Disclaimer:
I am here as a highly medically interested person looking for an explanation of an observed phenomenon, not for medical advice, as it is not about my person.
I work in a diagnostic laboratory and have seen several blood tests where a phenomenon occurs that is inexplicable to me. Some patients test IgG negative but IgM positive for Borrelia. So far, so unspectacular, since IgM antibodies are signs of an early stage of infection, whereas IgM antibodies usually tend to appear in later stages. As a rule, these patients are then advised by the treating physician to repeat the blood test a few weeks later. Now, in my opinion, IgG antibodies should also be found. However, I have already had several cases in which no IgG antibodies were detected even 6 months after the initial findings, but the IgM tests were unchanged.
In addition, I noticed that the findings were partly contradictory. For example, I recently saw a patient test positive for anti-OspC B. spielmanii, anti-OspC B. garinii, anti-OspC B. burdorferi, and anti-OspC B. afzelii, while the anti-p41 and anti-VlsE B. burdorferi tests were negative.
According to this and this, p41 is specific for B. afzelii and B. garinii. So a person who tests positive for these two types of Borrelia should also be positive for p41, right? Similarly, I am perplexed that the test for p39 in this person is equivocal, although p39 is actually a highly specific protein for Borrelia and I would expect a positive finding for p39 if a patient tests positive for four species of Borrelia.
I should also mention that the blood count has not changed in the last six months. Except for Anti-OspC B. garinii, all positive findings were determined positive again and the negative results were also confirmed as negative again.
| Analysis | Result (now) | Result (6 months ago) | Result (1 year ago) |
|---|---|---|---|
| Borrelia IgG | - | - | - |
| Borrelia IgM (LIA) | + | + | + |
| Borrelia IgM confirmation (Western Blot) | + | + | - |
| Anti-OspC B. spielmanii | + | + | / |
| Anti-OspC B. garinii | +- | + | / |
| Anti-OspC B. burdorferi | + | + | / |
| Anti-OspC B. afzelii | + | + | / |
| Anti-p39 | +- | +- | / |
| Anti-p41 | - | - | / |
| Anti-VlsE B. burdorferi | - | - | / |
What do you think? Is this a case of an acute infection since half a year, where interestingly no IgG antibodies and no antibodies against p41 and VlsE are formed? Could it be, due to the contradictory results, that the person is not infected with Borrelia, but the antibodies are caused by another disease? So possibly a cross-reactivity?
This and this paper suggests, that false positives are certainly possible. I understand that a test can be false positive, after all that is what is meant by specificity.But how likely is it that the same person will get another false positive test 6 months later? I suspect that this can only happen if the person actually makes antibodies similar to the ones we are looking for. Now this still seems possible to me with a positive result, but the blood values I am questioning would, to my limited understanding, require several reproducible false positive tests at once, which would make me doubt the specificity of the tests.
I look forward to your explanations and to learning more about this exciting topic.
