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HIV ELISA test and HIV ECLIA test

I have had many questions with regards to the ECLIA test and how it measures up against the ELISA test. Of course many people are very worried that their tests by ECLIA are not as reliable as the very well studied ELISA test. It’s time to put an end to the mystery once and for all.

Before we even get down to the tests themselves, we have to understand a little about how the human immune system works.

Our bodies do not like anything that is foreign (insert right wing French government joke here). When a virus enters the body, the body recognizes it as foreign and tries to get rid of it.

One whole virus is too much for the body to deal with. It needs specific targets to attack. These specific targets are little bits of protein on the virus called antigens.

The body produces antibodies that are unique and specific to these antigens and act like smart bombs to seek out and kill the virus.

So the presence of an antibody to a particular antigen indicates the presence of the virus.

So far so good?

Let’s not forget that antibodies are also antigens themselves. The antibody is made up of a head that is unique and specific and attaches to a particular antigen and a tail that can be recognized by other antibodies as a foreign antigen.

This fundamental science forms the basis of immuno testing which includes the ELISA and ECLIA tests.

So with all that background, let’s get back to the clinical scenario.

In the 1980s, HIV was finally identified as the pathogen that caused AIDS. The big problem was we needed a way to tell if someone was infected with HIV or not.

The most obvious method was to look for antibodies to HIV in the body.

So the medical profession turned to the ELISA test.

This is how the test was performed (nb: there have been great changes in ELISA technology over the years. For more info, look out for my next post: the different generations of ELISA).

First get a plastic board with a hole in it.
Stick bits of HIV antigen on the walls of this well.

 

 

 

Fill the well up with the patient’s serum.
If the serum contains antibodies to HIV, the antibodies will stick to the antigens on the wall.

 

 

 

The only problem that remains is how do we tell if any antibodies have stuck? Do not forget that these are tiny invisible molecules.

One ingenious method was to make an antibody that we can see and attach it to the antibody that is stuck on the wall of the well. Remember antibodies are antigens too?

The earliest methods made this so-called secondary antibody radioactive so its presence could be detected with a Geiger counter. I guess the scientist figured out real quickly that this wasn’t a really good idea.

Another technique involved attaching an enzyme to the secondary antibody. This enzyme causes a color change when a color substrate is added. And thus the ELISA test was born.

 

 

Lately, another technique was developed. It involved attaching a chemical to the secondary antibody that would glow when an electrical current was passed through it. And the ECLIA technique was born.

 

 

So to answer the question which is more accurate? Well, both tests are inherently really good and theoretically nothing short of genius. However, all medical tests have an inherent inaccuracy.  I will discuss this in more details in my next post : the different generations of ELISA.

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About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.

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65 Comments

  1. Nice explanation. you are genius.

  2. Dear Dr,
    I recently got involved in a risky sexual encounter through mutual masturbation where I used the semen of the partner as a lubricant. I only learnt afterwards that the fellow is actually HIV positive.

    It has been three weeks now and I have since developed a scratchy throat with flu like symptoms as if I want to cough – and when I do cough it is a dry cough. I need to mention that I do have sinusitis problem but never in my life have experienced scratchy throat as a result of sinuses or even just scratchy/sore throat for that matter.
    I went to test yesterday and the results came back negative says the Rapid test. I am curious to know whether 3 weeks is enough since some Drs say 4 weeks is suffice for the body to produce antibodies. I am asking this question in light of the fact that Rapid is more sensitive than Elisa?

    Also may I ask you to explain the possibility of catching hiv given the peculiar nature of my sexual encounter (semen as a lubricant).

    Please attend to my query as I am quite anxious.

