Another Reason Why Lab Draws Are Not Better

[Guest]

See: Delate T. Chest 2007;131:816-822. Falsely Elevated International Normalized Ratios in Patients Undergoing Anticoagulation Therapy.

This is from Kaiser in Denver. They currently have over 6,800 people in their anticoagulation service and monitor them using venous blood draws. They have found that collecting the blood in pediatric tubes and being on hemodialysis are common reasons for people to have INRs greater than 10 for no known reason. They found that this happened 108 times in the four year study period.

 

[Karlynn]

Thanks Al. I think sometimes people think I'm a little nuts for saying that I don't believe that Lab INR's should always be considered the best basis for comparison with a home machine in checking it's accuracy. I think it's just one way to check accuracy - not always the best way. With lab draws there can be variables thrown in the testing "chain of custody" that the patient doesn't see that can impact the accuracy of the INR.

 

[Ross]

While Doctors hold these labs up as Gold Standards, it just makes me realize how much less they understand the drug. Look around, there isn't any machine nor lab instrument that is perfect at producing results for INR. I have yet to see a lab get the same reading twice with the same sample, but to hear them tell it, it does.

 

[Guest]

Every three months we test our CoaguCheks against eith our lab's testers or a standard form a testing company. Seldom do all three tests agree to the exact 0.X INR unit.