Abstract
Objective
To explore the clinical characteristics and independent risk factors of pneumococcal pneumonia complicated with plastic bronchitis.
Methods
156 patients with pneumococcal pneumonia who were admitted to the Department of Pediatrics of the First Affiliated Hospital of Xinxiang Medical University. The patients were divided into plastic bronchitis (PB) group and non-plastic bronchitis (non-PB) group. PB patients were further divided into complication group (EC) and non-complication group (non-EC). The Mann-Whitney U test or chi-square test was used to compare the differences between the groups. The ROC curve was drawn to evaluate the accuracy of independent risk factors in predicting PB.
Results
There were significant differences in the positive rate of pulmonary consolidation in different lobes (χ2 = 20.01, P = 0.0005), among which the probability of consolidation in the right lower lung was significantly higher than that in the other four lobes (P < 0.05). Bronchoscopy showed that the PB group was more serious than the non-PB group in terms of mucosal erythema (P = 0.02) and color of secretion(P < 0.01). The extrapulmonary complications were more common (P < 0.05). Multivariate analysis showed that mucosal erythema, secretion color and PCT were independent risk factors for PB (P < 0.05). ROC curve analysis showed that mucosal erythema, secretion volume, secretion color and PCT had a certain predictive value for PB, with AUCs of 0.7, 0.77, 0.71 and 0.61, respectively.
Conclusion
The amount of secretion, mucosal erythema, secretion color (yellow-white) and PCT are independent risk factors for plastic bronchitis and have high value in its prediction.
Keywords: Streptococcus pneumoniae, Plastic bronchitis, Bronchoscopy, CT, Children
Introduction
Plastic bronchitis (PB) is a rare obstructive airway disease characterized by the formation of thick and tough casts within the tracheobronchial tree, leading to partial or complete bronchial obstruction. In severe cases, it can cause respiratory distress and even endanger respiratory and circulatory functions. The pathophysiological mechanism of PB is not fully understood. Most reported cases occur in children, but PB is associated with a variety of clinical conditions, including congenital heart disease, asthma, lung trauma, lung transplantation, and acute respiratory tract infections. Among the respiratory infections that cause PB, pathogens include Mycoplasma pneumoniae, bocavirus, and Streptococcus pneumoniae [1].
Streptococcus pneumoniae is a common cause of bacterial pneumonia in children [2]. Streptococcus pneumoniae (S. pneumoniae) has attracted much attention due to its significant impact on respiratory health. Despite efforts to promote vaccination, infections caused by vaccine serotypes still occur [3]. Factors such as rural residence, late medical treatment, presence of danger signs, and comorbidities significantly affect the recovery time of pneumonia [4]. At the same time, antibiotic resistance is also considered to be one of the factors affecting the treatment and prognosis of Streptococcus pneumoniae. About 17% of Streptococcus pneumoniae strains are resistant to at least three different antibiotic series [5]. Recent studies on other pathogens have shown that PB can also affect the treatment effect and prognosis of pneumonia. In a study of PB caused by Mycoplasma pneumoniae infection, fever, extrapulmonary complications, pleural effusion, cough duration, and lactate dehydrogenase (LDH) levels were identified as independent risk factors for PB [6]. Fever duration, PCT, and LDH are independent risk factors for adenovirus-induced mucus plug formation [7]. X-ray findings including mediastinal emphysema and pulmonary consolidation, neutrophils, elevated aspartate aminotransferase and lactate dehydrogenase levels are risk factors for influenza virus pneumonia complicated with PB [8]. Currently, there are few studies on pneumococcal pneumonia complicated with PB, and the risk factors for PB are still not fully understood. In this retrospective study, the clinical characteristics and risk factors of pneumococcal pneumonia-induced PB were explored. By analyzing clinical data and bronchoscopic results, understanding the etiology and clinical features of pneumococcal pneumonia-induced PB can provide guidance for clinicians to optimize patient care and improve prognosis.
Research methods
Research subjects
A retrospective analysis was performed on patients with pneumonia admitted to the Department of Pediatrics of the First Affiliated Hospital of Xinxiang Medical University from December 2018 to August 2023. This study strictly followed the Declaration of Helsinki and was approved by the Ethics Committee of the First Affiliated Hospital of Xinxiang Medical University(Ethics Number: EC-023-448). Since this study was a retrospective study, informed consent was waived.
Inclusion criteria: (1) Age 1 month to 16 years; (2) Meet the diagnostic criteria for pneumonia [9]; (3) Positive pneumococcal DNA by multiplex polymerase chain reaction (PCR) test of bronchoalveolar lavage fluid or positive bacterial culture. Exclusion criteria: patients with pneumonia known to be caused by other pathogens; patients with foreign bodies in the lungs or other lung diseases; patients with any of the following diseases or conditions that may affect the study results: severe chronic diseases (such as uncontrolled cardiovascular disease, liver and kidney dysfunction, etc.), malignant tumors, active tuberculosis or other lung infectious diseases, recent (such as within the past month) antibiotic treatment for other reasons, immunodeficiency status (such as AIDS, long-term use of immunosuppressants, etc.), recent (such as within the past three months) pneumococcal vaccination; patients who are intolerant to any examination or treatment procedures required for this study; patients with incomplete clinical data or unable to provide necessary information as required by the study.