    Thanking you in advance

    • Hi Elle,

      You say you used semen as a lubricant for mutual mastrubation. This may seem silly and I apologize in advance but are you male or female? The risk would certainly be higher if you were female as I assume you would be introducing infected semen into your vagina. There is also risk if you are male as the infected semen would have come into contact with your foreskin and urehtral opening. The good news is a rapid test (if done correctly) is very accurate at 3 weeks. It is certainly not conclusive and you must must must go back for a retest. However, you can be quite reassured with the result. And please don’t say things like ‘Please attend to my query as I am quite anxious’. First you make it sound like I am obliged to answer your question which really takes away the whole altruistic feel from this forum. Second you imply that I should answer your question because you are anxious so I should not answer everyone else’s question because they are not as anxious? Just chill dude (or dudette) I will answer everyone’s questions. But have a little patience cos I run a really busy clinic.

      rgds

      Dr Tan
      Help test out our new forum at http://www.askdrtan.com

      • Many thanks indeed Dr Tan and I do apologise in advance for having made such remarks. By no means did I intend to make my question/problem to be of greater importance than the rest or that you are obliged to attend to it. I think it was simply axiety speaking and indeed I do appreciate your kindness for taking time to answer our questions. Very appreciated.

        To answer your question, yes I am a male and I did use semen as a lubricant although I am circumcised.

        Thanks for allaying my fears whilst I remain affirmative that I need to have the test redone in 6weeks time.What do u think the sore throat could be ascribed to if it is not indicative of seroconversion?

        • Hi Elle,

          There are many causes of sore throat from a common cold to tonsillitis to throat cancer. I say this again for you and all other users of this forum. This is NOT a platform for medical consultation. I cannot diagnose your sore throat over the Internet. Please go see your doctor.

          Dr Tan
          Check out our new forum at http://www.askdrtan.com

  3. Dear Dr.Tan,

    I´m writing you to clarify some doubts:

    Could you tell me the hepatitis C window period?

    Could you tell me a safe window period for a 4th generation HIV Test (Elisa)? Had make sex with a HIV positive person could change this window period?

    Thanks a lot.

  4. Dear Dr. Tan

    +- six weeks after the abovementioned encounter, I have decided to ask the doctor to have my blood sample examined in the pathology lab. As previously stated, I had taken my a rapid test and result was negative. I am elated to inform you that the ‘official’ results came back negative. Thanks for your previous counsel as regards to this matter.

    But if there is anything I can draw from this experience is that one needs to cherish their lives too much not to expose themselves to risky behaviours.Also in the face of anxiety and desperation to find answers regarding the outcome of one’s risky sexual encounters, the internet is the wrong place to be seeking diagnosis. What it does instead is that your fears are compounded and you thus end up living like a zombie. But of course, it is one good starting point towards understanding the intricacies and innermost workings of HIV.

    Cheers

  5. Dear DR. Tan,

    You really think that im free from Hiv.

    i feel the same ,but sometime my mind start thinking that one year back when i test myself negative its becouse my body was not able to creat that amount of antibodies to detect .

    but second thing is its almost 1 year passed after my 3Negative HIV antibody test and health is very fine almost put on 5 kg. very healthy .

    doctor please dont let go this question as its senseless question .

    Doc please explain me in proper way so i can relax.

    So many forum i searched ans was its antibody test negative means conclusive after 5 years.but

    but somewhere i got this information…
    Antibody test comes false negative when person is at end stage of hiv…

    i have taken CBC report also after all my hiv antibody test , my report is very fine
    WBC – was normal

    i request you to explain me to clear my doubts..

    please please please help me Doc.

  6. HI Doctor,
    i had unsafe sex (condom breakage during intercourse) with sex worker on 27 November, 2011 and i conducted Anti HIV (ICT) Test on March 8, 2012. The result shows negative but still i’m not sure of it. I lost my 15 kg of weight during last 7 months. Which is the best and accurate HIV test that i should conduct now? Is there possibility of getting HIV from oral sex?
    Thank you.
    Regards,
    Pankaj

  7. I have just had ECLIA test done…

    HIV 1&2 ……. Reactive (811.4)

    Test Result 36.0 Cutoff rate = 1.0

    Western Blot test is pending…

    Can you tell me how serious trouble I could be in? What should be my next course of action?

