Dennis J. Ernst MT(ASCP), NCPT(NCCT)

Millions of patients are on blood thinners to prevent blood clots that can lead to stroke and other life-threatening complications. Because laboratory tests are critical to determine and monitor their dosage, drawing their blood regularly is essential to their well-being. Yet those who draw and handle their samples can easily and unknowingly alter the test results, leading to unnecessary and dangerous adjustments in their dosage. Do you know the multitude of ways in which you might unwittingly be misleading physicians into improperly medicating their patients? If you're a manager, does your staff know?

Phlebotomy Today recently polled three coagulation gurus in the laboratory industry for what they would most like anyone who draws coags to know to ensure all patients on blood thinners are properly medicated.

"Pre-analytical variables account for about 64% of coagulation errors," says Donna Castellone, supervisor of the Special Coagulation and Hematology department at New York Presbyterian-Columbia hospital in New York City. "So we want you to know a lot about drawing blood for coagulation testing. Everything starts with phlebotomy – garbage in- garbage out! Every improperly collected or handled sample can mean delayed surgery, additional testing or a change in medication."

Castellone can't underemphasize the importance of filling coag tubes properly. "With more and more automation, techs see less and less of the tubes prior to testing. They might not get rejected in the lab, so reject them at the point of collection. If you don't, it will impact your aPTT result. So, no underfilled tubes. This is really, really, really important.... Really!"

George Fritsma, MS, MT(ASCP), coagulation author, consultant, and purveyor of The Fritsma Factor, agrees. "An under-drawn 'short' specimen generates unreliable hemostasis results, so fill the tube to the fill line. Those who draw coags should not overfill the tube, either." He also warns of the risk of underfilling when collecting through an infusion set (butterfly needle).

"The tubing of the device delivers approximately 0.5 mL of air into the tube, causing a short draw," says Fritsma. He recommends applying a discard tube first, which may be another light blue-stopper citrate tube, but not a tube with another additive. "Plastic red-stopper or serum separator tubes contain particulate activators that can be transferred to the citrate tube."

Both gurus also concur on the importance of mixing citrate tubes immediately. "Telling people to mix well seems simple," says Castellone, "but if you don't, it will impact results. We don’t need frothing, just a nice mix." Fritsma joins the chorus by stressing tubes should be gently inverted 3-4 times to prevent clot formation, which makes coag results unreliable. He cautions against vigorous mixing, which hemolyzes red blood cells.

Fritsma also wants those who draw coags from existing IV lines to realize doing so often ruptures red blood cells, which is visible as pink to red plasma. Because hemolyzed specimens generate erroneous results for most laboratory tests, he discourages line draws. "If there is no other choice, collect blood slowly to reduce turbulence and lower the risk of hemolysis." Fritsma also stresses the importance of collecting and discarding 5 mL of whole blood to clear possible contaminants, then collect the hemostasis specimen.

Traumatic venipunctures are also a concern to Castellone. "If you have a difficult draw, it should be noted. You can activate factors with the introduction of tissue factor, and the results for screening tests may be artificially decreased, and factors increased."

Fritsma and Castellone not only want you to know the collection errors that threaten accurate coag results, but they're equally adamant that you know the handling errors that wreak just as much havoc on patient care. 
"Getting samples to the lab quickly is critical," says Castellone. "You only have a 4-hour window for the aPTT, and for patients on heparin it's only one hour. So get those samples to the lab ASAP."

Fritsma echoes her sense of urgency. "Immediately transport the hemostasis specimen to the laboratory at room temperature. Do not refrigerate them or place them on ice, and don't expose them to temperatures over 26oC. Chilling and heating both cause rapid specimen deterioration. Centrifuge and separate specimens that are collected to monitor heparin within one hour of collection."

For Castellone, how the labels are applied by the collector is something that often gets overlooked. "Labels... oh boy! If they are too thick they get stuck in the racks, if they overlap we can’t see patient information. Seems like a simple thing, but I have ruined more nails trying to scratch off labels to get info!"

Fritsma adds "Everyone who draws coags, or any sample for that matter, must label the tube with the patient’s full name, medical record number, and the date and time of collection while at the patient’s side. "And don't forget to follow the proper order of draw to prevent another tube's additive from carrying over into the coag tube, which could alter test results."

Fritsma hopes those who collect and handle coag samples realize they should observe the site for bleeding after the draw. "Many hemostasis patients take blood thinners and may require several minutes of post-venipuncture supervision and pressure bandages to prevent puncture site bleeding." He also states specimens for platelet function assays are never centrifuged or refrigerated, and testing must be completed within four hours.
Castellone recognizes the importance of phlebotomists and other healthcare professionals on getting good coag samples to the lab. "We appreciate all that you do, and how you help us start with a good sample, which is a really, really, really big deal!"

Participate in the conversation on ASCLS Connect and the Phlebotomy Scientific Assembly.

Reprinted with permission from Phlebotomy Today. © Center for Phlebotomy Education, Inc. Dennis J. Ernst MT(ASCP), NCPT(NCCT) is the director of the Center for Phlebotomy Education in Corydon, Indiana.