For this week, I was attached to the Special Cogaulation Lab where there are many SPECIAL tests carried out. These tests require reagents that are expensive thus I do not really have any hands-on. All I can do is just observed. Some tests done in the lab are automated while some are done manually. For those tests done manually, timing is very important as reactions take place constantly.
For this entry, I shall share with all of you about the soluble fibrin monomer complexes test which is done manually in the lab.
Soluble fibrin monomer complexes test
USE:
It is a rapid qualitative test for the presence of the monomer in the plasma by the hemagglutination technique.
PRINCIPLE:
Fibrin monomers are intermediate products between fibrinogen and fibrin. They are produced during the proteolysis of fibrinogen by thrombin. [Proteolysis: digestion of proteins by enzymes called proteases] When the thrombin concentration in plasma is low, fibrin monomers are in insufficient quantities to aggregate to form a fibrin clot. Thus, fibrin monomers associate themselves with fibrinogen/ with fibrinogen degradation products to form soluble complexes. The presence of small amounts of soluble fibrin monomer complexes in the plasma can quickly be visualized with the F.S test by the agglutination reaction of human erythrocytes coated with purified fibrin monomer which do not agglutinate with normal plasma.
TYPE OF SAMPLE: Blood in sodium citrate tube.
PROCEDURE:
1) 100mL of patient’s plasma, 100mL of positive control and 100mL of negative control are added to 3 separate tubes.
2) 50mL of F.S test reagent is added to each tube and mixed well.
3) The tubes are incubated for 10 minutes in the water bath.
4) The tubes are removed from the water bath and dried. The contents in the 3 tubes are transferred using a pipette to a circle on the hemagglutination plate.
5) The plate is rocked gently to make the liquid swirl around the circle for 6 minutes.
6) The hemagglutination patterns of the patient’s plasma are then compared with those of the negative and positive controls.
REFERENCE RANGE:
Normal plasma does not produce agglutination of the F.S test.
INTERPRETATION:
Positive F.S test may be found in the following clinical conditions:
-Liver disease/cirrhosis
-Angioma
-Leukemic cancer
-Infection/Septicemia
-Polytraumatic condition
-Obsteric complications
-State of shock
-Thrombotic disease
-DIC of other organs
DONE BY:
Malerie Goh
TG02
Subscribe to:
Post Comments (Atom)
16 comments:
Hey Malerie!
Is this a common test done for the samples that your lab receives? Or are there other similar tests that can be done to determine if the patient's coagulation system is functioning properly?
And, why must the blood be collected in sodium citrate tube and not EDTA or Heparin?
Thanks!
Yvonne Teo
Hi! =)
You mentioned that 'For those tests done manually, timing is very important as reactions take place constantly.'Can i know what are some of the reactions that take place constantly?
And what is F.S test?
Thanks.
Lyn
TG02
Hi,
U mentioned that the liquid swirl around the circle for 6 minutes in one of the steps.
I would like to know what does the liquid refers to? and what is the principle behind this step.
Thanks alot =)
Zhenling
TG02
hi malerie, i was just wondering, does your lab do the Lupus anticoagulant test too? because my special coag lab does it. I was wondering if its done the same method as my lab. Maybe you could briefly describe a bit of that test to me?
-cornelyus
Hi Yvonne,
Well, there are certainly many tests to test if the patient’s coagulation system is functioning properly such as factor assays which can determine the activity of extrinsic and intrinsic coagulation factors present in the human plasma.
Sodium citrate tubes are used instead of EDTA as coagulation testing requires the tubes to be 90% filled. Only sodium citrate tubes are manufactured in a way that allows the tube to be 90% filled due to its evacuated system, where blood is able to flow into the tube until it stops automatically.
Heparin tubes are not used as there are certain tests done in the Special Coagulation lab is to test for heparin and in certain tests such as the Lupus Anticoagulant test; heparin is seen as a contaminant as it will interfere with the results, giving rise to false positive results.
Malerie
Hi Lyn,
An example of reactions that take place constantly is the anti-Xa method for heparin. Factor Xa is inhibited by antithrombin-heparin complexes. To test for the presence of these complexes, factor Xa is added and incubated for 30seconds. Factor Xa will react with anti-Xa that is present in the patient’s plasma. A substrate is then added to produce a colour and incubated for another 30seconds. Acetic acid is immediately added to stop the reaction, or else the colour will get darker and this will affect the reading when measured using the spectrophotometer.
Opps. Sorry forgot to include that F.S test is the name of the test that uses the hemagglutination technique to test for the presence of soluble fibrin monomer complexes. Hope I’ve cleared your doubts =)
Malerie
Hi zhenling,
The liquid refers to the contents in the 3 separate tubes, which are mixed with the F.S test reagent– the positive control, the negative control and the patient’s plasma. By making the liquid swirl, it will help in the agglutination reaction if there is any soluble fibrin monomer complexes present in the plasma.
