yep - babesia testing hit and miss
the antibodies can be positive or negative for a number of reasons - and the IFA can be negative when the antibodies are positive.
there are numerous reasons -
-very small numbers of infected cells in the blood - making direct methods v low sensitivity
-many species and strains - reagents used in antibody tests may only detect 1-2 strains
have a look at this page where he covers babesia testing
its a little unexpected that one antibody-based test is negative and the other positive - perhaps the different labs use different antigens for their tests or set different thresholds for positive?
however i would assume the positive result is accurate - as with antibody tests as with most co-infection tests its sensitivity is the main issue (detecting it when it is in fact there) - rather than false positives ( reporting an infection when there is none) - so a positive result is generally pretty reliable - whereas negative results are common - even in infected people.
typically coinfection tests might be only 25-50% sensitive - but 80-95% specific (so if you get a positive results it typically a 90% chance you are indeed infected - even if you have other negative results)
Post Edited (Garzie) : 3/23/2021 9:54:06 AM (GMT-6)