Peripheral blood eosinophilia as a marker of acute cellular rejection in lung transplant recipients

Previous studies in solid organ transplantation have shown a relationship between circulating eosinophil (EOS) counts and the presence of acute cellular rejection (ACR). However, the relationship between this potential biomarker and ACR in lung transplant (LTx) patients remains unclear. To assess the association between EOS and the presence of acute cellular rejection in lung transplant recipients. Retrospective study of 583 transbronchial biopsies (TBB) performed in 256 lung transplant patients between 2012 and 2018. We analyzed age, sex, underlying pathology, date of transplant, indications for TBB, presence and degree of ACR, and the simultaneous absolute and relative EOS. ACR were observed in 170 of 583 TBB (29.2%). EOS in patients with ACR were higher than in patients without ACR (203.6 ± 248/mm3 vs 103.1 ± 153/mm3; p < 0.001). High levels of both absolute and relative EOS were associated with the presence of ACR regardless of the underlying disease (odds ratio [OR] 1.003; 95% confidence interval [CI], 1.002-1.004; OR 1.226; 95% CI, 1.120-1.342) and time after transplant (OR 1.003; 95% CI, 1.002-1.004 and OR 1.239; 95% CI, 1.132-1.356). Moreover, both absolute and relative EOS were strongly associated with moderate and severe grades of ACR (OR 3.55; 95% CI, 3.00-4.10 and OR 3.56; 95% CI, 3.00-4.12). EOS are elevated in ACR, especially in moderate or severe ACR. Increased vigilance for ACR is therefore advisable in lung transplant recipients with elevated EOS.