title: Diagnostic 20-min whole blood clotting test in Russell's viper envenoming delays antivenom administration.
abstract: BACKGROUND
  The 20-min whole blood clotting test (WBCT20) is widely used for the identification of coagulopathy in snake envenoming, but its performance in practice has not been evaluated.
  
  
  OBJECTIVE
  We aimed to investigate the diagnostic utility of the WBCT20 for coagulopathy in Russell's viper envenoming.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Adult patients with snake envenoming were recruited. Age, sex, bite information, clinical effects, serial WBCT20 and antivenom treatment were recorded. Definite Russell's viper envenoming was confirmed with venom specific enzyme immunoassay. We assessed sensitivity of admission WBCT20 to coagulopathy (international normalized ratio, INR > 1.5) in Russell's viper envenoming, the specificity of negative WBCT20 in non-envenomed patients and directly compared paired WBCT20 and INR.
  
  
  RESULTS
  Admission WBCT20 was done in 140 Russell's viper bites with coagulopathy and was positive in 56/140 [sensitivity 40% (95% confidence interval (CI): 32-49%)]. A negative WBCT20 led to delayed antivenom administration [WBCT20-ve tests: median delay, 1.78 h (interquartile range (IQR): 0.83-3.7 h) vs. WBCT20 + ve tests: median delay, 0.82 h (IQR: 0.58-1.48 h); P = 0.0007]. Delays to antivenom were largely a consequence of further WBCT20 being performed and more common if the first test was negative (41/84 vs. 12/56). Initial WBCT20 was negative in 9 non-envenomed patients and 48 non-venomous snakebites [specificity: 100% (95% CI: 94-100%)]. In 221 paired tests with INR > 1.5, the WBCT20 was positive in 91(41%). The proportion of positive WBCT20 only increased slightly with higher INR.
  
  
  CONCLUSIONS
  In clinical practice, the WBCT20 has low sensitivity for detecting coagulopathy in snake envenoming and should not over-ride clinical assessment-based decisions about antivenom administration. There is an urgent need to develop a simple bedside test for coagulopathy in snake envenoming.
authors.affiliation: Department of Clinical Toxicology and Pharmacology, Calvary Mater Newcastle, Edith St, Waratah, NSW 2298, Australia. geoff.isbister@gmail.com.
authors.forename: G K
authors.initials: GK
authors.lastname: Isbister
authors.forename: K
authors.initials: K
authors.lastname: Maduwage
authors.forename: S
authors.initials: S
authors.lastname: Shahmy
authors.forename: F
authors.initials: F
authors.lastname: Mohamed
authors.forename: C
authors.initials: C
authors.lastname: Abeysinghe
authors.forename: H
authors.initials: H
authors.lastname: Karunathilake
authors.forename: C A
authors.initials: CA
authors.lastname: Ariaratnam
authors.forename: N A
authors.initials: NA
authors.lastname: Buckley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000997:Antivenins / Q000627:therapeutic use; D001777:Blood Coagulation; D005260:Female; D006801:Humans; D007155:Immunologic Factors; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D017840:Daboia; D012909:Snake Bites / Q000097:blood / Q000175:diagnosis* / Q000628:therapy; D013188:Sri Lanka / Q000453:epidemiology; D016896:Treatment Outcome; D014757:Viper Venoms; D055815:Young Adult
chemical_list: D000997:Antivenins; D007155:Immunologic Factors; D014757:Viper Venoms