High neutrophils and low lymphocytes percentages in bronchoalveolar lavage fluid are prognostic factors of higher in-hospital mortality in diffuse alveolar hemorrhage

We conducted a retrospective cohort study in our hospital. The study was approved by the ethics committee of Osaka Police Hospital (Osaka, Japan) and the medical records of patients admitted between October 2008 and July 2020 were reviewed. If a patient had been admitted due to DAH two or more times during this period, only the first admission was included in the analysis. In this study, DAH was defined by the following criteria: (1) Clinical and radiological presentation that was compatible with a diagnosis of DAH, and (2) BALF that was macroscopically bloody or cytologically contained hemosiderin-burden macrophages. The exclusion criteria were as follows: (1) Hemorrhage of bronchial origin, (2) BALF findings incompatible with DAH, and (3) Lack of BALF cell-pattern data. All patients who met the inclusion criteria but not exclusion criteria were included in the analysis.

Variables included demographic data, past medical history, use of antiplatelet or anticoagulant drugs, clinical and biological findings on admission, and treatment regimens. We categorized DAH depending on the use of AT following the classification in a previous study; DAH-AT was defined as DAH that had occurred during AT and DAH-NAT as DAH that had occurred without AT [9]. Then, as in the previous study, we classified DAH-AT depending on the presence of other causes of DAH; simple DAH-AT was defined as DAH-AT with no other causes, and complicated DAH-AT as DAH-AT with etiologies other than AT [9]. Infection was confirmed when the specific microorganism was identified by culture or serological test. Considering serological findings, radiological findings and clinical courses, we clinically diagnosed immune-related disease, drug-induced pneumonitis, heart failure, and other diseases as causes of DAH. Idiopathic DAH was defined as no detection of etiological disease of DAH.

The primary outcome was in-hospital mortality. The secondary outcome was the occurrence of complications accompanied by discontinuation of AT.

The patients’ backgrounds and clinical characteristics on admission were compared between the survival and in-hospital death groups. These data were described as medians and interquartile ranges for quantitative variables and as counts and percentages for qualitative variables. We conducted the Mann–Whitney U test to compare continuous valuables, and Fisher's exact test to compare the proportions of categorical variables between the groups. Univariate logistic regressions were performed for the following two types of selected variables: 1) variables with p-values < 0.10 in the comparisons between the in-hospital death and survival groups, and 2) arbitrarily pre-defined variables that had already been proven as prognostic factors in the multivariate analyses in previous studies [2, 3, 5, 9]. The results were described as odds ratios (ORs) and 95% confidence intervals (CIs). We defined 60 mL/min and twice the upper limit of normal as the cutoff values of the estimated glomerular filtration rate (eGFR) and lactate dehydrogenase, respectively, as used in a previous study [2]. For the other variables, the cutoff values were determined as those that maximized the sensitivity plus specificity total in the receiver operating characteristic curve (ROC). At the same time, the area under the curve (AUC) for each ROC was calculated. Then, we compared in-hospital mortality between four groups divided according to neutrophils and lymphocytes percentages in BALF; patients with high neutrophils and lymphocytes, patients with high neutrophils and low lymphocytes, patients with low neutrophils and high lymphocytes, and patients with low neutrophils and lymphocytes. The cutoff values of neutrophils and lymphocytes percentage in BALF were same as above. We analyzed with Fisher's exact test and Bonferroni correction. Finally, we compared in-hospital mortality and the BALF cell pattern between DAH-AT and DAH-NAT, and then between complicated DAH-AT and simple DAH-AT. The threshold for significance was p < 0.05. All statistical analyses were performed in EZR software (Saitama Medical Center, Jichi Medical University, Saitama, Japan), which is a graphical user interface for R (The R Foundation for Statistical Computing, Vienna, Austria) [11].

During the study period, 147 patients were suspected of having DAH. However, 79 patients were excluded for the following reasons: bronchoscopy was not performed (n = 59), hemorrhage from bronchial origin was responsible for the symptoms (n = 3), BALF findings were not compatible with DAH (n = 2), and the data of the BALF cell pattern were not obtained (n = 15). Consequently, 68 patients were included in our analysis (Fig. 1). The backgrounds of patients are shown in Table 1. The median age was 75 (72–80) years, and 49 (72%) patients were male. Forty-eight (71%) patients were receiving AT; 7 (10%) received antiplatelet therapy alone, 23 (34%) received anticoagulant therapy alone, and 18 (26%) received both antiplatelet and anticoagulant therapies. The etiological diseases of DAH were immune disease (8.8%), infection (13%), drug-induced pneumonitis (5.9%), heart failure (4.4%), other disease (13%), and idiopathic (54%). No variable was significantly different between the survival and death groups. The clinical characteristics of patients on admission are displayed in Table 2. Forty-seven (69%) patients received invasive or noninvasive mechanical ventilation. Fifty-six (82%) patients were administered corticosteroids. Neutrophils and lymphocytes percentages in BALF, and eGFR were significantly different between the survival and death groups.

Eighteen (26.5%) patients died due to DAH in our hospital. The cutoff values for oxygen flow (4 L/min) and neutrophils (44.5%) and lymphocytes percentages (14%) in BAL were determined by the ROC curves (Additional file 2: Fig. S1). Univariate analysis of factors associated with in-hospital death are presented in Table 3. The variables significantly associated with in-hospital death were neutrophils percentage in BALF ≥ 44.5% (OR 11.4, 95% CI 3.38–38.5), lymphocytes percentage in BALF < 14% (OR 6.37, 95% CI 1.97–20.6), idiopathic DAH (OR 0.31, 95%CI 0.10–0.95), oxygen flow ≥ 4L/min (OR 3.90, 95%CI 1.20–12.6), and eGFR < 60 mL/min (OR 5.00, 95%CI 1.29–19.4). In-hospital mortality was significantly higher in patients with neutrophils percentage ≥ 44.5% and lymphocytes percentage < 14% compared with patients with neutrophils percentage < 44.5% and lymphocytes percentage ≥ 14% (Additional file 1: Table S1).

Figure 2 shows the numbers of patients and their etiological diseases of complicated DAH-AT, simple DAH, and DAH-NAT. In-hospital mortality was not significantly different between DAH-AT and DAH-NAT (Additional file 1: Table S2). However, showed in-hospital mortality was significantly worse in complicated DAH-AT compared with simple DAH-AT (Additional file 1: Table S3). Regarding the BALF cell pattern, the percentage of neutrophils was significantly higher in complicated DAH-AT than in simple DAH-AT.

An 80-year-old woman experienced stroke as a complication following discontinuation of AT. She had been administered aspirin for angina pectoris and warfarin for atrial fibrillation. She discontinued these medicines on the day of admission, and then was diagnosed as having experienced an insular cortex stroke 15 days after discontinuation, which caused higher brain dysfunction, but was not critical.