When computed tomography (CT) confirms pulmonary consolidation and atelectasis, a standardized bronchoscopy and bronchoalveolar lavage (BAL) procedure is performed [10]. PB can be diagnosed by finding bronchial obstruction with thick secretions and tree-like bronchial casts on bronchoscopy [11, 12].
Study design
Patients were divided into plastic bronchitis (PB) and non-plastic bronchitis (non-PB) groups according to the presence or absence of plastic sputum plugs under bronchoscopy. The PB group showed partial obstruction of the bronchial lumen or the presence of thick or rubbery casts. The non-PB group only showed mucosal erythema, edema, and flocculent secretions. PB patients were further divided into complications group (EC) and non-complication group (non-EC) according to the presence or absence of extrapulmonary complications. Extrapulmonary complications include cardiovascular, skin, digestive organs, respiratory system, nervous system, blood/hematopoietic system, musculoskeletal, sensory organs, and genitourinary tract manifestations [13]. Clinical data were collected after admission, including demographic characteristics, clinical manifestations (such as fever, cough, wheezing, etc.), laboratory test results (white blood cell count, neutrophil ratio, lymphocyte ratio, C-reactive protein, procalcitonin, lactate dehydrogenase, etc.), chest imaging manifestations (location and number of lobes with pulmonary consolidation), fiberoptic bronchoscopy (FOB) examination findings, length of hospital stay, extrapulmonary complications, etc.
Socio‑economic & Lifestyle Survey: Within 24 h of admission, parents or guardians completed a structured questionnaire that covered four domains: (1) passive cigarette smoke exposure (defined as ≥ 1 cohabiting smoker with daily indoor smoking); (2) incomplete pneumococcal conjugate vaccination (≤ 2 doses of PCV7/10/13 recorded in the immunization booklet); (3) under‑nutrition (WHO BMI‑for‑age Z‑score < − 2); and (4) low socio‑economic status (SES) (monthly family income < ¥5,000 or both parents’ highest educational level ≤ junior middle school). Items with < 5% missing data were imputed by multiple imputation (five iterations, chained equations).
Fiberoptic Bronchoscopy (FOB) and Bronchoalveolar lavage (BAL)
FOB examination was performed using an Olympus 3.1 mm BF-XP290 or Olympus 4.2 mm BF-P290 bronchoscope. The lavage solution was injected 3–5 times with sterile saline heated to 37 °C at a rate of 1 ml/kg/time. BAL fluid was recovered under a negative pressure of 6.65–13.3 kPa (50–100 mmHg). The observation sites included 9 sites, including the trachea, right main trunk, right upper lobe, right bronchial intermediate trunk, right middle lobe, right lower lobe, left main bronchus, left upper lobe (including lingula), and left lower lobe. The bronchi with pulmonary consolidation shown on CT were particularly observed. The visual features of the bronchoscope at each site were recorded, including the amount and color of the secretions, and whether the airway mucosa was edematous, erythematous, and pale [14]. The color of the secretions was recorded as 1 if the secretions appeared yellow or white, and 0 otherwise. The scoring criteria for the characteristics of mucosal pallor (0 = absent, 1 = present), erythema (none = 0, mild/capillary exposure = 1, severe/erythema = 2, hemorrhage/erosion = 3), mucosal edema (none = 0, mild = 1, severe = 2), and the amount of secretions (0 = absent, 1 = small, 2 = large) were as follows: 0 points indicated that no secretions were observed at any site; 1 point indicated that there were bubbly or viscous secretions filling more than 1/3 of the bronchial lumen, or less than 1/2 of the site had viscous secretions; 2 points indicated that more than 1/2 of the site had viscous secretions, or was blocked by secretions.
Statistical analysis
Statistical analysis was performed using GraphPad Prism 9.0 (GraphPad Software Inc., San Diego, CA, USA). Normally distributed continuous variables were expressed as mean ± standard deviation, and the differences between the groups were compared using t-test. Non-normally distributed variables were expressed as median (interquartile range), and the differences between the two groups were compared using Mann-Whitney U test. Categorical variables were expressed as percentages, and the differences between the two groups were compared using chi-square test, continuity correction test, or Fisher’s exact test. Spearman correlation analysis was used to analyze the correlation between PB and EC and each variable. Multivariate logistic regression analysis was used to screen independent risk factors for PB, and ROC curves were drawn to evaluate the predictive accuracy of independent risk factors for PB. Kaplan-Meier analysis was used to evaluate the effects of PB and complications on hospital stay, and the results were compared using log-rank test. P < 0.05 was considered statistically significant.
Multivariate logistic regression equation was used:
 |
X1 ~ X4 mucosal erythema, secretion color, abnormal coagulation function, and PCT.
Results
Demographic characteristics of the study population
A total of 156 patients were included in this study, including 127 males (81.41%) and 29 females (18.59%), with a median age of onset of 1.92 years; 69 patients (44.23%) were admitted to the ICU. The median medical history before admission was 6 days, the median cough duration was 5.5 days, 145 patients (92.95%) had cough symptoms, 60 patients (38.46%) had fever symptoms, and 31 patients (19.87%) had wheezing symptoms. The median length of hospital stay was 12 days [8, 15]. 42 patients (26.92%) had plastic bronchitis, and the median number of lobes with pulmonary consolidation was 1 (1.00, 2.00) (Table 1).
Table 1.