  8. Hi Doctor,
    I had a unprotected sex about 7 weeks ago , now I have had ECLIA test HIV 1 & 2 ab/ag, and the result is “not detected”. I wanna know that 95% accuracy is just within 4-6 weeks or after 6 weeks also the accuracy is around 95%. TQ

  9. Hi Dr. Tan. My name is Alex and I’m from the Philippines. I had a low risk sexual activity last August 16 with a male sex worker. We used condom but what bothers me is due to hard penetration my anus got hurt so I had a test last September 6 the method is ECLIA ELECSYS 2010 and the result is non reactive, my value count is 0.339. Then I took a retest last September 29 again the result is non reactive, my count value is 0.409. I asked the staff in the diagnostic center where I took the test about the count value and they said what is important is I’m negative thou they did not explained it to me in detailed maybe because they don’t want me to worry. Dr. Tan what is the proper explanation about the count value for HIV? Since the cut off value is 1 and my last test was 0.409 is different from my first test result. And Dr for you three weeks and Six weeks negative result is highly conclusive using the ECLIA ELECYS 2010? Thank you Dr. Tan

    • The increase in counts is due to antibody cross reaction and has nothing to do with whether you have HIV or not. The results are very accurate at 6 weeks but most health authorities will still recommend a retest at 3 months. Please ask any follow up questions on http://www.askdrtan.com

  10. Dear Dr.Tan,

    I have just received my ECLIA Test results today and both HIV1 & 2 came out negative. I did the test roughly 10 – 11 weeks after the risky encounter. Do you think I am doing fine? Or should i get tested again and what other tests should I go for to confirm the results?

    Thank you so much for your valuable contributions.

  11. would i need to be sick or have fever in order to go for eclia test?

  12. dear dr..
    i had made test after possible expore 1 year.result
    eclia method(hiv 1/2 ag/ab)result not detected.

    i wanna khow is conclusive is eclia method

  13. Dear Dr, I had sex with a filipino domestic helper on May 1, 2012. Since then I have had strange symptoms. Such as painful lymph nodes, flu, sore throat, severe fungal infection in groin. I got hold of the lady, few days back and she said she had her 6 month HIV medical in June(no specific date), and all were fine. I know testing can change from place to place. But generally speaking is it ECLIA or ELISA? It seems Oraquick & Determine is used for rapid tests? Are they ELISA? Assuming she did her HIV test in June 1s week, how accurate is a negative test at 4 weeks?

  14. Hi Doctor,

    Greetings from Malaysia. Is the architect EIA same as ECLIA? Unfortunately my Doctor says he is not hiv doctor and was uncertain.

    Is test on EIA on 35 days conclusive?

    Thank you

  15. Helo DR. I had sex with a CSW and condom broke. I tested at 5 week and 6 week post exposure by Eclia Ag/Ab test, both non reactive. Are my tests conclusive?? I have had a dry throat of late with white coating on my tounge..Thanks..

  16. Hello Dr, i just had sex with a prostitute. So i was afraid if I could have any chance of getting HIV as i had protected sex. After 3 days, i only had flu and i would like to know if there would be any chance of contracting HIV as i have flu? Please advice whether i should inform my parents about it.
    Thanks!

    • You have a small but finite risk of contracting HIV from protected sex. Please post any follow up questions on http://www.askdrtan.com

      • I undergo 3 times of test for HBs Ag last Jan 16,19 and 24, 2013 using ELISA and ECLIA method for testing and all the result is reactive (cut off index is 1.0 and i have a result of 31.31). Feb. 26, 2013, I undergo again the same test HBs Ag using ELISA method and i got a result of 0.036 non-reactive. It is really posible that I make it down to non reactive again after almost 1 and a hallf months?

        • I do not know when your exposure was. HBs Ag at 1.5 months post exposure is very indicative.

