The Citrate aPTT is affected by poor technique References including blood collection and the transfer of Green RA, Thomas JS. Hemostatic Disorders: blood to the sample well. The accuracy of the Coagulopathies and . In Ettinger test is largely dependent upon the quality of the SJ, Feldman EC: Textbook of Veterinary blood specimen, which may be affected by: Internal Medicine, 4th ed. Philadelphia, Pa: WB • Foaming of the sample Saunders; 1995:1946–1963. ™ • Hemolysis of the sample IDEXX Coag Dx • Clotted or partially clotted blood Suggested Readings Evatt BL, Brogan D, Triplett DA, et al. Effect Citrate Activated Results greater than 300 seconds should of thromboplastin and analyzeration on the be considered abnormally high and the test. Clin Lab Haematol. Partial Thromboplastin Time (aPTT) test should be repeated or reported as 1981;3:331–342. >300 seconds. Gralnick HR, Kessler CM, Palmer R. The Package Insert Prothrombin Time: Variables Affecting Performance Characteristics Results. In: Triplett DA, ed. “Standardization of Reference range Assays: An Overview,’’ College of Citrated whole blood samples were obtained American Pathologists, Skokie, Il: 1982. from normal healthy animals and tested with Tseng LW, Hughes D, Giger U. Evaluation the Citrate aPTT assay. Reference ranges were of point-of-care coagulation analyzer developed as follows: for measurement of prothrombin time,

Species Canine Feline activated partial thromboplastin time, and in dogs. Am J Vet Res. 06-12914-01 Reference Range (sec) 72–102 65–119 2001;62:1455–1460.

Limitations Test results under 12 seconds and over 300 seconds are not reported. Instead, either an “Out of range - Lo” or “Out of range - Hi” Intended Use message is displayed. The Citrate aPTT is a unitized coagulation activating substance to standardize the test intended for in vitro use in performing activation of Factor XII, thereby providing a quantitative, one-stage Activated Partial a more precise and sensitive assay. The Thromboplastin Time (aPTT). The Citrate addition of a contact activator such as glass, aPTT test is performed using citrated canine kaolin or diatomaceous earth distinguishes the or feline whole blood. This test is to be aPTT from the PTT. used in the Coag Dx™ Analyzer and is also The Citrate aPTT assay resolution is achieved compatible with the SCA2000™ Coagulation through the use of a factor 3 substitute Analyzer. and a kaolin activator, and does not require This test is for veterinary use only and not an incubation step. Since little specimen for human diagnostic use. processing is required, Citrate aPTT results are obtained in less than four minutes. In addition, because the test is performed using Summary and Explanation a citrated whole blood sample, testing can The Citrate aPTT is a measure of the intrinsic be performed for up to 2 hours after sample and common coagulation pathways, which collection without affecting test results. involves all coagulation factors except Factors VII and III (tissue factor). The aPTT is a modification of the Partial Thromboplastin Principle of Operation Time (PTT). The PTT uses a phospholipid The coagulation analyzer utilizes a mechanical © 2007 IDEXX Laboratories, Inc. All rights reserved. derived from either brain or lung tissue to end point clotting mechanism in which clot Coag Dx is a trademark or registered trademark of IDEXX Laboratories, One IDEXX Drive mimic the role of in the coagulation formation occurs within the disposable Citrate Inc. in the United States and/or other countries. SCA2000 is a trademark of Westbrook, Maine 04092 Symbiotics, Inc. idexx.com process. The aPTT contains a contact aPTT cartridge. Following citrated whole

