Hello everyone! I've been attached to the haematology department for the past 7 weeks. There is 1 test that I'll like to share with you'll.
D-dimer Test (coagulation test)
The specific degradation of fibrin(i.e. fibrinolysis) is the mechanism responding to fibrin formation. Plasmin is the fibrinolytic enzyme that degrades fibrin into D-dimer. Hence, its appearance in the plama indicates that the fibrinolytic system is working in response to coagulation activation.
Coagulation Activation Plasmin
Fibrinogen -------------->Fibrin------------>D-dimer
D-dimers are crossed-linked degradation products of fibrin. D-Dimers are often associated with deep venous thrombosis(DVT), disseminated intravascular coagulation(DIC) and embolisms.
Hence, D-dimer can serve as a screening test for DVT.
Test Principle
D-Dimer test is a rapid latex agglutionation slide test that uses mouse monoclonal antibodies for semi-quantitative determination of D-dimer in the human plasma. The latex particles in the D-dimer reagent are coated with mouse anti-human D-dimer monoclonal antibodies. If the patient's plasma contains D-Dimes, it will cause agglutination when mixed with the latex particle suspension.
Test Procedure
1) The patient's plasma sample is checked against the name on the lab test request form.
-Neat Report-
2) 20uL of patient's plasma is pipetted into 1 circle on the black test card.
3) 20uL of D-dimer reagent is pipetted into the same circle on the test card.
4) The 2 drops on the test card are mixed using a mixing rod.
5) The test card is manually rotated for 2 mins in a manner such that the liquid swirls around the entire test circle.
6) When 2 min is up, check for agglutioination (i.e.bluish-white dots).
7) If no agglutination is observed, it is reported as D-dimer level<0.5ug/ml> -Semi Quantitative Determination-
1) 5 test circles are labelled as 1:2, 1:4, 1:8,1:16 and 1:32.
2) 20uL of D-dimer reagent is added to all the 5 test circles.
3) Similarly, 20ul of buffer is added to all the 5 test circles.
4) 20ul of patient's plasma is added to only the test circle labelled 1:2.
5) The patient's plasma is serially diluted with the buffer in the remaining test circles.
6) The reagent in the test circles are mixed using a mixing rod, in the following sequence, from 1:32 to 1:16 to 1:8 to 1:4 to 1:2.
7)The test card is manually rotated with 2 mins.
8) When 2 min is up, check for agglutination.
9) Plasma D-dimer levels are obtained by multiplying the dilution number by 0.5ug/ml. E.g. If 1:8 is the highest dilution that produces agglutination, the plasma D-dimer level=0.5ug/ml x8= 4ug/ml. Hence, plasma D-dimer level is reported as >4ug/ml.
Maybe this diagram cn help you'll to understand better..
Finally..That's the end of my post. Have fun reading it ahh.
Cheong Shu Hui
TG02
0503277F
D-dimer Test (coagulation test)
The specific degradation of fibrin(i.e. fibrinolysis) is the mechanism responding to fibrin formation. Plasmin is the fibrinolytic enzyme that degrades fibrin into D-dimer. Hence, its appearance in the plama indicates that the fibrinolytic system is working in response to coagulation activation.
Coagulation Activation Plasmin
Fibrinogen -------------->Fibrin------------>D-dimer
D-dimers are crossed-linked degradation products of fibrin. D-Dimers are often associated with deep venous thrombosis(DVT), disseminated intravascular coagulation(DIC) and embolisms.
Hence, D-dimer can serve as a screening test for DVT.
Test Principle
D-Dimer test is a rapid latex agglutionation slide test that uses mouse monoclonal antibodies for semi-quantitative determination of D-dimer in the human plasma. The latex particles in the D-dimer reagent are coated with mouse anti-human D-dimer monoclonal antibodies. If the patient's plasma contains D-Dimes, it will cause agglutination when mixed with the latex particle suspension.
Test Procedure
1) The patient's plasma sample is checked against the name on the lab test request form.
-Neat Report-
2) 20uL of patient's plasma is pipetted into 1 circle on the black test card.
3) 20uL of D-dimer reagent is pipetted into the same circle on the test card.
4) The 2 drops on the test card are mixed using a mixing rod.
5) The test card is manually rotated for 2 mins in a manner such that the liquid swirls around the entire test circle.
6) When 2 min is up, check for agglutioination (i.e.bluish-white dots).
7) If no agglutination is observed, it is reported as D-dimer level<0.5ug/ml>
If agglutination is observed, proceed to semi-quantitative determination of D-dimer using serial dilution.