  17. Hello Doctor,

    I had protected intercourse with a sex worker 3 weeks back (5 February 2013). I had a test today(3rd March) & the results (below) came out negative.

    HIV Combi (p24 Ag / HIV 1 & 2 Ab), serum
    by ECLIA – NON REACTIVE (0.285)

    Is the test & results reliable?? Please advice as I am scared & been having a running nose(on and off) for 3 weeks now …Thank you very much in advance.

    • I do not think a combo test is conclusive at 3 weeks.

      • Hello ,

        Thanks for the honest feedback. On the same day I did a HIV-1 Qualitative Real Time PCR test from another doctor. The result came out negative (they didnt mention the number).

        Below are the details about my blood sample.

        Sample Date:
        03-03-2013
        Report Date:
        05-03-2013

        Is the result indicative i am free from HIV? Please note that the result was based 3 weeks after my incident. I have been having dry lips , dry skin on my face and hands & feeling itchy on my neck & scalp. Please help!!

  18. Gonzalo

    Hello Dr
    I need your Help!
    Im from Argentina, i had a risk sexual relation on January 14th.
    I have a non reactive result from march 13th (8 weeks). with ECLIA 4th generation, its conclusive?
    Thanks!

  19. Hi Dr,

    You are doing a great job here and god bless you. I have been in this situation for over a month now. i am very scared and paranoid.

    I am a male and I had protected sex with a female csw(oral an Vaginal) with condom. This incident happened on 13th Feb, i have been worried since then. Two days back(20th March) I decided I will go in for a test, when I went they suggested me ECLIA test which I had never heard of nor was sure about how accurate it was. Thanks to you post here details are much clearer. Still to clarify, I had a negative result, how accurate is this at 34 days or 4 weeks?

    Can i be in peace? Is it conclusive? or at least how much accurate?

    Thanks Doc,
    Nik

  20. Hi Dr. Tan

    I had three unprotected sex last Dec to January of first week. Turns out that my partner was hiv+. I took the rapid ict test April 8, 2012. It was non reactive. Is it 100% accurate? Does it really mean I am nt infected? We are in an open relationship meaning he does casual sex while I do not.

    Do you think after 4 months it is conclusive already?

    Thank you and I am hoping for your response.
    God bless you Dr. Tan

    • I have not heard of the rapid ict test. Generally speaking, a 3rd Gen ELISA HIV antibody test at 3 months is more than enough to be conclusive. Please post any follow up questions on http://www.askdrtan.com

  21. Dear dr Tan,
    We have a bombing news to my family this week as we know our father in laws has been tested hiv with positive result , Recently he has become week and bad appetite, and as we are very worry about the family members if have been infected by this virus, some of us has been done the Eclia test after knowing this matter and it’s negative, but we hv been told that this is not 100% free of HIV due it’s a window period time.
    My concern is my children which are his grandchild, they are baby and toddler, do we need to bring them to do the HIV test? As before he know he has HIV, he ever hug and share food with my toddler,
    Can we stay with HIV person in a same house? If yes , what have we do to avoid infection of HIV,

    Thank u

    Fion

  22. Hi Dr Tan…

    I had a sex with sex worker about 3-4 months back. Now i went for medical test. All the reports are fine except HIV1 and 2.

    My report says:
    HIV1 and HIV2 Screeing (Serum): Method: ECLIA
    Findings: 0.673 (Non-reactive).

    Still I don’t have any health issues. But I am very tensed since i got my report.

    Can you please suggest is there any chance of infection or di i need to go for another test in some time.
    Thanks in advance…

  23. hi Dr. Tan,

    Sorry, I know this may me some foolish question..but I just need to clarify it myself.

    I had a sex with prostitutes and I have a HIV test after 4 month and it’s negative. I cant remember what method the doctor is using but I’m guessing its ECLIA.

