Aa
CDC cases (rare)
I was wondering if anyone had read about the rare cases in which people tested negative on the antibody test and positive on the Western Blot after the window period (read on The Body)... Were those people already immunocomprimise: ie cancer or some other disease, or had they already progressed to AIDS and were somehow unable to produce the antibodies anymore? Why would that happen.
Doctors offer WB and ELISA at the same time in some countries where the patient pays for all his tests. In Canada they dont offer the WB test as patient is not paying for it, and the health ministry does the WB only when ELISA is positive.
Its not possible to have ELISA neg and WB poz
Western Blot should never be done without a positive ELISA. They are both antibody tests, by the way, so both are looking for the same thing. ELISA is a quicker, cheaper and a more sensitive test, so it is the optimal choice for a screening test.
I didnt say someone has antibody and doesnt have hiv. you might start a new thread.
But was asking if possible that a screening test doesnt find HIV antibody and WB would do because it is more specific. If there is a doubt about a negative screening test, could WB be ordered to confirm?
But was asking if possible that a screening test doesnt find HIV antibody and WB would do because it is more specific. If there is a doubt about a negative screening test, could WB be ordered to confirm?
I am a little confused. How can you have the antibody for HIV and not have HIV.
I think I have an idea.
Here is my experience. Because I was born in another country and had the BCG tuberculosis vaccination ( it is not used in the States) I always come out positive on the TB skin test. I don't understand the science behind it.My specialty is infertility research. I always have to get a chest xray to prove I don't have TB. I always come out positive on that dog gone skin test but negative on the xray..
Then I ask myself , what is a vaccine? A vaccine is when you are inoculated with the same germ you want to be protected against. The germ is usually dead or altered or weakened. So if they are looking for the TB germ in me then they will find it because I was inoculated with the germ when I was a baby when I got my BCG vaccine.
The germ the skin test is looking for and always finds is actually keeping me immune from the disease.
Is this the same for HIV? Why do some people test positive for the antibody but not have HIV? I read an article that claims that some people are immune to HIV. i don't know if this is true or not. I wouldn't trust it until the CDC puts it out there.
Have these people been vaccinated by some means (unknown to us or themselves or by accident by some unknown means)?Read the history of vaccine and you will see all the WONDERFUL accidents that happened that are still in use today.
My colleague does HIV research not counseling. He started a research lab in my country to study some people who are immune to TB or who received the BCG vaccine.Americans don't use this vaccine but he is hoping that if he does a good job on the research he can present the results to the scholars here. He thinks there is something to be discovered with these people who seem to be immune for HIV.
I had a little HIV scare a little while a back and everyone was saying you are not at risk. Well I did talk to him about it. He said, " I am not a counselor I am a researcher and theoretically ...... and statistically ............. Very intelligent man but scared the hell out of me with his theories..I had to visit my Shrink colleague and she refused to counsel me. What a life? I am HIV negative but still messed up in the mind.
I think I have an idea.
Here is my experience. Because I was born in another country and had the BCG tuberculosis vaccination ( it is not used in the States) I always come out positive on the TB skin test. I don't understand the science behind it.My specialty is infertility research. I always have to get a chest xray to prove I don't have TB. I always come out positive on that dog gone skin test but negative on the xray..
Then I ask myself , what is a vaccine? A vaccine is when you are inoculated with the same germ you want to be protected against. The germ is usually dead or altered or weakened. So if they are looking for the TB germ in me then they will find it because I was inoculated with the germ when I was a baby when I got my BCG vaccine.
The germ the skin test is looking for and always finds is actually keeping me immune from the disease.
Is this the same for HIV? Why do some people test positive for the antibody but not have HIV? I read an article that claims that some people are immune to HIV. i don't know if this is true or not. I wouldn't trust it until the CDC puts it out there.
Have these people been vaccinated by some means (unknown to us or themselves or by accident by some unknown means)?Read the history of vaccine and you will see all the WONDERFUL accidents that happened that are still in use today.
My colleague does HIV research not counseling. He started a research lab in my country to study some people who are immune to TB or who received the BCG vaccine.Americans don't use this vaccine but he is hoping that if he does a good job on the research he can present the results to the scholars here. He thinks there is something to be discovered with these people who seem to be immune for HIV.