1) 5 test circles are labelled as 1:2, 1:4, 1:8,1:16 and 1:32.
2) 20uL of D-dimer reagent is added to all the 5 test circles.
3) Similarly, 20ul of buffer is added to all the 5 test circles.
4) 20ul of patient's plasma is added to only the test circle labelled 1:2.
5) The patient's plasma is serially diluted with the buffer in the remaining test circles.
6) The reagent in the test circles are mixed using a mixing rod, in the following sequence, from 1:32 to 1:16 to 1:8 to 1:4 to 1:2.
7)The test card is manually rotated with 2 mins.
8) When 2 min is up, check for agglutination.
9) Plasma D-dimer levels are obtained by multiplying the dilution number by 0.5ug/ml. E.g. If 1:8 is the highest dilution that produces agglutination, the plasma D-dimer level=0.5ug/ml x8= 4ug/ml. Hence, plasma D-dimer level is reported as >4ug/ml.
Maybe this diagram cn help you'll to understand better..
Finally..That's the end of my post. Have fun reading it ahh.
Cheong Shu Hui
TG02
0503277F
11 comments:
Dear Shu Hui
May i ask what is the reference range value for D-dimer
Thank
Ching Wei
hey shu hui,
You mentioned "D-Dimers are often associated with deep venous thrombosis(DVT).
Hence, D-dimer can serve as a screening test for DVT." How exactly is D-Dimer related with DVT? Is it that D-dimer is absent in patients with DVT?
Sally
TG02
hi Shu Hui
hey you mentioned that D-dimer's appearance in the plama indicates that the fibrinolytic system is working in response to coagulation activation. HOw do u exactly measure that agglutination. THey may be agglutination and like u said u will record it as <0.5ug/ml>. Even if there is more or less aggluinnation, you will still report that as <0.5ug/ml>?? No (range or)exact value can be obtained for the aggluination?
Vinodhini
TGO2
Hey,
Just want to find out for the D-dimer test, would you receive the sample as whole blood? and therefore require spinning down before the test?
Thanks,
Randall
TG02
heyheys SHUHUI,
1) what are the possible results when D-dimer is used as a screening test for DVT?
2) what's the D-dimer reagent and buffer used for?
thanks :)
dorothy
TG01
Hey Ching Wei
The reference range for D-dimer is <0.5ug/ml.
Hey Sally
DVT is formation of a blood clot in a deep vein. When a fibrin clot forms, the body’s response is to degrade it, and D-dimer is the terminal fragment of fibrin. Hence, an elevated D-dimer lvl may indicate thrombosis as patients with DVT usually have increased fibrinolysis.
Hey Vino
U will first have to perform a neat report to check for agglutination. The steps are there in my post. After which if there’s agglutination( no matter how weak tt agglutination is), we will proceed to semi-quantitative determination to quantitate the level of D-dimer (i.e.agglutination). If there’s no agglutination in the neat report, it is recorded as just <0.5ug/ ml, and this means negative results.
To find out the exact D-dimer lvl, we will have to find out what is the highest dilution that produces agglutionation. Therefore, if u observe agglutination for 1:2 and 1:4, the D-dimer lvl = 0.5ug/ml x 4= ≥2.0ug/ml. The lab im in dun give exact value.
Hey randall
Yes, the sample is received as whole blood in a sodium citrate tube. We have to spin down to get the plasma for testing.
Hey Dorothy
1)D-dimer result may be positive or negative cuz an elevated D-dimer lvl does not necessarily confirms DVT. Bt often, a high D-dimer lvl is indicative of DVT.
2)The D-dimer reagent contains latex particles coated with anti-human D-dimer monoclonal Ab. If the patient has D-dimers, it will cause agglutination with the Ab-coated latex particles. The buffer is used for serial dilution.
Hey Shu Hui,
Is there any limitations for this particular test? Look forward to ur reply. thanks! =)
Doreen (tg 01)
hello doreen,
high levels of rheumatoid factor may lead to false positive D-dimer results. Also, the presence of fibrinogen at a level >9g/l may lead to over-estimation of D-dimer.
Hello Shu Hui,
Will abnormal levels of D-Dimer affect routine PT and APTT results?
Just wondering, does your lab receive many D-Dimer test requests? Cos the test is run under automation in my lab!
Looking forward to your reply. Thank you.
-Alex Tg02
hi alex
nope, PT and PTT results are not afected by abnormal levels of D-dimer cuz PT and PTT are looking at coagulation factors while D-dimer aims at fibrinogen. huh?! D-dimer can be automated?! haha..maybe u can post pics of it in ur nxt post?
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