Risk factors for disease-related deterioration following diagnostic bronchoalveolar lavage procedures in diffuse lung disease: a case-control study

Patients

As a case–control study, we retrospectively included consecutive patients with diffuse lung disease who underwent a diagnostic BAL procedure in Oita University Hospital, Yufu, Japan, from April 2012 to November 2017, and then patients were divided into the case group who met the BAL-DDs criteria (defined later) or the control group who did not meet the criteria. Since no reports of BAL-DDs have been described in patients who only show lymph node enlargement, such as sarcoidosis without consolidation or ground-grass attenuation in the lung fields, we excluded these cases. Cases in which BAL was performed for treatment (e.g., pulmonary alveolar proteinosis) were also excluded.

The study protocol was approved by the institutional ethics committee (approval number, 1507; approval date, October 12, 2018). The need for informed consent was waived because of the retrospective nature of the study, and information on this study was posted at the hospital with a method to opt out on our web page (https://www.med.oita-u.ac.jp/naika2/for_patients/pdf/04.pdf).

The procedure, processing and analysis of BAL

BAL and the analysis including cell counts were performed by professional physicians certified by the Japan Society for Respiratory Endoscopy in Oita University Hospital as described previously (Sakamoto et al., 2004). After local anesthesia with 4% lidocaine, the patient was premedicated intramuscularly with pethidine hydrochloride (17.5–35 mg). A flexible bronchoscope (BF-260, Olympus, Tokyo) was wedged into the selected bronchopulmonary segment, typically in the middle or lingular lobe for lavage. A 50-mL sterile physiological saline solution at body temperature was instilled through the bronchoscope, and the fluid was immediately retrieved by gentle suction at a reduced pump pressure. Saline instillation was performed two or three times, resulting in 100 or 150 ml in total. The collected BAL fluid was immediately processed, filtered through gauze, and centrifuged at 550 rpm for 5 min. The total cells were counted in a hemocytometer. The slides were stained with May-Grunwald-Giemsa stain, and 900 cells were counted for the cell differentials with microscope objective lens of 40 × or 100 ×.

Outcomes and definitions

The term “BAL-AE” is rarely used in patients with non-IPF diffuse lung disease because “AE” was defined as deterioration in patients with IPF. It is difficult to clarify whether the worsening that occurred in AE was similar to that observed in IPF or whether it was a disease-related clinical deterioration in patients with non-IPF. We used the term BAL-DDs as the outcome in this study, defined according to the 2004 criteria for AE in IPF (Collard et al., 2007) and the new diagnostic criteria of International Working Group Report on AE of IPF, which were reported in 2016 (Collard et al., 2016). BAL-DD was defined as the case that met all of the following items: (1) worsening of dyspnea within one month after BAL; (2) emergence of new ground-glass opacities or consolidation within one month after BAL; (3) oxygenation deterioration with a decline of ≥10 mmHg in the partial pressure of oxygen in the arterial blood (PaO₂) from the level right before BAL; and (4) no clinical evidence of congestive heart failure, pneumothorax, pleural effusion and pulmonary embolism as a cause of the acute worsening of the patient’s condition. The control case was defined as the case that did not meet the above-mentioned the BAL-DD criteria.

In this study, in addition to one-point patient’s characteristics right before BAL, the clinical course within one month before the BAL procedure was also documented because physicians often need to make difficult decisions whether BAL should be performed for a patient taking a progressive clinical course. We defined the progressive case before BAL as a patient who met all of the following items: (1) worsening of dyspnea within one month before BAL; (2) emergence of new ground-glass opacities or consolidation within one month before BAL; (3) oxygenation deterioration with a decline of ≥10 mmHg in the partial pressure of oxygen in the arterial blood (PaO₂) from the previous level within one month; and (4) no clinical evidence of congestive heart failure, pneumothorax, pleural effusion, and pulmonary embolism as a cause of the acute worsening of the patient’s condition.