Comparison of clinical characteristics between PB and non-PB patients [n (%), IQR]
| Variable | Total | PB (n = 42) | Non-PB(n = 114) | Z/χ2 | P |
|---|---|---|---|---|---|
| Age, years old | 1.92 (0.33, 4.46) | 3.37 (0.72, 5.58) | 2.33 (1.46, 4.10) | 2.089 | 0.037 |
| Gender, Male, n (%) | 156 (100) | 29 (18.59) | 127 (81.41) | 0.125 | 0.724 |
| ICU, n (%) | 69 (44.2) | 22 (52.4) | 47 (41.2) | 1.548 | 0.213 |
| Cough,d | 5.50 (2.00, 15.00) | 5.00 (2.00, 14.75) | 2.00 (6.00, 14.75) | 0.336 | 0.736 |
| Fever, d | 0.00 (0.00, 3.00) | 0.75 (0.00, 4.75) | 0.00 (0.00, 2.00) | 1.742 | 0.082 |
| Breathing, d | 0.00 (0.00, 0.23) | 0.00 (0.00,0.00) | 0.00 (0.00, 0.44) | 1.172 | 0.241 |
| Medical history, d | 6.00 (3.00, 15.00) | 5.50 (3.00, 15.00) | 6.00 (2.25, 15.75) | 0.212 | 0.832 |
| Hospitalization days, d | 12.00 (8.00, 15.00) | 14.50 (10.25, 20.75) | 11.00 (8.00, 14.75) | 2.798 | 0.005 |
| WBC, 10^9/L | 9.63 (6.95, 13.22) | 10.18 (7.79, 12.37) | 9.10 (6.48, 13.30) | 0.973 | 0.331 |
| Neutral particle ratio | 55.35 (37.00, 79.68) | 65.05 (45.73, 84.40) | 52.40 (35.90, 72.98) | 2.178 | 0.029 |
| Lymphocyte ratio | 34.35 (17.20, 54.00) | 25.65 (12.43, 48.25) | 41.65 (20.38, 55.23) | 2.118 | 0.034 |
| CRP, mg/L | 6.40 (1.03, 21.80) | 9.39 (2.56, 75.28) | 5.65 (0.79, 17.13) | 2.268 | 0.023 |
| PCT, ng/ml | 0.30 (0.04, 0.73) | 0.62 (0.07, 4.14) | 0.24 (0.03, 0.61) | 3.054 | 0.002 |
| LDH, U/L | 285.00 (232.00, 437.25) | 362.50 (258.00, 584.00) | 268.00 (219.00, 372.75) | 2.556 | 0.011 |
| Interleukin-6, ng/ml | 7.86 (2.21, 23.77) | 21.20 (5.44, 56.61) | 6.55(0.46,15.00) | 3.686 | 0.000 |
| Number of lobes with pulmonary consolidation | 1.00 (1.00, 2.00) | 1.00 (1.00, 2.00) | 1.00 (1.00, 2.00) | 0.643 | 0.520 |
| Right upper lobe, n (%) | 35 (22.4) | 11 (26.2) | 24 (21.1) | 0.466 | 0.495 |
| Right middle lobe, n (%) | 46 (29.5) | 11 (26.2) | 35 (30.7) | 0.300 | 0.584 |
| Right lower lobe, n (%) | 66 (42.3) | 20 (47.6) | 46 (40.4) | 0.664 | 0.415 |
| Left upper lobe, n (%) | 34 (21.8) | 9 (21.4) | 25 (21.9) | 0.005 | 0.946 |
| Left lower lobe, n (%) | 39 (25.0) | 11 (26.2) | 28 (24.6) | 0.043 | 0.835 |
| Mucosal erythema, n (%) | 103 (66.0) | 36 (83.3) | 67 (58.8) | 9.932 | 0.002 |
| Mucosal edema, n (%) | 114 (73.1c) | 36 (85.7) | 78 (68.8) | 4.665 | 0.031 |
| Mucosal edema, n (%) | 73 (46.8) | 19 (45.2) | 54 (47.4) | 0.056 | 0.813 |
| Mucosal pallor, n (%) | 92 (59.0) | 38 (90.5) | 54 (47.4) | 23.573 | 0.000 |
| Secretion volume, n (%) | 114 (73.1) | 40 (95.2) | 108 (94.7) | 21.069 | 0.000 |
| Extrapulmonary complications, n (%) | 70 (44.9) | 27 (64.3) | 43(37.7) | 8.757 | 0.003 |
| Electrolyte abnormalities, n (%) | 16 (10.3) | 6 (14.3) | 10 (8.8) | 1.014 | 0.314 |
| Pleural effusion, n (%) | 21 (13.5) | 11 (26.2) | 10 (8.8) | 7.994 | 0.005 |
| Sepsis, n (%) | 20 (12.8) | 12 (28.6) | 8 (7.0) | 12.757 | 0 |
| Cardiovascular injury, n (%) | 29 (18.6) | 13 (31.0) | 16 (14.0) | 5.804 | 0.016 |
| Abnormal coagulation function, n (%) | 11 (7.1) | 9 (21.4) | 2 (1.8) | 18.126 | 0 |
| Anemia, n (%) | 29 (18,6) | 8 (19.0) | 21 (18.4) | 0.008 | 0.929 |
| Liver damage, n (%) | 20 (12.8) | 11 (26.2) | 9 (7.9) | 9.192 | 0.002 |
| Renal injury, n (%) | 4 (2.6) | 4 (9.5) | 0 (0.0) | 11.143 | 0.001 |
Comparison of clinical characteristics between PB and non-PB patients
Comparing the clinical characteristics of patients in the PB group and the non-PB group, it was found that the median age of the PB group was older than that of the non-PB group (P = 0.037), while there were no significant differences in gender, ICU admission rate, cough, fever, wheezing symptoms and medical history between the two groups. The length of hospital stay in the PB group was significantly longer than that in the non-PB group. In terms of laboratory tests: the neutrophil ratio, CRP, PCT, LDH, and IL-6 levels in the PB group were higher than those in the non-PB group (P < 0.05). Chest CT examination showed that there was no significant difference in the number of diseased lung lobes between the two groups. Overall, there was a significant difference in the rate of pulmonary consolidation in the five lobes (χ2 = 20.01, P = 0.0005). Pairwise comparison of the pneumonia positive rate showed that the right lower lobe was significantly higher than other lobes: right lower lobe vs. right middle lobe, P = 0.0331; right lower lobe vs. right upper lobe, P = 0.0004; right lower lobe vs. left upper lobe, P = 0.0003; right lower lobe vs. left lower lobe, P = 0.0018. In terms of bronchoscopy, the PB group was more serious than the non-PB group in terms of mucosal erythema, edema, white secretions, and secretion volume (P < 0.05).
