Garbage In; Garbage Out: Part VII
Last month, we discussed how delays in specimen processing alter test results. (To access this and other archived issues, visit http://www.phlebotomy.com/PTSTAT.html.) This month we will continue with how improper or inadequate centrifugation can turn specimens… and the results that come from them… into garbage.
But while you're doing the hokey pokey, are you sure the cells are separating properly? To be sure, anyone who processes specimens for laboratory testing has to know a little bit about centrifugation physics.
Proper centrifugation is not just about how many times the specimen spins every minute (rpms), it's about the force of gravity that it subjects the tube to. It's the g-force, also known as rcf or relative centrifugal force (or field) that actually separates the serum from the cells. Every model of centrifuge delivers a g-force that is dependent upon its design. Put specimens from the same patient into two different models, spin them at the same rpm for the same amount of time, and it's likely that the degree to which cells have been removed from the serum or plasma will be different. The serum/plasma from one may be acceptable for testing while that of the other may not.
The g-force exerted by a centrifuge depends upon the distance from the rotor of the centrifuge (the vertical post that spins the buckets or sleeves holding the specimens) to the bottom of the collection tube when it is furthest from the rotor while spinning. The greater the distance between the rotor and the tube's bottom, the greater the g-force and the better the separation. What happens when separation is inadequate? You create garbage for the laboratory to test, and they report garbage results to the physician.
If the tube contains a gel barrier (i.e., serum separator), spinning at the proper rcf is critical so that the gel functions properly. A gel barrier liquefies when exposed to the proper g-force, and migrates through the cells during centrifugation eventually positioning itself between the liquid and cellular components of blood. (In case you're ever on a game show or play Scrabble avidly, the term for this property is thixotropic.) If a serum tube with a gel separator is spun under conditions that exert a g-force upon the specimen less than what the manufacturer recommends, the gel will not properly position itself between the cells and serum. As a result, the serum contains cellular components that threaten the laboratory's ability to extract an accurate test result from the specimen.
Cells, clots, and potassium
Likewise if clotting continues after centrifugation. As blood clots, platelets release potassium into the serum. Therefore, when platelets are in excess above the gel due to insufficient separation, they work to falsely elevate the patient's reported potassium level just as red cells will. Depending on a multitude of variables, the difference between the patient's actual potassium level and that reported to the physician can be significant enough to change the way the patient is managed. Patients who truly have a low potassium level can appear as normal and go untreated, while those with normal levels can appear abnormally high, prompting physician intervention when it isn't necessary. All because of improper centrifugation.
Platelets can also remain above the gel when centrifugation is rushed, as when clot activator tubes are spun before the specimen is clotted. Complete clotting can take up to 30 minutes, even tubes with a clot activator. All who centrifuge blood specimens must be aware that clot activators facilitate complete clotting, not necessarily faster clotting. Many who process specimens mistakenly think that if the blood in a tube no longer flows when inverted, clotting is complete and it can be centrifuged. More than likely, such thinking produces specimens with thick mats of fibrin above the gel barrier, forcing specimen processors to rim the clot (exposing themselves to bloodborne pathogens and hemolyzing red blood cells), and recentrifuge the tube. Not only do tube manufacturers discourage recentrifugation, so does the Clinical and Laboratory Standards Institute.(1) Remember, just because a clot-activator tube becomes gelatinous doesn't mean it is ready to centrifuge. Complete clotting takes up to 30 minutes even for clot-activator tubes.
Swivel or fixed?
When serum-separator tubes are centrifuged at a fixed angle, the gel barrier will not be evenly dispersed. One side of the barrier will be thick; one perilously thin. Should the thin side permit serum and cell contact, altered test results, especially potassium, are possible. Facilities unable to switch from a fixed-angle centrifuge to a swivel-head model to eliminate the centrifuge's contribution to erroneous potassium results should consider using tubes with twice the gel. So-called “double gel” tubes can provide enough gel to prevent exposure between serum and cells when using a fixed-angle centrifuge.
How can those who centrifuge blood specimens help patients be treated according to accurate results? By making sure all tubes are spun according to the manufacturer's recommended g-force for the recommended length of time. Most centrifuges are carefully monitored, maintained, and calibrated by the designated laboratorian or biomedical engineer. The College of American Pathologists (CAP) recommends centrifuges be checked for timer accuracy monthly and at least quarterly for rpms. When rpms are checked, it is an opportune time to confirm the centrifuge's g-force conforms to the tube manufacturer's recommendation.
