Removal · field guidance

Why IgM should not be used after 30 days

Persistent IgM positivity beyond a month is usually a false positive, so CDC recommends ignoring IgM in late-disease testing.

Steps

schema.org/HowTo

01
IgM is a short-lived antibody class normally produced in the first weeks of infection.
02
After 30 days, true IgM levels typically fall while IgG persists.
03
Standalone IgM positivity in late disease most often reflects cross-reactivity or polyclonal activation.
04
Per CDC, do not consider IgM alone diagnostic if symptoms have lasted more than a month.
05
Use IgG band criteria instead for late-stage testing.

loading…