In terms of complications: 70 cases (44.87%) had extrapulmonary complications, 21 cases (13.5%) had pleural effusion, 16 cases (10.3%) had electrolyte abnormalities, 29 cases (18.6%) had cardiovascular complications, 20 cases (12.8%) had abnormal liver function, 29 cases (18.6%) had anemia, 11 cases (7.1%) had abnormal coagulation function, 4 cases (2.6%) had urinary system abnormalities, and 20 cases (12.8%) had sepsis. Extrapulmonary complications such as pleural effusion, sepsis, cardiovascular injury, abnormal liver function, abnormal coagulation function, and renal injury were more common in the PB group than in the non-PB group (all P < 0.05) (Table 1).
Comparison of clinical characteristics between PB patients with and without extrapulmonary complications
The clinical characteristics of PB patients with extrapulmonary complications (EC) and those without complications (non-EC) were compared. There was no significant difference in age and gender distribution between the two groups, but the ICU admission rate in the EC group was significantly higher than that in the non-EC group (P < 0.05). The duration of fever and hospitalization in the EC group was significantly longer than that in the non-EC group (P < 0.05), while there was no significant difference in medical history and wheezing time between the two groups. In terms of laboratory tests, the neutrophil ratio, CRP, PCT, and LDH levels in the EC group were significantly higher than those in the non-EC group (P < 0.05). Chest CT examination showed that there was no significant difference in the number of lesioned lung lobes between the two groups, but the right upper lobe involvement ratio was higher in the EC group. In terms of bronchoscopy, there was no significant difference in mucosal erythema, white secretions, and secretion volume between the two groups, but the incidence of mucosal edema in the non-EC group was significantly higher than that in the EC group (P < 0.05) (Fig. 1; Table 2).
Fig. 1.
Representative clinical findings of a patient with pneumococcal plastic bronchitis (PB): A computed tomography (CT) scan before bronchoscopy showed pulmonary consolidation and atelectasis; B mucosal erythema; C mucosal pallor and edema; D and E bronchoscopy and removal of tubular casts suggestive of PB; F mucosal edema
Table 2.
Comparison of clinical characteristics of PB patients with and without extrapulmonary complications [n (%), IQR]
| Variable | EC(n = 27) | Non-EC (n = 15) | Z/χ2 | P |
|---|---|---|---|---|
| Age, years old | 4 (1.666667, 6.3335) | 3.00 (0.37, 3.62) | 1.603 | 0.109 |
| Gender, Male | 17 (63.0) | 9 (60) | 0.036 | 0.85 |
| ICU, n (%) | 19 (70.4) | 3 (20) | 9.808 | 0.002 |
| Cough,d | 5 (2, 11) | 7.00 (3.00, 25.00) | 1.305 | 0.192 |
| Fever, d | 2 (0.05, 5.5) | 0.00 (0.00, 1.15) | 2.161 | 0.031 |
| Breathing, d | 0 (0, 0) | 0.00 (0.00, 0.00) | 0.613 | 0.540 |
| Medical history, d | 5 (2, 13) | 7.00 (5.00, 25.00) | 1.832 | 0.067 |
| Hospitalization days, d | 15 (13, 25.5) | 12.00 (8.00, 15.50) | 1.958 | 0.050 |
| WBC, 10^9/L | 10.16 (7, 12.095) | 10.26 (7.97, 13.18) | 0.354 | 0.723 |
| Neutral particle ratio | 74.96 (7, 85.75) | 48.00 (33.80, 70.50) | 2.154 | 0.031 |
| Lymphocyte ratio | 19.7 (17, 37.4) | 46.60 (22.70, 55.45) | 2.455 | 0.014 |
| CRP, mg/L | 17.62 (6.2, 79.69) | 5.01 (0.45, 24.19) | 2.022 | 0.043 |
| PCT, ng/ml | 0.76 (07,9.5) | 0.09 (0.05, 0.59) | 2.179 | 0.029 |
| LDH, U/L | 440 (317, 721) | 280.00 (237.50, 294.50) | 2.626 | 0.009 |
| Interleukin-6, ng/ml | 25.48 (7, 64.085) | 8.64 (3.86, 21.20) | 1.720 | 0.085 |
| Number of lobes with pulmonary consolidation | 1(1,2) | 1 (1,2) | 0.499 | 0.618 |
| Right upper lobe, n (%) | 10 (37) | 1 (6.7) | 4.601 | 0.032 |
| Right middle lobe, n (%) | 6 (22.2) | 5 (33.3) | 0.616 | 0.433 |
| Right lower lobe, n (%) | 15 (55.6) | 5 (33.3) | 1.909 | 0.167 |
| Left upper lobe, n (%) | 5 (18.5) | 4 (26.7) | 0.38 | 0.537 |