    Just to clarify, with any method of test..4 month is accurate enough ? and if using ECLIA method..is it accurate enough? Do I need to get a retest? since i heard some people said it should be accurate 6 month after exposure.

    sorry i just need to clear up my mind.

    thanks !

  24. Hi! My name is Baros from Manila, my last unprotected sex was Aug 2012, I was so paranoid, and since then I practice abstinece, I undergone Rapid ICT test last Oct 2012 result was non-reactive to hiv-1 and hiv-2 in Manila. then this year of May 2013 I undergo Rapid ICT test and result was non-reactive to hiv-1 and hiv-2. Still I practice abstince. Total of 9 months has pass. I got worried when I found out that my ex-partner is now Hiv possitive this June 2013. We havent had sex or any contact since Aug of 2012. After two test of negative results. Pls advice me, of what to do? how accurate was this test. Im now practicing abstinence since Aug 2012.

    Thank you!
    Baros

  25. muhammad Ali

    hello sir.

    my english is little weak but i understand what i want to ask.sir i had sex with a prostituate on last 26 july2013.then i become very upset and still iam upset.i did a hiv i@ii on eclia method that was negative and then i did a vdrl test after one month that was negative and then i did hiv i#ii on eclia method after 65 days having sex that was also negative.do u think its enough for me…i mean for my satisfaction

    • I think your tests are really as good as conclusive. However the recommended official window period is still 3 months.

  26. Victor Valentine

    I tested positive with a faint line on determine Alere kit. I have gone for ELISA and the result came out negative. It’s just 2months since I had sex with a prostitute, but I used a condom. I’m scared. I tested my self for HBSAG and HCV and they all came out negative. Why would determine alere show me faint line?

    • There is always a risk of false positive results with any HIV screening test including the Determine. That is why we always follow up a positive screening test with a confirmatory test.

  27. Christopher

    Dear Doctor,
    My test results :
    ECLIA : Reactive
    Serodia PA : Agglutination to HIV-1 detected
    Immunoblot : Antibodies to HIV-1 detected

    what do they mean ? thanks

    • It means you are possibly infected with HIV. You MUST speak to the doctor who ordered this test for you.

  28. Dear sir….I am very tense as being a physician …. More than two years back I had multiple sex exposure to prostitute…. I was obese…. Recently I was loosing weight very fast…. Dandruff in scalp is more… Skin is dry…. For your info I was also trying to loose weight to become slim and this is winter season … I stay near salty sea water… I tested rapid ICT test for HIV and its negative but as a doctors mind, I am always suspicious and tense… 1.5 yrs back I tested Elisa and it was below cut off point…. What can do now? I am married with feeding baby… I don’t want to destroy their life

  29. dear doctor after 8 weeks the result was ECLIA 0,600, are great chances that the 12 week change in a positive, cordial greeting

  30. MISTAKEN BOY

    I am 24 years Old. I had unprotected Sex with a LADY. Then I got worried and did two check up. after one month of incident I did HIV TEST BY PCR. It came Negative and AFTER TWO MONTHS i DID HIV ECLIA Test. and Result fortunately again came negative but the range was Non-Reactive (0.154) This level made me worried. Please Advise on my situation.

  31. doctor, i had an unprotected fellatio 8 months back. I have done eclia test at 4 months, result was 0.3, at just 10days less than 8months, i did it again. Result is non reactive, but value had increased to 0.72..this increase is worrying me..will it cross the limit of 0.9 im few more months? Pls reply sir…

  32. had a protected oral and a protected vaginal sex with a legal geylang csw on april 19 2014 . I developed fatigue in a week and also pharyngitis , sinusitis , fever(3days , not very high ) , chills at 3 weeks post exposure . Then I also had weakness and leg pain for 2 months. I also had lymphocytes 18% at 2 weeks post exp and 56% 4 weeks post exp .
    I did elsia hiv antibody 1 n 2 test , card method at 8 weeks . It came out negative ( d lab said its strongly negative ) . Do I hav to test again ??? Pls giv yr opinion

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