Data collection

We collected the following patient information and clinical data from medical records within two weeks before BAL: sex, age, final diagnosis, physical activity level, body temperature, desaturation on exertion according to 6-min walking test or clinical notes, serum CRP levels, Krebs von den Lungen-6 (KL-6) as a marker for the activity of interstitial pneumonia, and PaO₂, vital capacity (VC), %VC, FVC, %FVC, forced expiratory volume in one s (FEV₁), FEV1% and percentage of the diffusing capacity of the lung carbon monoxide (DL_CO) on a respiratory function test before the BAL procedure. The physical activity level was assessed according to the Eastern Cooperative Oncology Group performance status (PS) (Oken et al., 1982). The regular use of glucocorticoid, immunosuppressant and antifibrotic agent for underlying diseases before the BAL procedure was also assessed.

The high-resolution computed tomography (HRCT) findings before the BAL procedure were evaluated for signs of ground-glass opacity, consolidation, honeycombing, bronchiectasis, and emphysema. To differentiate infiltration and ground-glass opacity by the BAL procedure itself from those by DDs, newly developed lung involvements in segments other than the segment that normal saline was injected for BAL were defined as DD-consistent findings. Two respiratory physicians (YU and KK) independently reviewed the chest HRCT features. Any disagreement between the presence of the findings and HRCT diagnosis in each case was resolved by a review conducted by the same two physicians to reach a consensus. The extension of ground-glass opacity and consolidation was also evaluated.

The following information from the BAL procedure was also documented: collection rate, total cell concentration, and cellular constituents including the numbers of macrophages, lymphocytes, neutrophils and eosinophils. Furthermore, in patients with BAL-DDs, a detailed clinical information, including the timing of the BAL-DD, treatment regimen, and outcome, was collected to clarify their prognosis after the BAL-DD.

Statistical analyses

The odds ratio of each variable for BAL-DD was analyzed using a logistic regression in two models including or excluding the progressive cases before BAL. The Mann–Whitney U-test was used to compare the eosinophil counts between independent two groups because of non-normal distribution resulted from small number of patients. Two-tailed analyses were performed, and P values < 0.05 were considered statistically significant. All statistical analyses were performed using the IBM SPSS statistics software program (version 22; IBM SPSS, Tokyo, Japan).

Patients’ characteristics

A total of 498 BAL procedures were performed in the study period, and we excluded 68 patients who had only lymph node enlargement and one who underwent BAL as treatment for pulmonary alveolar proteinosis. Thus, we finally included 429 patients: IPF in 12 and non-IPF in 417 patients. Fourteen (3.3%) of 429 patients developed BAL-DD (Fig. 1). When the patients who followed a progressive clinical course before BAL were excluded, the incident rate of BAL-DD was 2.1% (8/380). None of the patients with IPF experienced BAL-AE in this study.

In the analyses including the patients who followed a progressive clinical course before BAL, the BAL-DD group had a significantly poorer PS, higher body temperature and CRP level, lower PaO₂, and a greater number of cases with desaturation on exertion and following a progressive clinical course before the BAL than the non-BAL-DD group (Table 1). No significant differences in the age, gender, KL-6 level, proportion of body temperature ≥ 38 °C, other respiratory functional parameters or regular use of glucocorticoid, immunosuppressant and antifibrotic agent for underlying diseases before BAL procedure were noted between these two groups. The extension of consolidation and ground-glass opacity was seen in the BAL-DD group significantly more frequently than in the non-BAL-DD group. Moreover, the incidence proportion of honeycombing, bronchiectasis, and emphysematous changes in the two groups did not differ significantly.

When the patients who followed a progressive clinical course before BAL were excluded, the BAL-DD group had a significantly poorer PS, higher CRP level, and greater number of cases with desaturation on exertion than the non-BAL-DD group (Table 2). The extension of consolidation and ground-glass opacity was seen in the BAL-DD group significantly more frequently than in the non-BAL-DD group. Moreover, the incidence proportion of honeycombing, bronchiectasis, and emphysematous changes in the two groups did not differ significantly as well as the analysis including the patients who followed a progressive clinical course before BAL.