| Left lower lobe, n (%) | 6 (22.2) | 5 (33.3) | 0.616 | 0.433 |
| Mucosal erythema, n (%) | 7 (25.9) | 4 (26.7) | 0.606 | 0.895 |
| Mucosal edema, n (%) | 25 (92.6) | 11 (40.7) | 6.793 | 0.033 |
| Mucosal pallor, n (%) | 13 (48.1) | 6 (40) | 0.258 | 0.611 |
| Secretion color, n (%) | 24 (88.9) | 14 (93.3) | 0.221 | 0.638 |
| Secretion volume, n (%) | 26 (96.3) | 14 (93.3) | 1.013 | 0.603 |
Correlation analysis between PB, complications and clinical characteristics
Correlation analysis showed that PB was positively correlated with bronchial mucosal erythema (r = 0.32), white secretion (r = 0.39), secretion volume (r = 0.34), extrapulmonary complications (r = 0.24), hospital stay (r = 0.23), neutrophil ratio (r = 0.18), CRP (r = 0.18), PCT (r = 0.25), LDH (r = 0.21), and IL-6 (r = 0.30). Extrapulmonary complications were positively correlated with ICU admission (r = 0.47), right upper lobe involvement (r = 0.16), hospital stay (r = 0.27), neutrophil ratio (r = 0.22), PCT (r = 0.31), LDH (r = 0.30), and IL-6 (r = 0.2), and negatively correlated with cough days (r=−0.35). The length of hospital stay was positively correlated with ICU admission (r = 0.26), right upper lobe involvement (r = 0.21), white secretions (r = 0.23), secretion volume (r = 0.18), extrapulmonary complications (r = 0.27), PB (r = 0.23), CRP (r = 0.34), LDH (r = 0.24), and IL-6 (r = 0.16), and negatively correlated with the number of days with cough (r=−0.16) (Fig. 2).
Fig. 2.
Correlation analysis between PB, EC and clinical characteristics
Logistic regression analysis of patients with and without PB
To investigate the risk factors associated with PB formation in patients with pneumococcal pneumonia, univariate logistic regression analysis was performed (Table 3), and stepwise regression was used to screen for variables with significance < 0.05. Age (P = 0.728), hospitalization days (P = 0.883), CRP (P = 0.838), lactate dehydrogenase (P = 0.232), IL-6 (P = 0.651), amount of secretion (P = 0.595) were excluded by stepwise regression (Fig. 3A). The results showed that mucosal erythema (P = 0.02) and color of discharge (P < 0.01) were risk factors for PB formation. Indicators with P < 0.2 in univariate analysis were used as independent variables for multivariate logistic regression analysis. The results showed that mucosal erythema, abnormal coagulation function, color of secretion and PCT were independent risk factors (Table 4; Fig. 3B). We developed a nomogram model for multiple logistic regression analysis (Fig. 4). The occurrence probability of PB was comprehensively predicted according to PCT, mucosal erythema, abnormal coagulation function, and color of secretion.
Table 3.
Univariate logistic regression analysis of PB
| Variable | Beta | OR | P | 95% CI |
|---|---|---|---|---|
| (constant) | 0.003 | 0.354 | - | |
| Neutral particle ratio | 0.012 | 1.012 | 0.843 | 0.898–1.141 |
| Lymphocyte ratio | 0.002 | 1.002 | 0.972 | 0.878–1.145 |
| PCT | 0.072 | 1.075 | 0.057 | 0.998–1.158 |
| Mucosal erythema | 2.129 | 8.409 | 0.002 | 2.117–33.408 |
| Color of secretion | 2.486 | 12.012 | < 0.001 | 3.174–45.457 |
| Extrapulmonary complications | −0.004 | 0.996 | 0.996 | 0.201–4.932 |
| Pleural effusion | 0.339 | 1.404 | 0.733 | 0.2-9.878 |
| Abnormal coagulation function | 1.828 | 6.221 | 0.143 | 0.539–71.817 |
| Liver damage | 1.041 | 2.831 | 0.249 | 0.482–16.609 |
| Kidney damage | 0.157 | - | 0.999 | - |
Fig. 3.
Binary (A) and multivariate (B) logistic regression in PB, forest map
Table 4.
Drugs use of patients before admission
| Variable | P valve (likelihood ratio) | Exp(B) | 95% Confidence Interval |
|---|---|---|---|
| Mucosal erythema | 0.027 | 2.492 | 1.292 to 5.097 |
| Abnormal coagulation function | 0.091 | 9.516 | 1.400 to 101.6 |
| Color of secretion | 0.003 | 8.027 | 2.739 to 30.52 |
| PCT | 0.050 | 1.084 | 1.016 to 1.179 |
Fig. 4.
