Based on the s‐IgA measurements in patients who remained free of colonization or infection compared with patients with a change in lung infection status, we constructed a statistical model such that for a given value of s‐IgA against St‐Ag in saliva, it can predict the probability of a change (worsening) in lung infection status within the next 8.5 months (median): p = 1 / (1 + exp(−(−0.9582 + 1.6518*IgA)). The gene discussed is CD79A; the disease is infection.