I had a little HIV scare a little while a back and everyone was saying you are not at risk. Well I did talk to him about it. He said, " I am not a counselor I am a researcher and theoretically ...... and statistically ............. Very intelligent man but scared the hell out of me with his theories..I had to visit my Shrink colleague and she refused to counsel me. What a life? I am HIV negative but still messed up in the mind.
Thanks, i knew that procedure. But was asking if possible that a screening test doesnt find HIV antibody and WB would do because it is more specific. If there is a doubt about a negative screening test, could WB be ordered to confirm?
Try to understand what I said. If you had a risk get an antibody test. If the antibody test is positive they well then do a Western Blot to confirm it.
Teak, Are you saying that there is NO WAY screening test is negative and Western Blot would be positive? Is it because they both look for antibody?
Most of the people that come on here and state such are lying out their teeth to be quite honest.
i have read several times where ppl have come on here with repeated negative test results...but have posted they had taken western blots and viral load tests. knowing that a western blot is used to comfirm an antibody test...how are the able to get these done? do there doctors finally just order these to shut them up?
If someone tests after 3 month negative on antibody test which is 99.8% sensitive , but with a high chance to be infected, is recommended to take Western Blot (for its high specificity) to absolutely rule out HIV?
Western blot is the antibody test. If you test positive on the Western Blot means you have antibodies to HIV
This is the Info I got from the Western Blot
Source http://hivinsite.ucsf.edu/InSite?page=kb-02-02-01#S10.1X
Western Blot Test
Methodology
The Western blot probably is the most widely accepted confirmatory assay for the detection of antibodies to the retroviruses. Most authorities consider it the gold standard for validation of HIV results. It is based on using an electrophoretic technique to separate HIV antigens derived from a lysate of virus grown in culture. This technique denatures the viral components, imparts a negative charge to the antigens, and separates them primarily on the basis of their molecular weights. The separation of antigens in the technique allows for the identification of specific antibodies to each of the viral antigens in a subsequent set of steps similar to the ELISA methodology.
A purified HIV antigen mixture is layered onto a sodium dodecyl sulphate (SDS) polyacrylamide gel slab and then electrophoresed. The viral proteins (HIV antigens) migrate through the molecular pores of the gel at rates determined by electrical charge and molecular weight. The proteins with higher molecular weight migrate less and form bands closer to the starting point. The proteins on the gel are then transferred ("blotted") to nitrocellulose paper by another electrophoretic procedure. This paper is cut into thin strips, each with the full distribution of viral protein antigen bands. A single test strip is incubated with a 1:50 or 1:100 dilution of a test sample or a control and then washed and incubated with a labeled (tagged) antihuman globulin. At this point, the procedure is similar to any other indirect immunoassay. The label usually is an enzyme (horseradish peroxidase or alkaline phosphatase) that will react with a specific colorless substrate to produce an insoluble colored band on the strip wherever there is an antigen-antibody complex. Reaction with a positive serum sample produces a pattern of bands on the strip that is characteristic of HIV. Many of these bands have been identified as specific viral gene products.
The HIV-1 viral antigens are separated as follows (from top to bottom): gp160, gp120, p66, p55, p51, gp41, p31, p24, p17, and p15 (Figure 1). The "gp" designation refers to glycoproteins; "p" indicates proteins. The numeric values (x100) indicate molecular weights. It is important to remember that nonviral proteins derived from the host cells in which the virus was grown also are present on the nitrocellulose strip. They can form bands in many places, but often are near the middle molecular weight (40,000 to 60,000) region. These nonviral protein bands may produce difficulty in interpretation of results by producing nonspecific reactions.
Interpretation of Results
Depending on the particular antibodies in the sample, reactivities with the separated antigenic components result in band profiles. The type of profile (the combination and intensity of bands that are present) determines whether the individual is considered positive for antibodies to HIV. The classification of Western blot results is determined by certain criteria. Most institutions now follow the CDC guidelines, which require reactivity to at least 2 of the following antigens: p24, gp41, gp120/160 for a positive classification. It is now universally accepted that a negative result is the absence of all bands. Two organizations, however, including the World Health Organization (WHO), suggest that results also can be reported as negative if there is only a very weak p17 band. Indeterminate classifications occur when there is reactivity to 1 or more antigens, but not fulfilling the criteria for positivity. Figure 1 depicts examples of positive, negative, and indeterminate Western blot results.
