Comparison of bedside clotting tests for detecting venom-induced consumption coagulopathy following Sri Lankan viper envenoming

Abstract

Background

The whole blood clotting test (WBCT) is commonly used for diagnosing venom-induced consumption coagulopathy (VICC) in resource-poor settings. We aimed to investigate the diagnostic accuracy of the WBCT and capillary blood clotting test (CBCT) for detecting VICC in viper envenoming in Sri Lanka.

Methods

All confirmed snakebites admitted to Teaching Hospital Anuradhapura from July 2020 to June 2021 were included. On admission, WBCTs after 15, 20 and 25 min observation times (WBCT-15, WBCT-20 and WBCT-25) and CBCT observed in 30 s intervals (CBCT-t), 5 and 10 min CBCT (CBCT-5 and CBCT-10) were done. Blood was collected simultaneously for prothrombin time (PT)/international normalized ratio (INR) and plasma fibrinogen. We defined VICC as an INR >1.5 (Incomplete VICC = INR>1.5 and complete VICC = ≥3.0).

Results

A total of 272 confirmed snakebites (Russell’s viper[76], hump-nosed viper[89], non-venomous snakes[51] and unidentified bites[56]) were recruited (median age: 42 y [interquartile range: 30- 53 y]; 189 males [69%]). On admission, 82 (30%) had incomplete VICC (INR >1.5 and <3) and 77 (28%) had complete VICC (INR ≥3). Sixteen (6%) developed clinically apparent bleeding. The WBCT-15 had the best sensitivity of 47% for detecting VICC and 68% for complete VICC. The sensitivities of the WBCT-20, WBCT-25, CBCT-5 and CBCT-10 was 30–35%. The sensitivities of all tests were better in detecting complete VICC, VICC in Russell’s viper bites and more than 2 h post-bite. The WBCT-15 test had a sensitivity of 76% for VICC in confirmed Russell’s viper bites. For detection of VICC, CBCT-t had an an excellent sensitivity of 97%, but a poor specificity of 35% for an optimal cut-off of >6.25 min.

Conclusion

WBCTs are poorly diagnostic for VICC in Russell’s viper and hump-nosed viper envenoming, missing up to two-thirds of patients for some tests. The WBCT-15 was the best test, improving for more severe VICC and greater than 2 h post-bite.

Keywords:

• Sri Lanka
• snakebite
• viper envenoming
• whole blood clotting tests
• capillary blood clotting tests
• venom-induced consumption coagulopathy

Acknowledgements

The authors acknowledge the support of all the consultant physicians, medical officers and nursing officers at Teaching Hospital Anuradhpura during the study period. The authors sincerely thank all the clinical research assistants for assisting with clinical data collection, Umesh Chathuranga, Dilani Pinnaduwa, Shahmy Sayed, and Fahim Mohamed for assisting with logistics (South Asian Clinical Toxicology Research Collaboration), and staff of the Department of Parasitology, Faculty of Medicine and Allied Sciences-Rajarata University of Sri Lanka.

Author contributions

SW, AS and GI designed the study; SW, SS and KS identified patients; SW did the data extraction; SW, AS and GI carried out the analysis of the data; SW did the literature review; SW drafted the manuscript. All authors read and approved the final manuscript. GI is guarantor of the paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study is funded by National Health and Medical Research Council [1110343 and 1154503] and Rajarata University of Sri Lanka (RJT/R & PC/2021/R/FMAS/03).