Name of Test: VDRL
Hello guys! Hope all of you are enjoying your SIP =)
For the first three days, I was attached to the Microbiology lab. I will be sharing with you about VDRL test which I was allowed to perform on urgent and routine specimens over the three days.
Test: Venereal Disease Research Laboratory (VDRL)
Principle:
- VDRL is a screening test for syphilis which is a Sexually-Transmitted Disease.
- Syphilis is caused by Treponema pallidum which is from the spirochetes group which consists of the spiral and motile bacteria.
- Reagin antibodies are produced when one is infected with syphilis. Reagin antibody is a mixture of IgM and IgG antibodies.
- This test uses nontreponemal antigens which are extracted from normal mammalian tissues. Lecithin and cholesterol are usually added to enhance the reaction.
- The reagent contains carbon particle cardiolipin antigens (extracted from beef heart) which will bind to the reagin antibodies causing visible clumping.
1. Cards with 10 circles measuring 18mm
Retrieved June 29,2008, from http://www.bd.com/ds/productCenter/DT-MacroVueComponents.asp
2. Plastic dispensing tubes (Dispenstirs)
Retrieved June 29, 2008, from http://www.bd.com/ds/productCenter/DT-MacroVueComponents.asp
3. Reagent
4. Patient's Serum
5. Rotator
Retrieved June 29, 2008, from http://www.bd.com/ds/productCenter/DT-MacroVueComponents.asp
Method:
1. Using the dispensing tubes, dispense 1 drop of patient's serum onto the one of the 18mm circles. Since there are 10 such circles on one card, the test can be done on 10 patients' serum at one go.
2. Spread the patient's serum using the flat part of the tubes as shown in the picture, making sure the serum does not flow out of the circle.
3. Dispense 1 free falling drop of reagent onto the serum.
4. Bend the card downwards using both of your hands to prevent the serum from entering into another circle when the card is being rotated.
5. Place the card on the rotator which rotates at 100 rpm for 8 minutes.
6. Read the results macroscopically by rotating and tilting the card 3-4 times in a to-and-fro motions
Results:
Retrieved 29 June, 2008 from http://www.bmb.leeds.ac.uk/mbiology/ug/ugteach/dental/tutorials/std/vdrlexplain.html
Upper left circle: results are reported as non-reactive as there is no clumping
Upper and lower right circles: results are reported as reactive as there is visible clumping
Note:
- Once, when the supervisor was performing the test, he got a reactive specimen. After which, he did serial dilution to determine the antibody titre.
- Both positive and negative control must be carried out using the control solutions which are available with the kit. This is to confirm that the reagent is working.
Reference:
1. http://www.bd.com/ds/technicalCenter/clsi/clsi-RPR.pdf
2.http://www.bmb.leeds.ac.uk/mbiology/ug/ugteach/dental/tutorials/std/vdrlexplain.html
3.http://www.bd.com/ds/productCenter/DT-MacroVueComponents.asp
2. Geo. F. Brooks., Karen C. Carroll., Janet S. Butel., & Stephen A. Morse. (2007). Medical Microbiology. USA: The McGraw-Hill Companies,Inc.
Name: Nur Farhana Binte Ramlan
Admin No: 0604834B
13 comments:
HEY FARHANA!(:
u mentioned that VDRL is a screening test for syphilis which is a Sexually-Transmitted Disease. but can it be used for other diseases and not specifically STD?
another question
u said that it uses nontreponemal antigens which are extracted from normal mammalian tissues. i dont really understand what you mean by nontreponemal antigens and how do we extract?
sorry uhh i blur. haha. k enjoy your sip! :))
Nur Liyanah Zaffre
0607718D
Tg02
Hello Farhana
I find the laboratory you are working in very interesting and I would like to know more.
1. Can you explain the host's primary and secondary immune response of the host after antigenic exposure to the bacteria Treponema pallicum?
2. Can you provide the definition of nontreponemal antigens?
3. Is it dangerous working with syphilis infected specimen and the bacterium? What types of safety measures have been put in place lest you are exposed to the bacteria?
4. Is the macro vue card test reliable? As in does false negative or false positive result appear sometimes and is it used in preliminary or confirmatory identification of the bacteria?