If your centrifuge isn't spinning tubes adequately, you could be putting garbage into the tube, essentially guaranteeing the lab's testing personnel are taking garbage out in the form of inaccurate results. So make sure you are centrifuging specimens properly. Check the g-force your centrifuges deliver; know what the tube manufacturer recommends; don't turn off the centrifuge prematurely; use swivel-head centrifuges whenever possible; and use double-gel tubes when fixed-angle centrifuges don't provide a good gel barrier. If you pay attention to all these factors, you can be sure that while you're busy doing the hokey pokey, there will be no doubt the cells are separating like they should inside the centrifuge. That's what it's all about.
Next month: Storage and add-on requests.
This Month in Phlebotomy Today
Here's what subscribers to Phlebotomy Today, the Center for Phlebotomy Education's paid-subscription newsletter currently in its 9th year of publication, are reading about this month:
For subscription rates and to subscribe to Phlebotomy Today, visit www.phlebotomy.com/PhlebotomyToday.html. The current month's issue will be emailed to you immediately upon subscribing.
Haitian Ministry Recruiting Phlebotomists
Randolph World Ministries, Inc. is looking for a few good phlebotomists. The ministry, founded by St. Louis University clinical laboratory science professor Tim Randolph, assists Haitian laboratories to provide basic laboratory services to their citizens.
“Our annual trips to Haiti have made tremendous strides towards basic laboratory services to this impoverished country,” says Randolph, who has been taking supplies and a growing team of medical professionals to Haiti since 2000. “It is becoming increasingly obvious that the Haitian labs we serve would benefit enormously if our teams would include phlebotomists to perform venipunctures and/or conduct train-the-trainer workshops.”
Randolph's teams visit Haiti twice per year, and conduct a health clinic every June.
“Phlebotomists are desperately needed to draw blood during the annual basic health screening and during the mobile clinics we conduct,” says Randolph. Last year, the team grew to 12, the largest contingency Randolph has assembled so far. They have successfully helped labs correct errors in testing procedures and introduce new and critical laboratory tests such as sickle cell, bilirubin, H. pylori, Hepatitis B, and body fluid analyses.
Randolph hopes phlebotomists looking for ways to use their skills in new and challenging ways will consider volunteering for the June trip.
“The potential for personal growth and satisfaction is incredible,” says Randolph. “The June trip is four weeks in length, but individuals only able to make a two-week commitment will be considered.”Since the ministry relies on donations of time and talent, not revenue, to accomplish its mission, team members pay their own expenses. The typical expense for a two-week trip is approximately $1,200/person and the entire four-week trip will cost approximately $1,600 (excluding the cost of immunizations, passport, and travel to and from Ft. Pierce, Florida). Interested phlebotomists or other healthcare professionals with specimen collection expertise can contact Randolph at www.randolphworldministries.org.
Featured FAQ: Average Bruise Rate
Q: Do you have a source for what the average bruise rate should be when performing phlebotomy?
A: A Q-Probe published in 1991 examined patient satisfaction and complications among 30,000 patients (80% survey return rate). The survey gathered data on the size (average: 15.1mm) and frequency (16.1%) of bruising and the number of attempts by phlebotomists per patient (1.03). Ninety-three percent of venipunctures were eventually successful (4.9% not attempted). But it doesn't state how many attempts were made before they were successful.
A CAP Q-Probe conducted in 1992 addressed the level of recollects at 70 hospitals: 95% were collected on first attempt; 2.8% required two attempts; 0.8% required three attempts and 1.1% required four or more sticks. Unfortunately, this data is a bit dated. We haven't seen any more recent studies published. I hope this helps.
Each month, PT--STAT! will publish one of the hundreds of phlebotomy FAQs in the growing database of questions and answers available in Phlebotomy Central, the members-only section of the Center for Phlebotomy Education's web site. For information on joining Phlebotomy Central, visit www.phlebotomy.com/PhlebotomyCentral.html.
Center to Release ABG Training Video
The Center for Phlebotomy Education will soon be releasing its latest addition to the popular Applied Phlebotomy video series. Work on Arterial Blood Gas Collections began in 2007 and is currently in the final editing phase. The Center hopes to make the DVD available by February. “As with all the Applied Phlebotomy videos, ABG Collections will reflect the current CLSI standard on arterial blood gas collection,” says Dennis J. Ernst MT(ASCP), the Center's director who is overseeing every aspect of production. “Because 90 percent of ABGs are drawn by respiratory therapists, the video also reflects the clinical practice guidelines for the procedure published by the American Association of Respiratory Care.”
