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Learning CenterCoagulation CornerThursday, February 2, 2012
COAGULATION CORNER: FEBRUARY 2012Medical Errors in the Coagulation LaboratoryMedical errors are still one of the most frequent causes of patient death. An adverse event is defined as any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medical treatment or procedure, regardless of whether it is considered related to the medical treatment or procedure. Most common in coagulation would be excessive bleeding due to the administration of anticoagulants. The study, by researchers from the US Centers for Disease Control and Prevention (CDC), singles out 4 drugs and drug classes as being the most common causes of adverse events: warfarin, oral antiplatelet medications, insulins, and oral hypoglycemic agents. Alone or together, they account for 67% of emergency ADE hospitalizations of adults 65 years and older. Warfarin was implicated in 33%! In contrast, medications red-flagged as high risk or inappropriate by health authorities explained only 1.2% and 6.6%, respectively, of such hospital admissions. Two-thirds of the emergency hospitalizations were due to four medications, either used alone or in combination:
For clinicians, the take-home message of the study is clear: Improved management of antithrombotic and antidiabetes drugs can keep thousands of seniors out of the hospital. So with all of the events that occur due to drugs, how scary is it that 2 coagulation drugs: Anti-platelet drugs and an anticoagulant –warfarin, are responsible for most events! And how does the laboratory help to prevent errors: Errors in the Coagulation Laboratory: THE ISI and the INR: Okay so we know that warfarin is one of the most dangerous drugs. It is imperative that we ensure in the laboratory that our PT reagents have the correct ISI to reflect the correct INR. Check your analyzers, to ensure the correct ISI provided by the manufacturer is enterd and part of the calculation. Also, using calibrated standardized plasmas can help to harmonize your ISI among analyzers. If your INR is incorrect, you can impact a patients dose of warfarin, causing them to either be over or under anticoagulated and putting them at risk. Insensitive reagents: It is important to understand how your reagents work and that they correctly reflect a low level of factor activity. A PT and or APTT should be prolonged when levels of factors approach 30%. This is the level in which a patient may bleed. If a reagent is insensitive to a factor, the screening test may be normal and may fail to detect a patient who may bleed. Adding an APTT on to a sample > 4 hours old: An APTT is stable for 4 hours (CLSI guidelines). An APTT on a patient that is receiving heparin should be performed within 2 hours. If an APTT is added onto a sample that is older than 4 hours old, PF4 will neutralize the heparin in the sample, falsely decreasing the APTT. This can cause a clinician to increase heparin in a patient, putting them at a risk for bleeding. LMWH and the APTT: You cannot monitor levels of LMWH with the APTT, however, LMWH can prolong the APTT (at levels of about 0.6U/ml). This prolongation is a result of the LMWH and is not due to a factor deficiency. It is important for laboratories and clinicians to understand this may occur so as not to needlessly expose a patient to product. New anticoagulants: The new direct thrombin inhibitors perform very well, and inhibit the formation of thrombin. However, when patients are on this, all clot based assays will be prolonged, and factor assays will demonstrate the presence of an inhibitor. Additionally, since there are no FDA approved tests for monitoring these drugs, there is no way to determine if a patient is properly anticoagulated. Anti-platelet drugs: An issue with anti-platelet drugs is that many patients have genetic mutations that impact the drug metabolism. As a result, dosing patients is challenging. Many clinicians exceed the recommended dose to eliminate any issues with patients demonstrating resistance to these drugs. However, this puts a patient at a bleeding risk. Additionally, clinicians question if these drugs need to be monitored, since there really isn’t a gold standard method. Recombinant FVIIa: Giving activated factor VII is a very effective way to stop bleeding. Conversely, it can also cause a patient to have a thrombotic event. It is important that laboratories are aware, that patients on this drug will present with a shortened PT, which may present itself as an undetectable clot in an optical system, when in actuality the clot formed prior to the lamp reading. This can result in reporting out a prolonged result, when in reality it is a very shortened PT. So, as you can see there are many issues in the coagulation laboratory that can cause errors in patient results- Let us not forget the issues that may also occur that we don’t even know about:
Yikes, sometimes too much information isn’t best! So, put your best foot forward when performing coagulation testing, and try to remember, you aren’t testing an ID number, it is someone’s mother, father, sister or brother. Also, techs have really good instincts; I would rather go the extra mile and investigate, then just give a number. Remember we promise to “do no harm”! Donna Castellone
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