Pertussis labs collected 6 wk into resp infx showed iga & igg pt/fha +. igm pt equiv/fha neg. no tdap booster x > 10 yr. could it be recent illness?

Probably : You'd expect igg & igm to go up after primary immunization (which wanes). Iga and igg to pt are more specific for the diagnosis of b. Pertussis. Culture & pcr are better but not 6 weeks out (though pcr might still be +ve).

Not likely: If this were closer to the start of the respiratory infection, i would say this is just representative of immunity; however, with 6 weeks or more since the start, it may be a sign of conversion from igm -> igg (though you would expect at least some igm level still). Iga is associated with exposure to pathogen, but there is a high seroprevalence in adults with pertussis iga, without evidence of...