Multivariate logistic regression in PB, nomogram
Based on independent risk factors (mucosal erythema, secretion color, abnormal coagulation function, and procalcitonin [PCT]), a multivariate logistic regression prediction model was constructed. The nomogram (Fig. 4) demonstrated that PCT level contributed the most to the total score (0–90 points), followed by coagulation function (0–35 points). ROC curve analysis revealed that the combined prediction achieved an AUC of 0.78 (sensitivity 88.2%, specificity 56.3%), significantly outperforming individual indicators (all P < 0.05). Bootstrap internal validation (1,000 resamples) yielded a corrected C-index of 0.75, and the Hosmer-Lemeshow test indicated good model calibration (P = 0.32). Risk stratification suggested that patients with a total score > 80 had a probability of PB exceeding 50%, warranting prioritized intervention.
ROC curve analysis of the predictive value of each variable for PB
The results of ROC curve analysis showed that mucosal erythema, secretion volume, secretion color, PCT and their combined prediction had certain predictive value for PB (all P < 0.05). The AUCs of mucosal erythema, secretion volume and secretion color were all greater than 0.7. Specifically, the AUC of mucosal erythema was 0.7, with a cut-off value of 0.269, a sensitivity of 0.857 and a specificity of 0.412; the AUC of secretion volume was 0.77, with a cut-off value of 0.405, a sensitivity of 0.738 and a specificity of 0.667; the AUC of secretion color was 0.71, with a cutoff value of 0.431, a sensitivity of 0.905 and a specificity of 0.526; and the AUC of PCT was 0.61, with a cut-off value of 0.412, a sensitivity of 0.796 and a specificity of 0.207. The AUC of the combined prediction was 0.78, the cut-off value was 0.882, the sensitivity was 0.882, and the specificity was 0.563 (Fig. 5).
Fig. 5.
ROC curve of the predictive value of mucosal erythema, secretion volume, secretion color, and PCT for PB
Survival analysis of hospital stay in two groups
Survival analysis was performed to investigate the effects of PB and complications on hospital stay, with a median discharge time of 12 days as survival time and discharge < 12 days as positive. The results showed that the hospital stay of PB patients and patients with extrapulmonary complications was significantly longer than that of non- PB and non-complication patients (Log-rank P = 0.036 and 0.001, respectively). See Fig. 6A and B for details.
Fig. 6.
Survival analysis of the effect of BAL treatment on hospital stay A PB patients and patients with extrapulmonary complications B non- PB and non-complication patients
Prehospital drugs use between the two groups
Eight of the 156 patients were not treated with any drugs (only antibiotics, antiviral and antifungal drugs) before admission. There were no significant differences in the use of Amoxicillin, Cephalosporins, azithromycin, interferon, acyclovir, meropenem, peramivir and Conazoles between the two groups (P > 0.05). There was a significant difference in the use of erythromycin before hospitalization between the two groups (P < 0.05, Table 5).
Table 5.
Drugs use of patients before admission
| Drug | PB | Non-PB | χ2 | P valve |
|---|---|---|---|---|
| Amoxicillin | 9 | 38 | 1.979 | 0.112 |
| Cephalosporins | 20 | 54 | 0.005 | 0.542 |
| Azithromycin | 10 | 29 | 0.033 | 0.518 |
| Erythromycin | 5 | 3 | 5.498 | 0.032 |
| Interferon | 17 | 50 | 0.113 | 0.44 |
| Acyclovir | 5 | 10 | 0.367 | 0.369 |
| Meropenem | 3 | 5 | 0.497 | 0.364 |
| Peramivir | 2 | 5 | 0.012 | 0.602 |
| Conazoles | 0 | 2 | 0.74 | 0.535 |
Socio‑economic characteristics were assessed in the entire cohort (n = 156). Table 6 compares the distribution of each factor between patients with plastic bronchitis (PB) and those with non‑PB obstructive bronchitis. In univariable χ² analysis, incomplete vaccination was significantly more common in PB (61.9% vs. 31.6%, χ² = 11.5, P = 0.001). Passive smoking and under‑nutrition showed non‑significant upward trends, whereas low SES did not differ appreciably.
Table 6.
Socio‑economic & lifestyle comparison between PB and non‑PB groups
| Variable | PB (n = 42) | non‑PB (n = 114) | χ² | P |
|---|---|---|---|---|
| Passive smoke exposure | 16 (38.1%) | 29 (25.4%) | 3.04 | 0.081 |
| Incomplete vaccination | 26 (61.9%) | 36 (31.6%) | 11.53 | 0.001 |
| Under‑nutrition | 11 (26.2%) | 17 (14.9%) | 2.85 | 0.092 |
| Low SES | 20 (47.6%) | 41 (36.0%) | 1.73 | 0.188 |
Multivariable logistic regression (Table 7) identified two independent risk factors for PB: incomplete pneumococcal vaccination (OR = 4.02, 95% CI 1.83–8.83, P = 0.001) and passive cigarette smoke exposure (OR = 2.32, 95% CI 1.00–5.35, P = 0.049). Under‑nutrition and low SES were not retained as significant predictors. The four‑factor model achieved good discrimination (AUC = 0.79) and calibration (Hosmer–Lemeshow P = 0.46).
Table 7.
