@halcyon
I've been having more brain fog over the last few days, so I am struggling to understand things. But in terms of the operation of the complement fixation test (CFT), I don't think this depends on having microbial antigens present in the patient's blood. I think antigens from the microbe you are testing for are obtained from an external source, and then added to the patient's blood sample, so that these antigens will attach to the patient's antibodies (if present), which is then the cue for the complement to attach itself to the antigen-antibody complex. I
read that complement will attach itself to almost any antigen-antibody complex.
So as far as I can see, having low levels of enterovirus and its antigens in the blood would not stop the CFT from working. There are a few tutorial introductions to the complement fixation test
here,
here and
here.
Certainly though Dr Chia never mentions the complement fixation test in his
list of testing methods useful for detecting chronic enterovirus infections, so presumably he considers the CFT to be too insensitive for chronic enterovirus infections.
He does not mention the ELISA either, so guess the sensitivity of that for chronic enterovirus may also be less than adequate.
I came across
this study which compared CFT and ELISA testing sensitivity in coxsackievirus B1 infections, which found that the CFT is less sensitive than the ELISA:
The sensitivity is clearly related to the time when serum samples are taken.
When serum samples are taken within 3 days after the onset of symptoms, the sensitivity is low (5 of 22 [23%]). When serum is drawn later than 3 days after onset, the sensitivity is good (20 of 24 [83%]).
The CFT with the antigen mixture is less sensitive than the ELISA (44% versus 81%)
In the first few days of acute coxsackievirus B infection, the study found that CFT was more sensitive than ELISA. But after that, ELISA is the more sensitive.
So I should think that for chronic enterovirus antibody testing:
Microneutralization sensitivity > ELISA sensitivity > CFT sensitivity.
If you look at
@Emootje's two enterovirus test results posted
earlier in this thread, these were done at European labs: the
first test at a
Belgium lab, and the
second test in a
Dutch lab, both tests showing elevated CVB3 antibody titers. The second test looks like it is a neutralization test (not sure about the first — would you know,
@Emootje?).
One type of neutralization test is a
plaque reduction neutralization test (PRNT). A micro-neutralization test is another type, and similar to PRNT.
My own coxsackievirus B and echovirus CFT tests that I had done in the UK were negative, but that may just be down to the insensitivity of the CFT for chronic enterovirus infections.
Enterovirus is probably the most important virus to test for in ME/CFS, yet I get the impression only a few patients on this forum have been properly tested for this virus, using appropriately sensitive lab tests like neutralization. Presumably this is down to cost factors (the two ARUP Lab micro-neutralization tests for coxsackievirus B and echovirus costs around $500 each), or possibly because insurance does not cover these ARUP tests.
It would be good if we could find some labs that offer a neutralization / micro-neutralization test for coxsackievirus B and echovirus at more reasonable prices.
Perhaps the
Dutch lab, the University Medical Center (UMC) Utrecht, might be one good lab that ME/CFS patients might use.
@Emootje, do you remember how much the UMC coxsackievirus B neutralization test cost?
There may be other labs in the Europe which do coxsackievirus B and echovirus neutralization testing. It would be a case of Google searching in different languages in order to find them.