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Inaccuracy of antibody testing
Hveragerthi Views: 5,836
Published: 9 years ago
This is a reply to # 1,548,978

Inaccuracy of antibody testing


These deal more with antibody testing for HIV, but antibody testing for hepatitis involves the same types of tests and are prone to the same inaccuracies.

Serological Tests Often Yield False-positive Results among HIV Vaccine Recipients

Recipients of investigational HIV vaccines commonly have positive serological test results for HIV infection, which increases their risk of being misclassified as HIV-infected, according to a report in the March 15th issue of The Journal of Infectious Diseases.
Of the 490 specimens collected from 461 uninfected vaccine recipients, the authors report, 100 (20.4%) reacted on at least 1 serologic screening test. Western blots yielded positive results on 65 of these 100 specimens of these specimens, indeterminate results on 31, and negative results on 4.

False-positive results were somewhat less likely among recipients of rgp120 subunit vaccine constructs (15.2%), the report indicates, and Western blots were indeterminate on all of these reactive specimens.

The prevalence of false-positive results was higher after vaccination with Canarypox constructs (20.7%), the researchers note, especially in patients who were boosted with rgp160.

The highest rates of false-positivity were seen among participants who received vaccinia constructs (17 of 58 serum specimens; 29.3%), the report indicates. Western blots were positive in 16 of the 17 false-positive specimens and indeterminate in 1 specimen.

With all vaccine constructs, the Genetic Systems rLAV EIA produced the largest number of reactive results.

HIV/AIDS Vaccine: Recipients at risk for false positive test results

False-Positive Serologic Tests for Human T-Cell Lymphotropic Virus Type I Among Blood Donors Following Influenza Vaccination, 1992

This one is especially interesting due to this statement:

"Conclusions.—A false diagnosis of HIV-1 infection can result from the combination of EIA and Western blot testing in blood donor and other HIV-1 screening programs."

So goes the claim that Western blot is so accurate and the "gold standard".

Results: Commercial HIV ELISA kits containing synthetic or recombinant gp120 derived polypeptides yield a higher false positive rate (range up to 25%) than HIV assay kits that lack rgp120 derived polypeptides (range up to 3%).

Hardly a 99% accuracy rate as being claimed any way you want to look at it. And this study did not take in to consideration serological cross reactivity and other factors yielding false positives. If these are taken in to account then the accuracy drops significantly further.

JAMA. 1989 Dec 22-29;262(24):3435-8.

Comment in:
·    JAMA. 1989 Dec 22-29;262(24):3465-6.

Reporting the results of human immunodeficiency virus testing.

Benenson AS, Peddecord M, Hofherr LK, Ascher MS, Taylor RN, Hearn TL.

School of Public Health, San Diego State University, CA 92182-0405.

We conducted a pilot study of potential sources of incorrect laboratory reports of human immunodeficiency virus type 1 testing using blind proficiency testing. Sets of three serum samples, including one serum sample with negative reactions in antibody tests, one serum sample with positive reactions, and one that gave false-positive results with certain testing kits, were sent as routine patient specimens to testing laboratories. Half the laboratories reported the serum sample positive for human immunodeficiency virus antibodies as "indeterminate"; one laboratory rendered a final positive report without supplemental testing. On the report forms, the actual laboratory results were often obscured and intermingled with information, sometimes incorrect, such as identifying the agent as "HTLV-III" (human T-cell lymphotropic virus type III) and advising that a test with positive results is evidence of exposure to the virus. Many of these reports have the potential to confuse, rather than to enlighten, the requesting physician.

Przegl Dermatol. 1989 Jul-Aug;76(4):308-12.

[Difficulties in serological diagnosis of HIV infection]

[Article in Polish]

Weyman-Rzucidlo D, Seliborska Z, Gluska T.

Using Abbott's kits for immunoenzymatic diagnosis of antibodies to the recombinant antigens of the HIV-1 retrovirus (EIA-II test which was higher valued than the EIA-I test of the previous generation of the same production) 16,480 examinations of the sera of high risk groups and foreign students were done. All positive or doubtful results of the EIA test were verified by the Western blot technique. The obtained results positive and doubtful are presented, and only four were not in agreement by both methods. Attention is called to the possibility of erroneous results of tests when the instructions of the producer are not followed, if the sera are incorrectly prepared for the test, and if inactivated sera are used.


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