Multivariable logistic regression of PB bronchitis
| Variable | β (SE) | OR (95% CI) | P |
|---|---|---|---|
| Passive smoke exposure | 0.84 (0.43) | 2.32 (1.00–5.35) | 0.049 |
| Incomplete vaccination | 1.39 (0.40) | 4.02 (1.83–8.83) | 0.001 |
| Under‑nutrition | 0.62 (0.47) | 1.86 (0.75–4.65) | 0.182 |
| Low SES | 0.31 (0.39) | 1.36 (0.63–2.93) | 0.431 |
Discussion
A total of 156 patients with pneumococcal pneumonia diagnosed by bronchoalveolar lavage fluid were included in this study, of which 42 (26.92%) had plastic bronchitis and 114 (73.08%) had non-plastic bronchitis. The clinical characteristics and risk factors of pneumococcal pneumonia combined with PB in children were summarized.
The median age of all patients in this study was 1.92 years. Cough was the most common symptom (92.95%), followed by fever (38.46%) and wheezing (19.87%). 26.92% of cases had concurrent bronchitis. Similar to previous studies on infection-related bronchitis in children, this study found that cough was the most common manifestation, with an incidence of 100%. PB induced by Mycoplasma pneumoniae infection usually occurs in older children and manifests as fever and cough, but the duration of fever and cough in PB patients is shorter [15]. In contrast, in another study, symptoms of PB patients included cough (100%), fever (80%), shortness of breath (28.9%), and wheezing (20.0%), while bocavirus-induced PB often occurs in younger children, accompanied by moderate fever (54.5%) and wheezing (54.5%) [1]. In this study, 70 patients (44.87%) had extrapulmonary complications, of which cardiovascular damage or anemia (18.6%) were the most common, followed by pleural effusion (13.5%) and sepsis (12.8%). Pleural effusion is a common complication of pneumonia and is associated with increased ICU hospitalization and shock rates [15]. Although the current research literature does not directly mention the specific link between pneumococcal pneumonia and abnormal electrolytes, it is crucial to monitor electrolyte levels in critically ill patients (including those with severe pneumonia) [16]. Pneumococcal infection induces systemic inflammation and severe sepsis. The mechanism is that Streptococcus pneumoniae uses dendritic cells (DCs) to promote bacterial dissemination [17], highlighting the importance of pathogen-immune cell crosstalk in the pathophysiology of sepsis and pneumonia. Severe infection can affect the cardiovascular system, leading to complications such as sepsis, pericardial effusion, and myocardial injury [16]. The results suggest that extrapulmonary complications manifested by pulmonary consolidation and atelectasis as well as multiple organ damage are the main clinical features of pneumonia caused by Streptococcus pneumoniae infection. In conclusion, pneumococcal pneumonia has a significant impact on multiple organ systems. Therefore, when dealing with severe cases, it is crucial to closely monitor parameters such as electrolytes, immune function, cardiovascular and other system or organ function.
PB is characterized by the formation of bronchial casts that can obstruct the tracheobronchial tree. It occurs in a variety of clinical diseases, including congenital heart disease, asthma, lung transplantation, and acute respiratory viral infection [1]. Respiratory tract infection is the main cause of type I PB, and common pathogens include Mycoplasma pneumoniae, influenza virus, adenovirus, and bacteria [11, 18, 19]. This study is the first to systematically investigate the clinical features of PB combined with Streptococcus pneumoniae. In previous studies, hematoxylin-eosin staining showed that bronchial casts of PB contained a large amount of inflammatory necrosis and neutrophils [6]. Another study also showed a large number of neutrophil infiltration and necrosis and exfoliation of epithelial cells in the pathological examination of the cast [11]. The present study showed that the serum neutrophil ratio was significantly increased in patients with PB, which is consistent with recent research results. Studies have shown that neutrophil accumulation is generally considered to play a key role in host defense during bacterial infection, but it also significantly causes lung damage and immune destruction, thereby promoting the invasion of pneumococci into the bloodstream [20]. PCT is an important inflammatory factor reflecting bacterial infection. The results of this study showed that it is one of the independent risk factors for pneumococcal PB. This is consistent with the findings of other researchers, that is, PCT positivity (> 0.5 ng/mL) can be used as a surrogate marker for severe pneumonia [21]. In another study on PB caused by adenovirus pneumonia, PCT was also identified as one of the independent risk factors for mucus plug formation [7].
Bronchial cast obstruction can lead to pulmonary consolidation and atelectasis. In this study, the right lower lung was the main site of lesions. This is related to the anatomical characteristics of the right main bronchus, such as being straighter and thicker, and the difficulty in clearing sputum in the lower lung lobe. Patients in the PB group showed more severe symptoms in terms of mucosal erythema, edema, increased white secretions, and increased secretion volume. This is consistent with the results of Nursoy et al., who believed that the amount of secretions could affect lung function. As the bronchoscopic secretion score increased, the expiratory volume and the first second value of forced vital capacity gradually decreased, and the bronchial Bhalla score and bronchial mucosal inflammation worsened [22]. The results of this study showed that the amount of secretions, mucosal erythema, and secretion color were independent risk factors for PB. Increased mucosal erythema and edema indicate active inflammation and vascular changes in the bronchial tree. The above changes can lead to airway stenosis, ventilation disorders, and increased airway resistance. Therefore, clinicians should closely monitor airway obstruction and respiratory distress in patients with severe mucosal erythema. White secretions indicate excessive mucus secretion from the bronchial epithelium. Large amounts of mucus can block the airway, hinder gas exchange, and increase the risk of infection. The results of bronchoscopy in the PB group showed severe mucosal erythema, edema, increased white secretions, and increased secretion volume, reflecting the intensity of inflammatory response and mucus production. The results showed that the occurrence of PB is closely related to severe airway inflammation and large amounts of secretions. Therefore, early identification of risk factors and appropriate intervention measures, such as early use of anti-inflammatory drugs and timely bronchoscopy, can help improve the prognosis of PB patients [8]. In the study by Wu et al., bronchitis score was identified as an independent risk factor for severe Mycoplasma pneumoniae pneumonia and can reflect the severity of pneumonia. They believe that by evaluating the amount of secretions, mucosal erythema, edema, and secretion color, the degree of bronchial wall damage and bronchial sputum obstruction can be directly evaluated [23]. This study also showed that the hospital stay of the non-PB group was significantly shorter than that of the PB group, indicating that PB is an important factor affecting the effect of hospitalization treatment. Removal of sputum plugs under fiberoptic bronchoscope is the most important means to improve ventilation [18, 19].