Malerie
Hi Malerie,
1(a)I am curious to know why is soluble fibrin monomer complexes test considered a special test? What do you meant by special?
(b)The procedures to the test is relatively easy from what you have described. Besides the concern of the cost of reagents and time, what other concerns are there which prevent you from doing the test?
2)If a patient is found positive for the test, are there any confirmatory tests?
3(a)Could you kindly explain what is angioma, polytraumatic condition and obsteric complications?
(b)What possible signs and symptoms will patient suffering from the above show?
5)Why is soluble fibrin monomer complexes test considered a qualitative test but not quantitative test?
Thankz alot!
Han Yang
TG01
Hi:) can i ask what other tests your lab does?can give me some names of the tests?thanks:)
Rachael
Tg01
0606168C
hi corneylus,
for LA there are 2 screening tests and 1 confirmatory test to be done. the 2 screening tests are PTT-LA and DRVVT (Dilute Russell's Viper Venom Test). DRVVT consists of LA-S(Screen) and LA-C(Confirm). a confirmatory test, platelet neutralisation test is done. it consists of R1 and R2. if 2 out of 2 of the tests above are positive, LA is demonstrated.
Malerie
hi rachael,
other tests include LA (Lupus anticoagulant), Protein C, Protein S, Fibrinogen assay. D-Dimer, antithrombin III, factor assays, etc.
Malerie
To Han yang
1)(a) soluble fibrin monomer complexes test is considered a ‘special’ test as the test is not done by the routine coagulation test. Although the samples are received by the routine lab, the special coagulation lab will perform/carry out the test.
(b) besides the cost of reagents and time, another concern is experience of the med tech. the staff carrying out the various tests which only the special coag lab does are all senior med techs or hav been working there for more than 20 to 30yrs or so.
2) there are no confirmatory tests. Soluble fibrin monomer complexes test is just one of the tests done to test for DIC. Soluble fibrin monomer complexes test is usually not ordered individually. It is usually ordered together with fibrinogen assay and/or d-dimer, depending on the doctor.
3)(a) angioma are tumors that are benign. polytraumatic condition is when the patient is suffering from many severe injuries. For obsteric complications, there’s a typo. It’s obstetric, complications that arise in a woman and her child during pregnancy, childbirth and shortly after birth.
4) it is a qualitative test as the test depends on whether there is agglutination or not to determine if soluble fibrin monomer is present or not. There are no numerical results involved like in ESR. ESR is a quantitative test.
Malerie
hi malarie..
i was just wondering..what is the purpose of incubating the tubes in a water bath for 10 mins? can the tubes be incubated at normal room temperature?
Nur Azeimah
0607060A
TG02
hi azeimah,
the tubes are incubated for 10mins to allow the patient's plasma, positive control and negative control to react with the F.S test reagent so that haemagglutination can happen when the samples are placed on the haemagglutination plate.
as the tubes are mixed with the F.S test reagent, they should be incubated in the water bath. like PT and PTT reagents, F.S reagent should be incubated in the water bath. though i'm not sure why, but that's the requirement :)
Malerie
I have 2 comments to your answers.
1. Are your sure the only reason for the use of sodium citrate tube instead of EDTA or Heparin is due to the ability of vaccum in the tube to fill 90% of the tube? Why fill 90% for sodium citrate? Please read up more before you provide answers to your friends. You will confuse them if your asnwers are not clear.
2. Why the incubation has to take place in the water-bath? You did not answer the question. You need to go and find out what is the temperature of the water-bath. You cannot just answer to say is the test requirement. There must be a reason for this step in the protocol.
You need to improve your way of learning. Learning is not passive but active. you must find out more or read up more to understand the principle of performing test in clinical laboratory. Every step in a protocol has their reasons.
with regards to ms chew's comments, i've decided to rephrase my answers to yvonne's 2nd question and azeimah's question.
1. another reason for using the sodium citrate tubes is due to its mild calcium-chelating properties which makes it more suitable for coagulation assays. EDTA is a potent calcium-chelator thus it may falsely lengthen clotting times with calcium-dependent coag tests.
for sodium citrate tubes, it needs to be 90% filled as the dilution requirement ratio of blood:anticoagulant is 9:1. if it is underfilled, the sample is rejected as it may lead to false results.
2. for this Q, ms chew, i was told it is a test requirement. anyway, i asked the more senior staff there. he also said that since the maunfacturer state must do this so they just follow but he THINKS that it must be incubated in the water bath which is 37 degrees celsius(body temp) may be due to the fact that these reactions take place in the human body so incubating it in the water bath and not at rm temp which is 22 degrees celsius will play a part in the reaction.
hope my answers are clearer now.
Malerie
Post a Comment