by Donna Castellone, MS, MT (ASCP) SH •
January 21, 2022
The interpretations below are provided by Donna Castellone, MS, MT (ASCP) SH for Aniara Diagnostica.
Welcome to 2022! A new year, and hopefully a new beginning to a better year, more health, less COVID, more freedom.
One thing is for certain, laboratories have been doing more with less for a long time, but never more than in the past two years. Between staffing shortages and people out due to COVID and quarantine protocols and baby boomers retiring, automation is extremely important. Using point of care testing has become critical in providing rapid test results. Streamlining processes are important but providing quality results are still of the utmost importance. What about some of the more labor-intensive manual tests? They can provide insights into a patient's coagulation profile, but if you don’t have the staff, or if the information they provide is minimal at best should they continue to be performed? It is also important to note that many of these tests may be considered laboratory developed tests (LDTs) and laboratories must adhere to the proper regulations.
Manual PT or aPTT:
It is important to understand what a clot looks like so it is beneficial to know how to perform a tilt tube. This is not something to be used for when an analyzer goes down, but can be used to confirm when a clot isn't detected, or if there is a short clot that occurs prior to a lamp reading (if your analyzer uses optical detection). If you do use this for that purpose, make sure that your techs are competency assessed on this procedure, and you have some type biannual proficiency testing. It is not something that I would keep on a test menu, but it is not a bad thing to have staff know how to perform, for a just in case point of reference.
Euglobulin Clot Lysis:
This test measures overall fibrinolysis. Citrated platelet poor plasma is mixed with acid in a glass test tube. The acid causes precipitation of clotting factors including fibrinogen, PAI-1, tissue plasminogen activator (tPA), plasminogen and a small amount of alpha 2-antiplasmin, as well as factor VIII. The tube is centrifuged and the supernatant is discarded. The participant is dissolved in a buffer and clotted with thrombin. The time to clot lysis is inspected every 15 minutes. It is important to compare the patient to a normal plasma.(1)
Increased fibrinolysis which would result in a decreased ECL occur in FXIII deficiency, thrombolytic therapy, or following DDAVP therapy. Decreased fibrinolysis, or an increased ECL occurs in pregnancy, DIC, liver transplant and recurrent VTE.(1)
Based on the time-consuming nature of this test, and the non-specific information from this test, this may be a test that doesn’t need to be performed and information can be provided by more specific testing.
Factor XIII Screen:
Factor XIII or fibrin stabilizing factor is the last step of the clotting cascade. When mutations of the F13A1 or the F13b gene result in the deficient levels of functional factor XIII causing blood clots to be weak and unstable resulting in breakdowns of clots. It also plays a role in proper wound healing, carrying pregnancy to full term and the development of new blood vessels.(2) Symptoms occur at any age but most often occur at infancy including epistaxis, bleeding from gums, ecchymoses, hematomas, easy bruising, menorrhagia and bleeding into soft tissues and around the joints. Bleeding after trauma or surgery is delayed and develops within 12-36 hours. It has also been associated with recurrent miscarriages.(2)
A clot solubility tests may be used to aid in the diagnosis of Factor XIII deficiency. It uses either 1% of monochloracetic acid or 5m urea. However, it is only abnormal in patients with individuals with less than 1% of FXIII. So patients with low levels will have a normal screen test. This deficiency will not be detected by the PT or the aPTT, they will be normal in a FXIII deficient patient. So, this test will only be abnormal in severely deficient patients. The test also must be read after 1 hour and after 24 hours. The clot will be present at one hour and may be gone after 24 hours. There also has to be sufficient fibrinogen for the test to work, and it may be abnormal in pediatric patients, due to "flimsy" fibrinogen. It is important to run the test with a normal patient to ensure the accuracy of your reagents. There is no negative control. So is this a good test to keep? To really diagnosis a FXIII patient, you would have a positive family bleeding history, a normal screening test, and most likely the best test would a proper FACTOR XIII chromogenic or antigen level.
Keeping a FXIII screening test on your test menu means you have to continue some type of biannual proficiency test and also competency assessment for your staff. Not sure this test provides the information that the upkeep requires.
Measuring thrombolytic activity is important in determining the effectiveness of thrombolytic agents in MI and stroke. The spectrophotometric analysis of thrombolytic activity (SATA) is standardized by using tissue plasminogen activator (tPA) to measure in vitro thrombolytic activity. The analysis is designed to measure clot lysis by using a PTT reagent with calcium chloride to form a clot. It is based on the UV absorbance of hemoglobin of red blood cells released from a clot. The optical density of the dilutions of the lysed clot of 405nm. This is the wavelength which is the peak absorption of hemoglobin and detect the RBCs that are released from the clot as thrombolysis continues.
This can be used to estimate and compare thrombolytic activities and to compare the concentration of tPA, streptokinase and urokinase.
This test appears to be a cost effective method in which to be able to determine concentrate of thrombolytic agents. It may be something that might be implemented in a stroke center. Thrombolytics have a very short half life, and most patients do not have blood drawn due to the risk of bleeding, but there may be a need for this type of testing either during a clinical trial or in some clinical situations.
Most testing in the laboratory is guided by your patient population, and the needs of your clinicians. Having good communication among the directors, hematologists and pathologists, while keeping in mind what provides the best information for your patients is important. It is also important as laboratorians to advocate for your testing and what you can safely and accurately provide to your patients. Because some tests can be performed, doesn't mean they should be performed. The more that you can standardize a test, use purchased reagents, manufactures controls and minimize variables the better the outcomes.