BAL fluid analyses

The collection rates in the BAL-DD and non-BAL-DD groups were quite similar, as shown in Table 3. The total cell concentration and number of eosinophils were significantly higher in the BAL-DD group than in the non-BAL-DD group. However, these significances were lost when the patients who followed a progressive clinical course before BAL were excluded.

The final diagnosis of diffuse lung disease

BAL was most frequently performed in patients diagnosed with unclassified interstitial pneumonia, followed by those diagnosed with sarcoidosis, CTD-ILDs, and organizing pneumonia (Table 4). Patients with eosinophilic pneumonia (4/15, 26.7%), CTD-ILDs (4/64, 6.3%), drug-induced interstitial pneumonia (1/17, 5.9%), infection (1/21, 4.8%), hypersensitivity pneumonia (1/23, 4.3%), and unclassified interstitial pneumonia (1/107, 0.9%) suffered from BAL-DDs. On the other hand, BAL-DDs did not occur in patients with IPF, organizing pneumonia, sarcoidosis, or lymphoproliferative disease. When the progressive cases before BAL were excluded, patients with eosinophilic pneumonia (2/10, 20.0%), infection (1/17, 5.9%), CTD-ILDs (2/58, 3.4%), and unclassified interstitial pneumonia (1/103, 1.0%) suffered from BAL-DDs. The diagnosis of eosinophilic pneumonia was significantly associated with BAL-DDs whether the progressive cases before BAL were included or excluded, as shown in Table 4.

Among 15 patients with eosinophilic pneumonia, 3 and 12 were diagnosed with acute and chronic eosinophilic pneumonia, respectively. The eosinophil counts in these two types of eosinophilic pneumonia were not statistically different (median, 4.22 vs. 1.45 × 10⁵ cells/mL, p = 0.225). Furthermore, no significant difference in the eosinophil counts was noted between the patients with eosinophilic pneumonia who developed DD (n = 4) and those who did not (n = 11) (median, 2.01 vs. 1.52 × 10⁵ cells/mL, p = 0.839).

Details of the patients with BAL-DDs

Thirteen of the 14 patients with BAL-DDs experienced DDs within 10 days after the BAL procedure (Table 5). All patients with BAL-DDs received intensive treatment with high-dose systemic corticosteroids and broad-spectrum antibiotics. Consequently, 12 patients improved and were discharged from the hospital; however, two died due to progressive respiratory failure. The diagnoses of the two fatal cases were chronic hypersensitivity pneumonia and infection. In the former case, HRCT showed a reticular shadow in both lungs, and the serum was positive for antibody to Trichosporon asahi, which causes chronic summer-type hypersensitive pneumonia (Huang et al., 2006). After CTD-ILDs and drug-induced pneumonia were ruled out, the patient was diagnosed with chronic hypersensitivity pneumonia based on compatible radiological features. Two days after the BAL procedure, the oxygenation status had deteriorated, and the chest HRCT features had worsened (Figs. 2A and 2B). Despite intensive treatments with systemic glucocorticoids and antibiotics, the patients died of respiratory failure one month after the BAL procedure. The latter case showed extensive consolidation in the left lower lobe on HRCT and was admitted. Since antibiotic administration was not effective, we performed the BAL procedure at the superior lingular segment. The patient’s respiratory condition rapidly worsened seven days after the procedure. Despite the administration of systemic glucocorticoids with wide-spectrum antibiotics under mechanical ventilation, the patient died of respiratory failure three weeks after the BAL procedure. The autopsy revealed multiple pathological features, including bronchopneumonia, organizing pneumonia, diffuse alveolar damage, pulmonary hemorrhaging, and edema. No significant differences in the clinical signs, laboratory data, or HRCT features before and after BAL were noted between the patients who died and those who survived in the BAL-DD cases. However, chronic hypersensitivity pneumonia and infection with evidence of Haemophilus influenzae and Streptococcus pneumoniae isolation from sputum as the final diagnosis were only seen in the patients who died (Figs. 3A and 3B).