centrifugation at approximately 2000 g for 15 minutes
yields PFP (platelet free plasma). The ‘g’ is a function of
length of rotor head and RPM. It is for this reason each
laboratory must calibrate its own equipment to achieve
satisfactory samples depending on test performed and
kind of plasma sample required.
(Courtesy: Tulip Group of Companies)
Ready to use 3.2% buffered citrate solution for coagulation
assays and ESR by Westergren method.
Accurate coagulation testing is dependent on numerous
preanalytical variables, which may affect the results of
routine coagulation assays. To improve the precision and
accuracy of laboratory testing, it is important to identify
these variables and control their potential effect on results.
Preanalytical variables pertinent to routine coagulation
testing can be classified into three major categories:
specimen collection, specimen processing and specimen
storage and transport. 3.2% citrate is also the anticoagulant
of choice for performing ESR by Westergren method.
Laboratory reagent: Ready-to-use solution.
Profact is a unique ready-to-use 3.2% buffered trisodium
citrate solution formulated for collection of blood for
routine coagulation assays. Profact can be used for sample
preparation in the following clot based assays such as PT,
APTT, TT, quantitative estimation of fibrinogen, test for
factor deficiency, test for lupus anticoagulants, protein C
and protein S tests. Profact can also be used for collection
of blood to perform ESR by Westergren method.
About 3.2% trisodium citrate is the anticoagulant of choice
for coagulation studies. When anticoagulated blood is
centrifuged for preparing PPP for routine coagulation
assays, the centrifugation process leads to release of
carbon dioxide (CO2). The end result being shift in pH,
which has an adverse impact on the results of clot-based
assays. Profact incorporates 3.2% trisodium citrate in a
unique protective solution, which arrests shift in pH due
to the release of carbon dioxide during centrifugation. Also
labile factor V and VIII are well preserved and the results of
clotbased assays are more accurate.
Also Profact incorporating 3.2% citrate is the anticoagulant of choice for ESR by Westergren method.
¾ Store the reagent at 2 to 8°C
¾ Stability of unopened vial: 12 months from the date of
¾ Stability of opened vial: 90 days from the date of
opening, provided it is not contaminated.
Material Required But Not Provided
Sterile and clean 0.5/1 mL micropipettes, micropipette
tips or glass blow out pipettes, ESR tube.
Sample Collection and Preparation
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 provides sample with a desirable
Withdraw blood without undue venous or frothing into
a plastic syringe fitted with a short needle of 19 to 20 SWG.
The venipuncture must be a ‘clean’ one and if there is any
difficulty, take a new syringe and try another vein. Transfer
the blood into tubes containing Profact, after detaching the
needle from the syringe. Do not delay mixing blood with
Profact. Avoid foam formation during mixing. Mix exactly
nine parts of freshly collected blood with one part of
Profact. 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 to 3000 rpm (approximately 1500 g) on a
laboratory centrifuge and transfer the plasma into a clean
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 is 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 3 hours. Also
plasma samples obtained after collection with Profact
may be stored at –20°C for 2 to 3 weeks before testing.
For performing the test, venous blood is mixed accurately
in the proportion of 1 part of Profact and 4 parts of whole
The sedimentation rate is reduced in stored blood,
hence, the test should be carried out within 4 hours
of collecting the blood, and a delay up to 6 hours is
permissible provided that the blood is kept at 4°C.
1. Take every possible aseptic precaution to minimize
contamination while drawing the reagent.
Clinical Hematology: Bleeding Disorders 281
2. Avoid dipping contaminated pipettes/micropipette
tips in the reagent vial. Ideally pour the required
quantity for the day's work into another sterile clean
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