Unfortunately, sera from some noninfected individuals show some reactivity to 1 or more antigens if tested by Western blot. This reactivity may occur in as many as 15% of normal noninfected persons, and many times occurs in persons who are nonreactive by screening assays. Therefore, if ELISA-nonreactive sera are tested by Western blot, many will result in an indeterminate profile. Most indeterminate results show only weak reactions to the Gag proteins (mostly p17, p24 and/or p55); other patterns occur but are less frequent. Any Western blot reactivity that does not meet the requirements for being positive or negative must be considered indeterminate.
Some individuals who exhibit indeterminate results (eg, reactivity to p24 and p55) later seroconvert, demonstrating that a p24 and p55 profile can indicate early infection. Conversely, other individuals may have the identical profile for long periods of time (years) and never seroconvert (ie, they are not infected). In fact, most indeterminate Western blot results from noninfected individuals exhibit the p24 and/or p55 profile. Therefore, an indeterminate Western blot result cannot predict early infection.
Most authorities suggest that persons with indeterminate results should be retested after several months, although seroconversion may be detected in a shorter period of time. If at all possible, the retesting of an individual at a later time should be performed in parallel with reassay of the initial sample on the same run with the same kit lot numbers and the same assay conditions to ensure that the samples can be compared directly. The WHO recommends retesting persons after 2 weeks if highly suggestive Western blot profiles are produced, although other organizations suggest waiting 1-6 months before retesting. If an individual is retested over a period of 6 months and becomes negative or the band profiles do not progress, infection with HIV generally can be ruled out. For poorly understood reasons, many individuals continue to exhibit indeterminate results for years but are not infected. If an individual does progress serologically (more bands or greater intensity of bands) or converts to positive (seroconversion) during retesting, the individual probably was infected at the time of the first test (early infection). It should be noted that individuals who have received vaccination for HIV (eg, subunit gp160) may be misidentified as positive based on reactions to the envelope antigens alone.
The significance of an indeterminate Western blot result varies depending on the risk factors, clinical status of the patient, and the Western blot profile produced. For example, individuals with a history of high-risk behavior are more likely to be the ones who later seroconvert, because the chances of their being infected are high. In addition, some Western blot profiles are more suggestive of early infection (eg, p24, p31, and p55) than are others (eg, p17 only). Many initially indeterminate results that subsequently become negative or remain indeterminate probably are a result of nonspecific reactions, hypergammaglobulinemia, the presence of cross-reactive antibodies, infection by HIV-2, or infection by an unknown, but related retrovirus. There have been a few reports where autoimmune diseases (eg, systemic lupus erythematosus) can cause false-positive HIV tests, including Western blot.(35) Also, it is known that some individuals with AIDS may lose reactivity to p24, and perhaps other antibodies, later in disease, so that even AIDS patients may have indeterminate Western blot results by some criteria. Ancillary tests, such as polymerase chain reaction (PCR) and viral culture may be helpful in resolving these indeterminate results if the diagnosis is in question.
Source http://hivinsite.ucsf.edu/InSite?page=kb-02-02-01#S10.1X
Western Blot Test
Methodology
The Western blot probably is the most widely accepted confirmatory assay for the detection of antibodies to the retroviruses. Most authorities consider it the gold standard for validation of HIV results. It is based on using an electrophoretic technique to separate HIV antigens derived from a lysate of virus grown in culture. This technique denatures the viral components, imparts a negative charge to the antigens, and separates them primarily on the basis of their molecular weights. The separation of antigens in the technique allows for the identification of specific antibodies to each of the viral antigens in a subsequent set of steps similar to the ELISA methodology.
A purified HIV antigen mixture is layered onto a sodium dodecyl sulphate (SDS) polyacrylamide gel slab and then electrophoresed. The viral proteins (HIV antigens) migrate through the molecular pores of the gel at rates determined by electrical charge and molecular weight. The proteins with higher molecular weight migrate less and form bands closer to the starting point. The proteins on the gel are then transferred ("blotted") to nitrocellulose paper by another electrophoretic procedure. This paper is cut into thin strips, each with the full distribution of viral protein antigen bands. A single test strip is incubated with a 1:50 or 1:100 dilution of a test sample or a control and then washed and incubated with a labeled (tagged) antihuman globulin. At this point, the procedure is similar to any other indirect immunoassay. The label usually is an enzyme (horseradish peroxidase or alkaline phosphatase) that will react with a specific colorless substrate to produce an insoluble colored band on the strip wherever there is an antigen-antibody complex. Reaction with a positive serum sample produces a pattern of bands on the strip that is characteristic of HIV. Many of these bands have been identified as specific viral gene products.
