Febrile neutropenia was consistently reduced in all three groups where data were available: BTKi + anti-CD20 vs another comparator (RR 0.41, 95% CI:0.29–0.59, I2 = 38%; 5 trials), BTKi + venetoclax vs another comparator (RR 0.18, 95% CI: 0.08–0.40, I2 = 41%; 3 trials), and BTKi monotherapy vs another comparator (RR 0.32, 95% CI:0.18–0.59, I2 = 7%; 5 trials) (Fig. 8A–B). The gene discussed is IBTK; the disease is Decreased total neutrophil count.