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It will generally not be positive during the 4–6 week incubation period before the onset of symptoms. The highest amount of heterophile antibodies occurs 2 to 5 weeks after the onset of symptoms. [9] If positive, it will remain so for at least six weeks. [10] An elevated heterophile antibody level may persist up to 1 year. [9]
Heterophile antibodies are IgM antibodies with affinity for sheep and horse red blood cells. They appear during the first week of infectious mononucleosis symptoms, 3–4 weeks after infection and return to undetectable levels 3 to 6 months after infection. Heterophile antibody is a fairly specific but insensitive test for EBV.
The heterophile antibody test, or monospot test, works by agglutination of red blood cells from guinea pigs, sheep and horses. This test is specific but not particularly sensitive (with a false-negative rate of as high as 25% in the first week, 5–10% in the second, and 5% in the third). [26]
The antibody that fails to react is known as the blocking antibody and prevents the precipitating antibody from binding to the antigens. Thus the proper precipitation reaction does not take place. However, when the serum is diluted, the blocking antibody is as well and its concentration decreases enough for the proper precipitation reaction to ...
An example of helpful cross-reactivity is in heterophile antibody tests, which detect Epstein-Barr virus using antibodies with specificity for other antigens. Cross-reactivity is also a commonly evaluated parameter for the validation of immune and protein binding based assays such as ELISA and RIA .
She spent eight years on dialysis before doctors concluded she’d likely never get a donated organ – she’d developed super-high levels of antibodies abnormally primed to attack another human kidney. So Looney, 53, sought out the pig experiment. No one knew how it would work in someone “highly sensitized” with those overactive antibodies.
Rapid tests procurable at a consumer level often fail to detect antibody until at least three months have passed since the initial infection. [26] It takes longer for fingerstick blood or other fluids to accumulate sufficiently high levels of antibodies compared to venous blood plasma sampling.
Serostatus refers to the presence or absence of a serological marker in the blood. The presence of detectable levels of a specific marker within the serum is considered seropositivity , while the absence of such levels is considered seronegativity .