Blending studies test a patient’s blood to determine if they have a clotting factor deficiency or inhibitor. Donor plasma is mixed with the patient’s plasma to see if it clots normally. False results can occur, and further testing may be needed for a specific diagnosis.
Blending studies are used to determine the cause of slow clotting in a patient who is not taking blood thinners or other medications that could interfere with the clotting processes. A sample of the patient’s blood can be tested in a laboratory to determine whether the problem is a deficiency of a clotting factor or a clotting inhibitor that is making it difficult for the factors to work properly. The results may provide more information on how to proceed with diagnostic tests and possible treatment of the problem. Medical providers may recommend mixing studies for patients who have unexplained recurrent bleeding, slow clotting, and related problems.
In this test, the technician separates the blood plasma and makes sure that it is processed very well so that it is as pure as possible. The patient’s plasma is mixed with a sample of healthy plasma with a known concentration of clotting factors and monitored. Technicians measure prothrombin time (PT) or partial thromboplastin time (PTT) or both during mixing studies, looking at how long it takes for the treated mixture to clot.
If the sample clots normally, this indicates that the patient has a clotting factor deficiency. Donor plasma provides enough clotting factors to mix studies to help blood clot as it would under normal conditions. Further tests can determine precisely which blood components are involved. This information can help doctors arrive at a diagnosis and determine how to treat the patient.
A clotting failure usually means that the patient’s plasma contains inhibitors that act against clotting factors to prevent clotting. A note of caution is needed when monitoring inhibitors in mixing studies, as sometimes a sample will appear to clot normally, but then slow down thereafter. This occurs when inhibitors take some time to fully activate. Technicians will recheck a sample that appears to be behaving normally to confirm that it is following the clotting cascade, indicating a problem with a clotting factor rather than an inhibitor. If the clotting behavior changes, this is the result of an inhibitor.
False test results can occur in some cases, and patients may need to send in a second sample to allow a lab to double check the results, especially if they are unexpected. Samples may also be evaluated for more specific inhibitors and clotting factors once the cause of the patient’s bleeding disorder is more evident. Advanced tests can be more expensive, which is why doctors are reluctant to recommend them until they seem warranted.
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