Q. Do you feel CMIA is better than ELISA?

Answered by
Dr. Prakash H Muddegowda
and medically reviewed by iCliniq medical review team.
This is a premium question & answer published on Nov 29, 2016 and last reviewed on: Nov 26, 2020

Hi doctor,

My CMIA on 177th day was nonreactive with an index of 1.4. My second CMIA on 181st day was also nonreactive with an index of 0.8. These two were done at different places. If you compare ELISA and CMIA combo for HIV antibody testing, which is better? What is the maximum window period of forming antibodies and what are the reasons behind the delay? If you compare rapid card test with CMIA, which is more sensitive and reliable? Based on my reports, can I consider it conclusively negative?

#

Hi,

Welcome to icliniq.com.

Based on your query and attached reports (attachment removed to protect patient identity), my opinion is as follows:

  • CMIA combo - chemiluminescent microparticle immunoassay is better as it detects both antigens and antibodies, whereas, ELISA (enzyme-linked immunosorbent assay) mainly detects only antibodies.
  • The window period is usually around three months. Depressed immune system or malnutrition can delay or reduce the formation of antibodies. However, antigen will be present and CMIA combo should be positive, if infected.
  • Rapid card is an emergency test and it is not as sensitive or reliable as CMIA combo.
  • Yes, you can safely assume yourself as negative and further tests are not necessary.

For further doubts consult a pathologist online --> https://www.icliniq.com/ask-a-doctor-online/pathologist

Thanks Sir for reply
Can Alcohol consumption has any impact on delay of antibody formation.
And if antibody are not formed in any case then also Antigen p24 will be present at six months.
Please help with your answer. I heard in most of the cases all infected persons should be positive by antibody test at six month.
# Hi,
Thanks for asking again.

1. Alcohol consumption if associated with malnutrition can reduce antibody formation. Like associated Vitamin or protein deficiencies in chronic alcoholics. Normal alcohol consumption with proper nutrition has no direct effect.
2. If antigen P24 is not positive within 3 months, then no possibility and if antibody is not formed and still p24 antigen is not formed, then no infection is present. Even if antibodies are delayed, antigen should have formed indicating infection. Here it has not formed, so no risk. No need to worry hence forth and no further tests necessary.
3. Yes, within 6 months, antibodies should be present, otherwise we usually declare case as no infection.

Hope it helps.
Any further queries, here to help again.
Thanks Sir for your reply
Still one query is from my side that if in case at six month antibodies are not formed in that condition p24 will be there for detection as I have read that p24 only remain exists initially 1-2 months.
So just want to ask that at 6 months either of these two[Either Antibodies or p24] will be present in absence of other at six month.

Second sir, in my attached reports only index for antibodies are mentioned and there is no reference of p24 although both were combo test.

will be thankful with your answer.

Regards
# Hi,
Thanks for asking again.
Based on your query, my opinion is as follows:

1. Antigen of virus is first released and in response to it, antibodies are formed to fight. Antigens are initially high in numbers, but as antibodies increase, they become undetectable. So, p24 antigen, if present will continue till antibodies are formed. If antibodies are formed as usually seen after 1-2 months, they disappear. Here, no infection, hence no antigen and hence no antibodies.
2. Yes, combo test usually detects both. If not present, possibly they might not report. Six month's, no antibodies, no possibility of infection. Not to worry.

Hope it helps.
Any further queries, here to help again.
Dear Sir

Seeking your expert comments on it suggestwd by my local dr.

For any infection, initially d antigens r released by d infective organism, to which d body reacts by producing antibodies.
However, in case of HIV, d antigen release is continuous and d virus deceives d antibodies produced by d body.
Hence, P24 antigen is detected all through out life if once infected.
In fact, it is used as one of d markers to determine d viral load later on in d disease course.
According to WHO guidelines, all HIV tests are conclusive at 12 weeks.
In case of CMIA, d results are accurate at 6 weeks post exposure and it is not possible for d test to miss d antigen or antibody at 6 months.
It is unlikely that ur results are goin to change to positive at 6 months and it is not recommended to test beyond 3 months if found negative.

Sir i had my both CMIA at 6 months.

Your repsonse will help me.

Regardd
# Hi,
Thanks for asking again.

Yes, all are correct. Antigen will always be present, but once antibodies are formed, it may become undetectable. As disease progresses, antibodies are not effective and hence antigen determines viral load.
Six months is more than adequate for tests to be positive. As there is no positivity, there is no chance of this exposure causing any disease. Be safe in future. Have a good life.

Hope it helps.
Any further queries, here to help again.

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