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

 

Jordan Max Benjamin^1 2, Jean-Philippe Chippaux^2 3 4, Bio Tamou Sambo⁵, Achille Massougbodji¹ 

 

1 Center for the Study and Research of Malaria Associated with Pregnancy and Childhood (CERPAGE), 08 BP 841 Cotonou, Bénin

2 Whitman College, Department of Biology, Walla Walla, WA 99362, USA

3 IRD UMR216, Mère et enfant face aux infections tropicales, 75006 Paris, France

4 PRES Sorbonne Paris Cité, Université Paris Descartes, Faculté de Pharmacie, 75270 Paris, France

5 Département 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

 

Received: November 06, 2017.

Accepted: April 27, 2018.

 

Correspondence: jordanbenj@gmail.com

 

Authors’ contributions

JPC and AM conceived the study and designed the study protocol. JB and BT carried out the clinical monitoring and assessment. JB, JPC and AM carried out the analysis and interpretation of the data. JPC and JB drafted the manuscript. AM and BT critically revised the manuscript for intellectual content. All authors read and approved the final manuscript. JPC and AM are guarantors of the paper.

 

Competing interests

The authors declare that they have no competing interests.