Search our site 
Advanced Search
Home | Exam dates | Contact us | About us | Testimonials |

You are in Home >> Resources >> Clinical anaesthesia >> Heparin Induced Thrombocytopaenia

Diagnosis of HIT

Created: 22/2/2007
Updated: 28/2/2007

Diagnosis of HIT

Laboratory testing is done when HIT is clinically suspected. Washed platelet activation assays and antigen assays are highly sensitive for diagnosis of HIT. Thus, negative testing by two sensitive and complementary assays (washed platelet activation assay and PF4-dependent enzyme immuno-assay) rules out HIT. Washed platelet activation assays have greater specificity compared with enzyme immuno-assays.


Factors influencing the frequency of HIT are summarised below:



Heparin type

Bovine lung UFH > porcine intestinal mucosal UFH > LMWH

Patient characteristics

Post-surgical > medical > obstetric patient

Duration of heparin

Fall in platelet count ‘begins’ between days 5-10, with thrombocytopaenic levels usually ‘reached’ by 7th-14th days

Dose of heparin

Change from prophylactic to therapeutic heparin doses can cause a drastic fall in platelet counts in the presence of HIT antibodies


Female > male

Definition of thrombocytopaenia used

Proportional thrombocytopaenia (>50% fall) is more sensitive for detecting HIT than absolute platelet count thresholds

SiteSection: Article

Related Articles:

  Posting rules

     To view or add comments you must be a registered user and login  

Login Status  

You are not currently logged in.
UK/Ireland Registration
Overseas Registration

  Forgot your password?

All rights reserved © 2021. Designed by AnaesthesiaUK.

{Site map} {Site disclaimer} {Privacy Policy} {Terms and conditions}

 Like us on Facebook