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  5. Avoid exposure of the Uniplastin reagent to elevated temperatures, contamination and undue stress due to high and low temperature exposure cycles. Immediately replace reagent cap after use and store at recommended temperatures only. 6. On prolonged storage at 2–8°C, the thromboplastin suspension has a tendency to settle down. Homogenize the reagent by resuspending before use. Additional Material Required 12 × 75 mm test tubes (plastic tubes are preferred), 0.1 mL and 0.2 mL precision pipettes, stopwatch, water bath or heating block at 37°C, fresh normal plasmas for establishing MNPT. Sample Collection and Preparation of PPP Though no special preparation of the patient is required prior to sample collection by approved techniques, it is preferable that patients are not heavily exercised before blood collection. Fasting or only light non-fatty meals prior to blood collection provide samples with a desirable lower opacity. Withdraw blood without undue venous stasis or frothing into a

  5. Avoid exposure of the Uniplastin reagent to elevated temperatures, contamination and undue stress due to high and low temperature exposure cycles. Immediately replace reagent cap after use and store at recommended temperatures only. 6. On prolonged storage at 2–8°C, the thromboplastin suspension has a tendency to settle down. Homogenize the reagent by resuspending before use. Additional Material Required 12 × 75 mm test tubes (plastic tubes are preferred), 0.1 mL and 0.2 mL precision pipettes, stopwatch, water bath or heating block at 37°C, fresh normal plasmas for establishing MNPT. Sample Collection and Preparation of PPP Though no special preparation of the patient is required prior to sample collection by approved techniques, it is preferable that patients are not heavily exercised before blood collection. Fasting or only light non-fatty meals prior to blood collection provide samples with a desirable lower opacity. Withdraw blood without undue venous stasis or frothing into a

  if there is any difficulty, take a new syringe and needle and try another vein. Transfer the blood into anticoagulated tubes, after detaching the needle from the syringe. Do not delay mixing blood with anticoagulant. Avoid foam formation during mixing. Mix exactly nine parts of freshly collected blood with one part of trisodium citrate (0.11 mol/L, 3.2%) or Profact available from Tulip; For occasional patients with hematocrit less than 20% or greater than 50%, this ratio must be readjusted to ensure valid results. Centrifuge immediately for 15 minutes at 1500-3000 rpm (approximately 1500 g) on a laboratory centrifuge and transfer the plasma into a dean test tube. It should be ensured that the plasma is free from platelets (PPP). Cap the test tubes to prevent deterioration of samples. Plasma must be tested preferably immediately. However if the specimen are held at 22 to 24°C then they may be tested within 2 hours and if the specimen is held at 2 to 4°C then they may be tested within

  A PT ratio is obtained by dividing the patient PT in seconds by the “Mean of the normal range” (MNPT). This ratio is then “normalized” by raising the results to the power of the ISI of the PT reagent used. If “normal control plasmas” are used in place of patient plasma for arriving at the MNPT it can affect the evaluation of the patients level of anti-coagulation. Clinical Hematology: Bleeding Disorders 283 For example: Reagent ISI=2.5 Test Day 1 Test Day 2 Test Day 3 Patient PT (sec) Normal Control (10.4-12.3 sec) INR Formula [R]’SI Resulting INR 16.0 11.5 16.02.5 11.5 2.27 16.0 10.4 16.02.5 10.4 2.89 16.0 12.3 16.02.5 12.3 1.92 If the control time is greater than the mean normal range (MNPT), the PT ratio for any patient, PT will be smaller, potentially leading to over coagulation. If the control time is lesser than MNPT the ratio for any patient PT will be greater, leading to under coagulation. On the other hand, MNPT for a particular laboratory using the same combination of metho

  each laboratory must calibrate the necessary force and time required during centrifugation to yield PPP. 2. Incorrect mixture of blood and Profact is a potential source of error both in coagulation assays and ESR estimation. 3. If the reagent vial develops turbidity, do not use the reagent as this would lead to erroneous results. Calibration of Instruments/Equipments ¾ Water baths or heating blocks calibrated and preset at 37 + 0.5°C are an important requirement to achieve accuracy and reproducibility. • The whole process of the coagulation tests is based on a series of enzymatic reactions, which are dependent on pH, ionic strength and the temperature of the reaction process. A correct temperature at 37 + 0.5°C is critical as most of the reagent systems are standardized at this temperature. Day-to-day shift in reaction temperature of equipment will introduce uncontrolled variation into test conditions. Therefore, temperature of all equipments must be calibrated daily and diligentl