F2 and chronic obstructive pulmonary disease: Following a case–control study comparing the seroprevalence of B. pertussis in 90 patients with COPD with an equal number of control patients without COPD, Hashemi et al.33 reported no significant association between COPD and anti-pertussis toxin (PT) IgA seropositivity (p = 0.448), indicative of recent infection.