1 blood sample introduction, the analyzer the marked expiration date. Redating is Syringe sample, from indwelling line or The analyzer emits an audible tone when it precisely measures 15 microliters of blood necessary if stored at room temperature. venipuncture is ready and alternately displays the “Add and automatically moves it into the test Mark the outer box with the new expiration Note: The amount of blood required to Sample” and “Press Start” messages. The channel within the Citrate aPTT cartridge. The date when cartridges are stored at room adequately flush the line until it is free of analyzer remains in the “Ready” mode remainder of the blood sample, not needed temperature. contaminants is dependent on the amount for 5 minutes before a “START... timeout” for testing, is automatically drawn into the of solution contained within the line. Greater message displays. If this occurs, a new test waste channel of the cartridge. Sample/ volumes will be required to clear longer lines. cartridge must be placed in the analyzer. reagent mixing and test initiation are also Sample Collection 1. Collect a sufficient sample to fill the blood 3. Citrated samples should be collected prior performed automatically, requiring no operator Blood samples to be used for coagulation collection tube. to start of test. (See the Sample Collection interaction. After mixing with the reagent, the testing must be collected in the following section for more information.) sample is moved back and forth within the test manner to prevent contamination with tissue 2. Attach a needle to the syringe. Carefully channel and observed for clot formation. thromboplastin, or indwelling intravenous (I.V.) puncture the stopper of an evacuated test 4. Before testing, invert the test tube at least solutions that interfere with the coagulation tube containing sodium citrate (3.2%) and four times to ensure complete mixing of The clot detection mechanism consists of a assays. Poorly collected blood samples with allow blood to be drawn into the tube until the sample. series of LED optical detectors aligned with visible clotting or debris accumulation must be the flow stops. 5. Remove the stopper. Then, using a syringe the test channel of the cartridge. The speed discarded and a fresh sample collected. at which the blood sample moves between 3. Mix gently. Discard the syringe with the or a pipette, transfer one drop of citrated the detectors is measured. As clot formation Patient excitement should be minimized needle. blood into the center sample well of the begins, blood flow is impeded and the as this can increase platelet count, platelet test cartridge; fill from the bottom of the movement slows. The analyzer recognizes that aggregation, and the levels of von Willebrand well up. A sufficient quantity of blood must the clot end point has been achieved when the Factor (vWF), , and Factors V and Operating Instructions be added directly to the center sample well movement decreases below a predetermined VIII. Prolonged venous stasis and excessive Before performing any assay, refer to the to fill it flush to the top. Should a large drop rate. The Citrate aPTT whole blood clotting probing for the vessel should be avoided. IDEXX Coag Dx™ Analyzer Operator’s Manual of blood extend above the center sample time is reported in whole seconds. Use of the cephalic or saphenous veins are for detailed operating instructions. well, push it over into the outer sample well. advised as bleeding is easier to control from Material provided 6. Press the Start key. A single beep these sites (Green, et al, 1995). If a syringe signals the start of the test. The analyzer Reagents is used, it should have a 23-gauge needle or • Citrate aPTT test cartridges automatically mixes the sample with the Each box of Citrate aPTT test cartridges larger. Use of excessive force when expelling • 11 single-use disposable pipettes reagent and detects clot. contains: the blood specimen through the needle may Material required (not provided) cause hemolysis. 7. The analyzer emits a single beep when the • 10 pouches, each containing one Citrate • Coagulation analyzer test is complete. aPTT test cartridge and one dessicant Note: It is recommended that coagulation testing be performed within two hours • Evacuated tube containing The test result, in seconds for whole The Citrate aPTT test cartridge is a self- of sample collection if stored at room sodium citrate (3.2%) blood, remains on the screen until the test contained disposable test chamber temperature. cartridge is removed from the analyzer and preloaded with a dried preparation of kaolin, • Blood collection needle for 120 seconds following its removal. phospholipid, calcium salts, stabilizers Note: Blood samples for testing should be Note: Citrate aPTT test cartridges must be and buffers. Each cartridge is individually collected at least 5 minutes prior to testing to at room temperature prior to use. Once packaged in a pouch. Cartridge pouches are allow for adequate mixing of the sodium citrate removed from the refrigerator, this may Operating Precautions stamped with a lot-specific expiration date. with the sample. take up to 60 minutes. For best results, Do NOT use cartridges that are past their Caution: All used test cartridges should be the pouch should be opened immediately marked expiration date, or that have been Citrated sample, from a direct considered as potentially infectious, handled prior to testing. improperly stored. venipuncture with care and disposed of properly. 1. Prepare the venipuncture site by cleansing Test procedure Do NOT force a cartridge into the analyzer. with alcohol and allowing to air-dry Refer to the IDEXX Coag Dx™ Analyzer If resistance to insertion is encountered, Storage and Stability completely. Operator’s Manual if any fault message should gently remove the cartridge and examine the cartridge slot. Remove any obstruction before When refrigerated (2°–8°C), the foil-pouched appear during this procedure. 2. Collect a blood sample directly into an attempting further use of the analyzer. Citrate aPTT cartridges are stable until the evacuated test tube containing sodium 1. Insert a test cartridge into the cartridge marked expiration date. Room temperature citrate (3.2%) and allow the blood to be opening of the analyzer. The cartridge must Specimen collection and handling for all storage (15°–30°C) is optional for unopened, drawn into tube until the flow stops. be inserted with the blood reservoir facing coagulation testing requires careful adherence pouched cartridges. Citrate aPTT cartridges to guidelines. As with all diagnostic tests, test 3. Mix gently. up. The analyzer will automatically identify should not be exposed to temperatures in the test cartridge and display the test type. results should be scrutinized in light of a specific excess of 37°C. patient’s condition and anticoagulant therapy. 2. During the warming stage, observe the Any results exhibiting inconsistency with the Note: Room temperature redating is to a display for fault messages. patient’s clinical status should be repeated or maximum of 4 weeks, but must never exceed supplemented with additional test data.

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