The HIV-1 viral antigens are separated as follows (from top to bottom): gp160, gp120, p66, p55, p51, gp41, p31, p24, p17, and p15 (Figure 1). The "gp" designation refers to glycoproteins; "p" indicates proteins. The numeric values (x100) indicate molecular weights. It is important to remember that nonviral proteins derived from the host cells in which the virus was grown also are present on the nitrocellulose strip. They can form bands in many places, but often are near the middle molecular weight (40,000 to 60,000) region. These nonviral protein bands may produce difficulty in interpretation of results by producing nonspecific reactions.
Interpretation of Results
Depending on the particular antibodies in the sample, reactivities with the separated antigenic components result in band profiles. The type of profile (the combination and intensity of bands that are present) determines whether the individual is considered positive for antibodies to HIV. The classification of Western blot results is determined by certain criteria. Most institutions now follow the CDC guidelines, which require reactivity to at least 2 of the following antigens: p24, gp41, gp120/160 for a positive classification. It is now universally accepted that a negative result is the absence of all bands. Two organizations, however, including the World Health Organization (WHO), suggest that results also can be reported as negative if there is only a very weak p17 band. Indeterminate classifications occur when there is reactivity to 1 or more antigens, but not fulfilling the criteria for positivity. Figure 1 depicts examples of positive, negative, and indeterminate Western blot results.
Unfortunately, sera from some noninfected individuals show some reactivity to 1 or more antigens if tested by Western blot. This reactivity may occur in as many as 15% of normal noninfected persons, and many times occurs in persons who are nonreactive by screening assays. Therefore, if ELISA-nonreactive sera are tested by Western blot, many will result in an indeterminate profile. Most indeterminate results show only weak reactions to the Gag proteins (mostly p17, p24 and/or p55); other patterns occur but are less frequent. Any Western blot reactivity that does not meet the requirements for being positive or negative must be considered indeterminate.
Some individuals who exhibit indeterminate results (eg, reactivity to p24 and p55) later seroconvert, demonstrating that a p24 and p55 profile can indicate early infection. Conversely, other individuals may have the identical profile for long periods of time (years) and never seroconvert (ie, they are not infected). In fact, most indeterminate Western blot results from noninfected individuals exhibit the p24 and/or p55 profile. Therefore, an indeterminate Western blot result cannot predict early infection.
Most authorities suggest that persons with indeterminate results should be retested after several months, although seroconversion may be detected in a shorter period of time. If at all possible, the retesting of an individual at a later time should be performed in parallel with reassay of the initial sample on the same run with the same kit lot numbers and the same assay conditions to ensure that the samples can be compared directly. The WHO recommends retesting persons after 2 weeks if highly suggestive Western blot profiles are produced, although other organizations suggest waiting 1-6 months before retesting. If an individual is retested over a period of 6 months and becomes negative or the band profiles do not progress, infection with HIV generally can be ruled out. For poorly understood reasons, many individuals continue to exhibit indeterminate results for years but are not infected. If an individual does progress serologically (more bands or greater intensity of bands) or converts to positive (seroconversion) during retesting, the individual probably was infected at the time of the first test (early infection). It should be noted that individuals who have received vaccination for HIV (eg, subunit gp160) may be misidentified as positive based on reactions to the envelope antigens alone.
The significance of an indeterminate Western blot result varies depending on the risk factors, clinical status of the patient, and the Western blot profile produced. For example, individuals with a history of high-risk behavior are more likely to be the ones who later seroconvert, because the chances of their being infected are high. In addition, some Western blot profiles are more suggestive of early infection (eg, p24, p31, and p55) than are others (eg, p17 only). Many initially indeterminate results that subsequently become negative or remain indeterminate probably are a result of nonspecific reactions, hypergammaglobulinemia, the presence of cross-reactive antibodies, infection by HIV-2, or infection by an unknown, but related retrovirus. There have been a few reports where autoimmune diseases (eg, systemic lupus erythematosus) can cause false-positive HIV tests, including Western blot.(35) Also, it is known that some individuals with AIDS may lose reactivity to p24, and perhaps other antibodies, later in disease, so that even AIDS patients may have indeterminate Western blot results by some criteria. Ancillary tests, such as polymerase chain reaction (PCR) and viral culture may be helpful in resolving these indeterminate results if the diagnosis is in question.
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