Volume 198 - Issue 4
Tiger snake (Notechis spp) envenoming: Australian Snakebite Project (ASP-13)
Author: Alan Paul
Med J Aust 2013; 198 (4): 194. || doi: 10.5694/mja12.11538
Published online: 4 March 2013
Published online: 4 March 2013
Do the CSL snake venom detection kit dose recommendations need updating?
To the Editor: In their recent research paper, Isbister and colleagues questioned the clinical value of the CSL snake venom detection kit (sVDK) and the current approved dosing recommendations for CSL tiger snake antivenom (TSAV).1
They highlight five cases with a reported incorrect sVDK result for detection of brown snake rather than tiger snake venom. sVDK efficacy was not an end point of the trial and the methodology of how the kit was applied by the researchers was not described. Hence it remains unclear if a consistent collection approach was used by the researchers. Such variables can have a significant impact on conclusions.
The sVDK undergoes rigorous quality assurance testing and must meet batch release specifications before distribution. Data on sVDK specificity and sensitivity have been published supporting the robustness of the kit results when used as recommended.2 Training in the use of the sVDK is essential, and CSL conducts regular education sessions to optimise operator understanding and use of the kit.
Importantly, sVDK results should not be used in isolation in the clinical management of snakebite envenoming. Positive sVDK results only indicate the venom immunotype and are not an indication to give antivenom.3 Used in conjunction with clinical and laboratory evidence indicating envenoming has occurred, the sVDK helps in selecting the most appropriate monovalent product.3 When the clinical and laboratory findings do not correlate with sVDK results, urgent expert medical advice should be sought.
Isbister and colleagues suggest that one dose (one vial) of TSAV should be used to treat all tiger snake envenoming cases. This approach ignores differences in size between tiger snake species, extent of envenoming and patient comorbidities. Clinicians should be guided by a patient’s response to treatment and, in severe systemic tiger snake envenoming, several vials of antivenom may be required to control the effects, particularly if coagulopathy is present.4 CSL has long recommended higher doses than one vial for bites by some species of tiger snake that are far larger than the common mainland species and deliver higher doses of venom.5
Of further concern is the off-label recommendation that other non-tiger snake antivenoms may be used to treat tiger snake bites. Monovalent antivenoms undergo stringent testing to ensure that the neutralising capacity meets individual batch release specifications for the antivenom specified. There is no guarantee, batch to batch, that the undocumented neutralising capacity of other antibodies potentially present would be sufficient to treat snakebites not covered by that specificity. CSL does not recommend that these non-TSAVs be used in this way.
CSL encourages clinicians to continue using the sVDK and antivenoms according to the approved product information3,4 and in consultation with expert guidelines.
Competing interests
No relevant disclosures.
References
- Isbister GK, O’Leary MA, Elliott M, Brown SG. Tiger snake (Notechis spp) envenoming: Australian Snakebite Project (ASP-13). Med J Aust 2012; 197: 173-177. 0_CHDCCDAG
- Steuten J, Winkel K, Carroll T, et al. The molecular basis of cross-reactivity in the Australian Snake Venom Detection Kit (SVDK). Toxicon 2007; 50: 1041-1052. 0_i1142879
- CSL. Snake Venom Detection Kit product information. February 2007. http://www.csl.com.au/docs/92/398/SVDK_Product_Leaflet,0.pdf (accessed Feb 2013).
- CSL. Tiger snake antivenom product information. 21 January 2010. https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2010-PI-05203-3 (accessed Feb 2013).
- White J. CSL antivenom handbook. Melbourne: CSL, 2001: 38. http://www.toxinology.com/generic_static_files/cslavh_antivenom_tiger.html (accessed Feb 2013).