Learning Center

Coagulation Corner

Pre-analytical Variables in Coagulation Testing - You haven't heard anything yet!

Laboratory medicine is typically divided into three main phases (preanalytical, analytical and postanalytical), Still with all of the advances in laboratory testing that have been made, lack of standardized in procedures for sample collection, patient preparation, specimen acquisition, handling and storage, account for up to 93% of the errors within the entire diagnostic process.

The complete elimination of laboratory testing errors is unrealistic, especially since errors relating to extra-analytical phases are harder to control.  When you add additional people to the mix, the difference between in- and out-patients, error rates (0.60% vs. 0.039%) is directly attributed to human factors related to skill in drawing blood and the sheer volume of laboratory tests carried out for inpatients. Non-laboratory personnel seems to account for the majority of errors, (95.2%). Data show that problems directly related to specimen collection are the main cause of preanalytical errors.  This further enhances the importance of Good Laboratory Practices and compliance with regulatory agencies as well as the practice of standard operating procedures.

So what defines a standard operating procedure?  That is a procedure that is written so well, a technologist running an assay can leave what they are doing, (or fall over) and a new tech can pick up (either them or the procedure) where they left off- there is no room for discussion. Everyone should be on the same page, with that being said, techs should have input on these procedures, they are the one who will be on the bench, they know what works and doesn’t.

Medical errors are the eighth leading cause of death exceeding those from traumatic accidents, breast cancer or AIDS, that is a lot of errors.  We all know how complex coagulation testing is, and as many times as it is said, pre-analytical variables account for many of the errors.  In fact since instrumentation is so improved, it has really made these pre-analytical errors the main factor influencing the quality of testing- sort of- we are talking about coagulation testing. We have reagents, buffers, calcium, deficient plasmas, standards, dilutions, inactivated factors that need to be activated, cofactors. Need I go on? So needless to say for coagulation testing, it is only amplified.

We know there are patient variables like age, gender, diet, smoking, alcohol intake, exercise, medication, physical & emotional stress those are the normal ones.  Lets now add, biological variation, blood type, genetic mutations, and ethnic groups! Ideas on how to control for that?

We also know about Specimen Variables: Order of draw, atraumatic blood draw. tube fill- over/under filled, platelet Poor Plasma and time to perform testing. Lets not forget pouring red tops into blue tops, sending EDTA samples for coagulation testing- just change the tube top, and what about the samples that sat at the nurses station for five hours and now require a stat APTT.  Of course my favorite are the removable clots, just take them out- don’t mean much at all. Manuals for that anyone.  Forget CSI, coagulation techs have better instincts and problem solving skills, they are true detectives. (CSI people wear better shoes then techs, but what does that tell you?)

So now let skip ahead to an age old topic - hemolysis- what do we do? So here are the issues -

Lab gets a sample, it is hemolyzed? Should we run it, how hemolized? Is it from in-vitro hemolysis (like a device or a bad draw) or is it in-vivo, like a burn patient or DIC? Vascular cell damage that occurs during phlebotomy, is the most frequent reason for specimen rejection, prevalence as high as 3.3%; five-fold more frequent than QNS.  In vitro hemolysis traditionally reflects a more generalized process of vascular and blood cell damage that can occur during phlebotomy, which causes cell membrane disruption and leakage of hemoglobin into the surrounding fluid.

Can you get that information? Okay stop laughing- we know you can’t-

So what do you do? Patient result, result may change course of treatment, good result, bad result? What to do?

Lets discuss -

We know to be ruthless about your specimen and results can only be as good as your sample.

The Clinical and Laboratory Standards Institute guidelines for prothrombin time (PT) and activated partial thromboplastin time (aPTT) testing states:

“ samples with visible hemolysis should not be used because of possible clotting, factor activation and  interference with endpoint measurement.”

Seems clear, HA -  so what do you do when the clinician says, give me the result, I will know what to do with it- clearly they were taught something about hemolysis that we were not- so here is my question:

 Does it shorten or prolong results?

Theory: Shorten:  may be caused by the exposure of anionic membrane phospholipids during erythrocytolysis which may provide a phospholipid-rich surface to accelerate coagulation reactions.

Theory: Prolong: exposure of membrane phospholipids could compete with thromboplastin for activated factor VIIa (FVIIa) availability and have the converse effect.

So you can pick a theory and make the results be what you would like. Also as you know hemolysis is subjective

• Hemoglobin < 20 mg/dL appear clear (nonhemolyzed) and those with a supernatant hemoglobin > 30mg/dL “hemolyzed.”

• Between 20 and 30 mg/dL in which the sample is questionable.

I know, I know results some times must be reported, and I know labs use messages stating that the results may be questionable due to hemolysis, suggest a re-draw etc etc ( everything but a skull and cross bones). However, I was at a meeting once and a lawyer/former tech addressed this issue- and the response made a lot of sense- If you were to testify in front of a jury of your peers (which is the operative word here) and you said that the result was sent because a clinician wanted it- well you are supposed to be the “expert” in laboratory testing.

Did you knowingly release a result that was possibly not correct?  Makes sense, makes me scared.  I have also been on the receiving end of a clinician needing those results -

So, just as laboratories are trying to minimize pre-analytical variables, more are discovered that impact coagulation results. All of this ensures job security.

The solutions that you come up with in your laboratory need to be standard and practiced by all.  I know hospitals that reject all hemolized samples, you need for everyone to be on board with that, including your pathologists. Not an easy issue, but remember you want the best result for patients.

I would like to wish you all a happy holiday and a happy and healthy 2011!

Enjoy the season.

Donna Castellone

About the Author

Donna Castellone,
MS, MT(ASCP)SH
View Complete Profile

Links

• Coagulation Corner
• Hemostasis Happenings
• New In Coagulation
• Coagulation Case Studies

Previous Posts

Archives