Thanks for answering my queries !! :)
Hello Farhana
I find the laboratory you are working in very interesting and I would like to know more.
1. Can you explain the host's primary and secondary immune response of the host after antigenic exposure to the bacteria Treponema pallicum?
2. Can you provide the definition of nontreponemal antigens?
3. Is it dangerous working with syphilis infected specimen and the bacterium? What types of safety measures have been put in place lest you are exposed to the bacteria?
4. Is the macro vue card test reliable? As in does false negative or false positive result appear sometimes and is it used in preliminary or confirmatory identification of the bacteria?
Thanks for answering my queries !! :)
Please ignore the previous comment (this is updated 1 )as i have forgotten to put my name ... zzz
From: Ma Xianwei Benjamin
0606181F
TG01
Hi!
You mention VDRL stands for venereal disease research lab, what does venereal mean?
And! Reagin antibodies, nontreponemal antigens and cardiolipin antigens seems very new to me, could you give me more information on them? Like how and where is reagin Ab produced? What is nontreponemal Ag? Does nontreponemal have a meaning? (meaning of the word)
Thanks!
Chew Yu Mei
TG01
1. No.. I don't think VDRL can be used for other diseases.
2. Nontreponemal antigens are antigens which do not originate from T.pallidum. There is a test called TPHA (a confirmatory test for syphilis) which uses treponemal antigens, meaning the antigens which originate from T.pallidum.Nontreponemal antigens can be extracted from mammalian tissues by using acidic solvents.
Thank you for your questions.
Nur Farhana
0604834B
Hello Benjamin..
1. I think the primary and secondary immune response of a person infected with T.pallidum is almost similar to other bacterial infections. That is, in the primary immune response, IgM will be produced whereas IgG will be produced in the secondary immune response. After treatment and during later phase of syphilis, IgM activity will slow down and IgG response will still be strong.
2.Nontreponemal antigens are antigens which do not originate from T.pallidum. There is a test called TPHA (a confirmatory test for syphilis) which uses treponemal antigens, meaning the antigens which originate from T.pallidum
3.Yes, we will have to treat the samples as potentially infectious. Thus, while carrying out this test, the medtech must wear gloves and labcoat. If there is any spillage of the samples, we must disinfect with 70% alcohol. We must not pipette by mouth. The dispensing tubes (dispenstirs) which are disposable must be treated as biohazardous waste.
4. Yes. False positive results may appear if the patient is suffering from other diseases like chicken pox, hepatitis, malaria and many more. False negative results may also appear if the patient is in the primary and tertiary phases of syphilis. VDRL is just a preliminary test for syphilis whereas TPHA is the confirmatory one.
Thank you for your questions.
Nur Farhana
0604834B
Hello Yu Mei..
1.Venereal means sexually-transmitted
2.Reagin antibodies are IgG and IgM type of antibodies. They are actually non-specific antibodies which are produced in many other types of infections other that syphilis. I think cardiolipin especially can react against these antibodies.
3. Cardiolipin is a diphosphatidylglycerol. It is especially abundant in animals' hearts. In this case, it is complexed with lecithin and cholesterol to enhance the reaction.
4. Nontreponemal antigens are antigens which do not originate from T.pallidum. There is a test called TPHA (a confirmatory test for syphilis) which uses treponemal antigens, meaning the antigens which originate from T.pallidum
Thank you for your questions.
Nur Farhana
0604834B
Good. Continue the good work.
What is the key difference between VDRL and TPHA? Why one if screening test and another is confirmatory test?
Hello Ms Chew =)
I believe the key difference between VDRL and TPHA is the type of antigens used in both tests. For VDRL,the reagent is made up of nontreponemal antigens complexed with lecithin and cholesterol. Thus, VDRL can only be a screening test because not only treponemal antibodies would react with the antigens, but other antibodies as well. Whereas in TPHA, the particles (reagent) are sensitised with T.pallidum antigens. Therefore, TPHA is the confirmatory test for syphilis bcause only treponemal antibodies can react with the treponemal antigens. It is thus more specific than VDRL. A patient with a positive TPHA would definitely have a reactive VDRL. Please correct me if I am wrong. Thank you =)
Nur Farhana
0604834B
You are correct. Keep up the good work.
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