Features Partner Sites Information LinkXpress
Sign In
Advertise with Us

Tests Used to Measure Internal Bleeding Possibly Unreliable

By Labmedica International staff writers
Posted on 09 Sep 2015
Print article
The point-of-care INRatio PT/INR monitor system
The point-of-care INRatio PT/INR monitor system (Photo courtesy of Alere)
Internal bleeding may be uncommon as a result of taking blood thinners, but the normal coagulation tests physicians use to check for the side effect of bleeding may not be reliable.

Oral anticoagulants are administered at fixed daily doses, without the need for laboratory-guided adjustments, but there are limited data available on supratherapeutic doses or overdose of the oral Xa inhibitors and recently the clinical effect in patients exposed to rivaroxaban and apixaban has been characterized.

Scientists at the Nationwide Children’s Hospital (Columbus, OH, USA) and their colleagues carried out a retrospective study and collected data from more than 800 hospitals and eight regional poison centers covering nine USA states. Data were collected on patients who contacted one of the participating poison centers between January 1, 2012, and December 31, 2014. Data were recorded at the occurrence of the case by trained specialists such as nurses, pharmacists, or physicians, during the routine management of the exposure.

Of the 223 patients involved in the study, bleeding was reported in only 15 (7%), and coagulation tests were normal in most patients with bleeding, prothrombin time (PT) 83%, partial thromboplastin time (PTT) 83%, and international normalized ratio (INR) 44%. The PT was shown to be elevated in volunteer studies with rivaroxaban and also elevated in massive overdose. However results of the PT after use of blood thinners varied with different components. The effects of medications on the PTT are short lived and varies based on the reagents used. In patients with bleeding, PT and PTT were elevated in one of four with rivaroxaban and none with apixaban.

In a single case with measured serum rivaroxaban concentration, the PT was recorded as 126.3 seconds. Without specific clarification of methodology and reagent use, the PT and PTT may not reliably predict risk of bleeding after rivaroxaban or apixaban ingestion. The INR was elevated in only 21% of patients tested with rivaroxaban and in no patients with apixaban. In patients with bleeding, the INR was elevated in five of eight with rivaroxaban but in none with apixaban. The use of activated clotting time also appears to be insensitive after the use Xa inhibitors.

Henry Spiller, D.ABAT, a toxicologist and coauthor of the study, said, “One way to overcome the variation in these tests is to use anti-factor Xa chromogenic assays to measure Xa plasma concentrations; however these are not widely available and a potential drawback with measuring anti-factor Xa concentrations and plasma rivaroxaban and apixaban concentrations is that the turnaround time for results may be too long to guide a treatment plan.” The study was published on August 24, 2015, in the Annals of Emergency Medicine.

Related Links:

Nationwide Children’s Hospital 

Read the full article by registering today, it's FREE! It's Free!
Register now for FREE to LabMedica.com and get complete access to news and events that shape the world of Clinical Laboratory Medicine.
  • Free digital version edition of LabMedica International sent by email on regular basis
  • Free print version of LabMedica International magazine (available only outside USA and Canada).
  • Free and unlimited access to back issues of LabMedica International in digital format
  • Free LabMedica International Newsletter sent every 2 weeks containing the latest news
  • Free breaking news sent via email
  • Free access to Events Calendar
  • Free access to LinkXpress new product services
Click here to Register

ELITech Group


Copyright © 2000-2017 Globetech Media. All rights reserved.