The video, the first and only one of its kind on the market, demonstrates the step-by-step procedure for an arterial blood gas collection including performance of the Allen Test, acceptable sites for collection, arterial line draws, post-puncture care, complications of collection, and specimen labeling and transportation requirements. Interviews with authorities in the field as well as graphic animation depicting hematoma formation, arterial access, wrist anatomy, and needle-nerve contact make this video an exceptional training tool. The video was filmed exclusively at Clark Memorial Hospital in Jeffersonville, Indiana. Technical assistance and equipment were provided by Smiths Medical.
Denline Announces Survey Winner
Denline Uniforms recently announced the winner of the random drawing from those who participated in its recent online survey conducted with the cooperation of the Center for Phlebotomy Education, Inc.
The winner was Jill Johnson of Nebraska. Jill will receive a $500 gift card from Denline Uniforms. The survey asked respondents about their experiences with blood exposures during phlebotomy. The results will be published in a future issue of Phlebotomy Today-STAT!
Survey Says: Who's Drawing ABGs?
In this month's survey, phlebotomy.com asks visitors “Does your facility have a mechanism in place for monitoring the volume of blood drawn from newborns?” Sixty-seven percent admitted not having such a mechanism.
According to the Clinical and Laboratory Standards Institute, facilities should have some means to monitor the volume of blood drawn for pediatric and critically ill patients to prevent phlebotomy-induced anemia.
This month's survey question: After drawing blood into a syringe, do you use a safety transfer device to fill tubes? To participate in the survey, click here.
Center's Director Named to LabMedicine Review Board
Dennis J. Ernst MT(ASCP), editor of the Phlebotomy Today family of e-newsletters, has been recently appointed to LabMedicine's Editorial Review Board. LabMedicine, a peer-reviewed journal of the American Society for Clinical Pathology, is read by 70,000 members and subscribers worldwide.
"LabMedicine is proud to include Dennis Ernst on our board of esteemed subject matter experts,” says Bryan Nyary, LabMedicine's managing editor. “His expertise in specimen collection will further enable us to publish high quality articles for the laboratory community.”
Featured Product: CLSI Skin Puncture Standard
What Would You Do?
Each month, What Would You Do? presents a different case study, then asks readers to contribute their ideas as to how each situation would best be handled. The following month, selected responses will be chosen by the editor and published (sender will be identified by first name and state only). The most accurate, well written response will receive a free "Accurate Results Begin With Me!® t-shirt. The exercise will conclude with a review of the selected submissions and a discussion of the standards pertinent to the case study.
As a testimony to the caliber of PT-STAT! readers, everyone who responded got this one right. The unanimous answer: reject and recollect the specimen regardless of who drew it. There was very little patience among those who responded to the demands of a coworker to violate facility policy for a friend. According to Stella W., “If the RN is really a friend they would not ask you to break protocol which also says a lot about the type of RN they are.”
According to Susan H., this scenario occurs frequently: “This happens almost on a daily basis at our hospital, since ER draws all of their specimens….”
A typical response came from Mary K.:
“If this was an irretrievable specimen (such as a biopsy or bone marrow) then obviously it would be the responsibility of the nurse who was present during the collection to label it. If it was blood or urine, it should ABSOLUTELY be recollected. Any ethical nurse would understand, whether they were my friend or not. I would offer to contact the patient involved if the nurse felt uncomfortable. If it was my sample or a family member's I would much rather go to the trouble to have it recollected and would think more of the facility, not less, for being conscientious.”
Newt N. of Michigan didn't tolerate it when he sold life insurance, and he wouldn't tolerate it now: “Do what is right for the patient. Let me relay this story involving my former job as a life insurance salesman. A fellow agent (and good friend of mine) was required by our company to submit a urine specimen on an applicant in order to complete a life insurance policy. He peed in a bottle himself and sent it to the home office, whereupon the policy was approved and issued with a select status. I reported the incident, the policy was cancelled, and my friend lost a hefty commission check. I did the right thing.” Way to go, Newt.
Nearly all who responded spoke articulately and with firm resolve. We'd like to give them all awards. Since that's not possible, we randomly selected one lucky winner. Lana W. of New Zealand will receive a free Accurate Results Begin With Me™ ! t-shirt for her response:
“I would advise my colleague to recollect the specimen and explain to her that it would be dangerous and inappropriate to label an unlabeled specimen once it has been sent to the lab for testing. I also would advise her that she can't take the risk of labeling the specimen because she can't be 100% sure that this specimen is the one she collected from the patient since she did not label it at the bed side of the patient. I also would explain to her that I am not willing to accept her unlabeled specimen for all of the above reasons, and that I expect of her to understand my rejection as she has been trained to do the same if she was in my position. Therefore she should recollect the specimen. I also believe that friendship has nothing to do with this unfortunate situation.”
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