Chippaux, Bio Tamou Sambo, Achille Massougbodji. Delayed double reading of whole blood clotting test (WBCT) results at 20 and 30 minutes enhances diagnosis and treatment of viper evenomation, Journal of Venomous Animals and Toxins including Tropical Diseases, 24, DOI: 10.1186/s40409-018-0151-1