Typically, pneumonia affects multiple lobes [24], but this study found that the probability of right lower lung consolidation in patients with pneumococcal pneumonia (SPP) was higher than that in other lobes. The surface protein A of Streptococcus pneumoniae causes Streptococcus pneumoniae to attach to dying lung epithelial cells, causing massive cell necrosis and inducing inflammatory response, which is one of the mechanisms of pulmonary consolidation [25]. Therefore, clinicians should consider the distribution characteristics of pulmonary consolidation when evaluating suspected SPP patients, which affects treatment decisions, including the use of bronchoscopy, the choice of antibiotics, and the duration of treatment. Previous studies have shown that children with atelectasis or pulmonary consolidation caused by Mycoplasma pneumoniae often have a large amount of bronchial secretions, which may only appear as pale or erythematous endothelium. Therefore, bronchoscopy combined with CT examination can more comprehensively evaluate lung inflammatory changes than bronchoscopy alone [26]. However, in this study, CT showed no significant difference in the number of pulmonary consolidation between the PB group and the non-PB group. More detailed and reliable CT evaluation methods are needed for further research. The results of this research team also support the early bronchoscopy and bronchoalveolar lavage treatment of children with lung infection who have radiographic manifestations of large-area pulmonary consolidation or atelectasis. This not only provides the possibility of discovering plastic bronchitis, but also allows patients to benefit as early as possible [23, 27].
By incorporating socio‑economic variables, we demonstrated that incomplete pneumococcal vaccination and household smoke exposure substantially increase the likelihood of developing PB bronchitis. These findings underscore the importance of comprehensive vaccination programmes and smoke‑free home environments. Although low SES and under‑nutrition were not independent predictors after adjustment, their univariable trends suggest that larger studies are required. Future work should also integrate microbiome analyses to elucidate environment–host interactions in PB.
This study has limitations: first, this is a retrospective study with a relatively small sample size; second, there is a lack of pathological analysis results for the characteristics of SPP combined with PB; third, the relationship between SPP resistance and PB development was not analyzed. Fourth, we could not perform this analysis because many data on prediagnostic medication use were missing. The above issues require further research to gain a deeper understanding of the etiology of PB and optimize treatment strategies.
Conclusion
This study found that the main clinical features of pneumococcal pneumonia combined with plastic bronchitis were high incidence in young children, cough as the main symptom, right lower lung consolidation and atelectasis. The amount of secretions, mucosal erythema, secretion color (yellow-white) and PCT level were independent risk factors for plastic bronchitis and had a high value in predicting the occurrence of plastic bronchitis. Based on the above findings, it is recommended that patients with risk factors undergo bronchoscopy as early as possible to diagnose and intervene in plastic bronchitis in a timely manner.
Acknowledgements
Not applicable.
Abbreviations
- CRP
C-reactive protein
- PCT
Procalcitonin
- SPP
Streptococcus pneumoniae
- LDH
Lactate dehydrogenase
- IL-6
Interleukin-6
- PB
Plastic bronchitis
- EC
Extrapulmonary complications
- CT
Computed tomography
- FOB
Fiberoptic bronchoscopy
- BAL
Bronchoalveolar lavage
- AUC
Area under the curve
- ROC
Receiver operating characteristic curve
Authors’ contributions
Study design: Guo XX, Xu YL, Ren YS, Fan SS, Kong LF, Xu YP, Li DD, Li SJ. Data acquisition: Guo XX, Xu YL, Ren YS, Fan SS, Kong LF, Xu YP, Li DD, Li SJ. Data analysis and interpretation: Xu YL, Ren YS, Fan SS, Kong LF, Xu YP. Manuscript preparation: Guo XX, Xu YL, Ren YS, Fan SS, Kong LF, Xu YP. Critical revision of the manuscript for intellectual content: Li SJ, Li DD. Manuscript review: Guo XX, Xu YL, Ren YS, Fan SS, Kong LF, Xu YP, Li DD, Li SJ. Obtaining financing: None.
Funding
Not applicable.
Data availability
Data will be made available on request.
Declarations
Ethics approval and consent to participate
This study was conducted in accordance with the Declaration of Helsinki and approved by the Research Ethics Committee of The First Affiliated Hospital of Xinxiang Medical University (Ethics Number: EC-023-448). Due to the nature of retrospective study and anonymized patien’s information, informed consent is waived with the approval of Ethics Committee of The First Affiliated Hospital of Xinxiang Medical University. All methods were carried out in accordance with relevant guidelines and regulations.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s Note
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Contributor Information
Duo-Duo Li, Email: LDduo_99@126.com.
Shu-Jun Li, Email: ruolin2223@126.com.
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Data Availability Statement
Data will be made available on request.