The aim of this study was to evaluate the diagnostic yield for lung complication after allo-HSCT by multiple parameter system through BAL.

一) Adult patients with hematology disease under allo-HSCT at any phase of treatment are enrolled according to the following criteria:

1. lung infiltration detection at computed tomography (CT) scan.
2. Patients with fever, cough, respiratory symptoms. According to the investigators, the patients fulfilling these criteria undergo BAL as soon as possible

二) The BALF samples were tested using such methods

1. classic microbiological cultures designed for bacteria, fungi, and mycobacteria.
2. Detection of human cytomegalovirus (CMV) and EB virus in serum and BAL was tested using a Real-time PCR kit.
3. Detection of aspergillus galactomannan antigen 1,3-beta-D-glucan in serum and BAL was performed using an enzyme immunoassay method.
4. Cytological and pathogenic microscopic evaluation in BALF
5. Flow cytological analysis of T lymphocyte subsets in BALF and serum
6. Cytokine detection in BALF and serum
7. Microbiology detection in BALF by mNGS

三) Pathogenic spectrum analysis and Targeted etiological therapy

Inclusion Criteria:

1. Diagnosed with hematological diseases.
2. Recipients of allogeneic peripheral blood stem cell transplantation.
3. Lung infiltration detection at computed tomography (CT) scan.
4. Patients with fever, cough, respiratory symptoms.
5. Consent to BAL and follow-up observation after BAL

Exclusion Criteria:

1. Severe bleeding tendency, platelet less than 20000/uL, or severe coagulation dysfunction;
2. Multiple bullae are at risk of rupture;
3. Untreated patients with active pulmonary tuberculosis;
4. Patients with severe consumptive diseases or conditions and various causes can not cooperate well
5. Cardiac insufficiency, severe pulmonary ventilation dysfunction
6. Recent massive hemoptysis
7. Aortic aneurysm and esophageal varices are at risk of rupture

High morbidity and mortality in patient receiving hematopoietic Stem Cell Transplantation (HSCT) are resulted from lung complications. Diagnosis of the etiology affects the choice of treatment. The bronchoalveolar lavage (BAL) analysis is safe and widely accepted, which provide valuable information for pathogen identification in pulmonary infections diagnosis.