Feasibility of sputum induction in lung transplant recipients

Sputum induction (SI) is nowadays being applied as a non-invasive and safe method to investigate airway inflammation in pulmonary diseases. We investigated the feasibility of SI after lung transplantation (LTX), and compared sputum and bronchoalveolar lavage (BAL) cellular characteristics and interleukin-8 (IL-8) levels. Results were also compared with 11 healthy subjects. SI as performed between 26 and 1947 d after LTX in 19 recipients, was successful in 16 of 22 attempts (73%). Six patients failed to produce sputum after induction, mostly just post-LTX and with having a lower forced expiratory volume in 1 s (FEV1). The success rate in clinically stable patients after the first month post-LTX was 93%. Side-effects were absent. Sputum recovery, viability and squamous cell contamination were comparable between LTX patients and healthy subjects. In the LTX group, total cell counts, neutrophil percentages and IL-8 levels were much higher in SI than BAL (1.6 x 10(6)/mL, 65.5% and 54.2 ng/mL vs. 0.1 x 10(6)/mL, 3.0% and 0.01 ng/mL; p < 0.001). Although LTX-neutrophil percentages in SI and BAL correlated properly (rho=0.72, p=0.04), both techniques are not interchangeable. We conclude that sputum induction is feasible, well tolerated, and without major side-effects in stable patients after the first month post-LTX. Induced sputum may be a useful tool to study inflammatory changes of the airways after LTX, and because of the large quantity of neutrophils sampled, especially for further studies on the pathogenesis of bronchiolitis obliterans.