Initial testing with a CBC--looking for atypical lymphocytes (which after several days replace the early granulocytic response) and a heterophile antibody
titer--is a reasonable strategy.
When the mononucleosis is on its way toward resolution, the heterophile antibody
and the IgM VCA may be positive or negative, IgG VCA will be positive (and will remain so for life), but EBNA still will be negative.
To avoid this, serum specimens should be mixed with staphylococcal protein A to adsorb the rheumatoid factor--an unnecessary complication with the existence of the heterophile antibody
Mononucleosis has, however, been associated with a large number of antibodies (in addition to the commonly measured heterophile antibody
), including cold agglutinins, as well as with cryoglobulinemia.
Moreover, children younger than 8 years are less likely to ever produce heterophile antibody
, so the test isn't useful in that age group.
(Many physicians would look at the negative heterophile antibody
result in conjunction with a complete blood count report and reassess their differential diagnosis.) A better way to achieve substantial cost savings would be to implement a clinical algorithm to differentiate IM and IM-like diseases from other diseases and use it in conjunction with the testing algorithm.
"Question #1: For tests that do not include built-in positive and negative controls, are known positive and negative controls tested on each day of analysis for all qualitative or semi-quantitative antigen/antibody tests (e.g., rheumatoid factor, rapid plasma reagin, ASO, hCG, heterophile antibody
In addition, a control group that consisted of a selection of 50 patients from the 1689 original patients who were heterophile antibody
negative but who had a normal lymphocyte count and generated no atypical lymphocyte flag were also tested for EBV IgM antibodies.
To determine if the discrepant results were caused by heterophile antibody
interference, we added 500 [micro]L of patient sample (n = 11) to a Scantibodies Laboratory Heterophilic Blocking Tube (HBT) and incubated the tube for 1 h before measuring 25-hydroxyvitamin D on the LIAISON instrument.
Although the heterophile antibody
test may occasionally be false positive in patients with autoimmune diseases, serum sickness, pregnancy, or HIV infection, false negatives are far more frequent (about 15% overall), particularly in children who are under 4 years of age (approximately 45%).
Protein regions within the cTnI molecule that are susceptible to the modifications noted above--as well as the variable nature of epitope-dependent heparin (4), heterophile antibody
(5), and autoantibody (6) binding--are likely to exhibit variable immunoreactivity and even loss of reactivity in some cases.
On the Roche cTnT platform, 10 samples (0.56%) were classified as outliers, and no heterophile antibody
interference was identified with this assay.