C4A and infection: In the subgroup analyses no difference in C4 deficiency was observed between male NTM and male control patients (7/14 [50%] vs 28/49 [57%], OR = 0.75, 95% CI = 0.23–2.47, p = 0.045) The subgroup analyses were justified as the Breslow-Day test found evidence of interaction between sex and infection (NTM vs. Healthy) with respect to type of deficiency (p = 0.108 for C4B<2 and p = 0.045 for C4Aor C4B<2).