Clinical characteristics
There were 255 children with MPP who were treated with bronchoscopy. The mucus plug group accounted for 90 (35.3%) cases and the control group for 165 (64.7%) cases. The mean ages of the mucus plug and control group patients were 6.10±2.85 years and 4.50±2.93 years, respectively, with a significant difference (P < 0.05). The males in the mucus plug group and the control group were 49 (54.4%) of 90 and 89 (53.9%) of 165, respectively, and the difference was not statistically significant (P > 0.05; Table 1). In the mucus plug group, children <2 years of age were significantly less than 2–6 years old and >6 years old, with children >6 years old being the majority, and the difference was statistically significant (P < 0.017; Fig. 1). The univariate analysis showed that the children in the mucus plug group were older, had a longer fever duration, longer hospital stay, higher fever peak, more cases of fever, wheezing symptoms and allergies, azithromycin (intravenous or oral) or corticosteroids (intravenous or oral) were administered later, and the neutrophil, C-reactive protein (CRP), lactate dehydrogenase (LDH), D-dimer (DD), sputum MP-DNA copy number, total IgA, and the CD19+CD23+ levels were higher, while the PA levels were lower. In addition, lung consolidation and pleural effusion cases were greater (Table 1). The chest radiograph or computed tomography (CT) showed that the lung inflammation in the mucous group was primarily in the bottom right lung (23 [25.6%] of 90) and the bottom left lung (19 [21.1%]; Fig. 2). Fig. 3 is a bronchoscopic performance and imaging features of a 10-year-old MPP patient.
Table 1 Clinical characteristics of patients in the mucus plug and control group
Variables
|
Mucus plug group (n = 90)
|
Control group (n = 165)
|
P value
|
Characteristics
|
|
|
|
Gender (male/female, n)
|
49/41
|
89/76
|
0.938
|
Age (`x ± s)/year
|
6.10±2.85
|
4.50±2.93
|
<0.01
|
Length of hospitalization (`x ± s) /d
|
10.72±3.47
|
8.81±2.72
|
<0.01
|
Course before admission [M(P25–P75)]/d
|
8 (6, 10)
|
7 (5, 11)
|
0.869
|
Allergic constitution [n (%)]
|
40 (44.4)
|
33 (21.2)
|
<0.01
|
Signs and symptoms
|
|
|
|
Fever [n (%)]
|
86 (95.6)
|
135 (81.8)
|
0.002
|
Heat range (`x ± s) /d
|
9.72±3.80
|
5.00±3.98
|
<0.01
|
Hot peak [M(P25–P75), °C]
|
39.6 (39, 40)
|
39 (38.5, 39.7)
|
<0.01
|
Shortness of breath [n (%)]
|
6 (6.7)
|
8 (4.8)
|
0.542
|
Breather [n (%)]
|
7 (7.8)
|
41 (24.8)
|
0.01
|
Lung rales [n (%)]
|
40 (44.4)
|
68 (41.2)
|
0.618
|
Lung wheezing [n (%)]
|
6 (6.6)
|
27 (16.3)
|
0.27
|
Reduced breath sounds [n (%)]
|
14 (15.6)
|
21 (1.3)
|
0.531
|
Laboratory characteristics
|
|
|
|
WBC [M(P25–P75)]/ ×109 L−1
|
7.63 (5.97, 11.35)
|
7.97 (6.12, 10.64)
|
0.844
|
Neutrophil (`x ± s)/%
|
67.34±12.78
|
57.53±15.20
|
<0.01
|
Eos [M(P25–P75)]/×109 L−1
|
0.4 (0.045, 1.325)
|
0.3 (0.07, 1.5)
|
0.866
|
CRP [M(P25–P75)]/mg·L−1
|
25.72 (12.62, 51.23)
|
7.58 (2.58, 18.23)
|
<0.01
|
PLT [M(P25–P75)]/×109 L−1
|
275.5 (231.75, 356)
|
321 (232, 394)
|
0.109
|
LDH [M(P25–P75)]/U·L−1
|
545.9 (397.3, 655.5)
|
389.3 (340.0, 389.3)
|
<0.01
|
PA [M(P25–P75)]/mg·L−1
|
114 (92.75, 134)
|
142 (115, 195.5)
|
<0.01
|
DD [M(P25–P75)]/μg·L−1
|
1207 (484.5, 3677.75)
|
367 (187, 367)
|
<0.01
|
CK-MB [M(P25–P75)]/ng·mL−1
|
0.9 (0.5, 1.5)
|
1.1 (0.6, 1.75)
|
0.295
|
ALT [M(P25–P75)]/U·L−1
|
17.6 (12.55, 30.725)
|
12.9 (10.1, 17.8)
|
<0.01
|
AST [M(P25–P75)]/U·L−1
|
34.6 (27.425, 43.725)
|
30.2 (24.95, 37.95)
|
0.003
|
Serum MP-IgM
|
3.46 (1.36, 5.49)
|
3.2 (1.15, 5.14)
|
0.154
|
Sputum MP-DNA copy number [n (%)]
|
|
|
|
Low load group
|
3 (3.3)
|
20 (12.1)
|
0.019
|
Medium load group
|
13 (14.4)
|
42 (25.5)
|
0.041
|
High load group
|
74 (82.2)
|
103 (62.4)
|
0.001
|
Humoral immunity
|
|
|
|
IgG (`x ± s)/g·L−1
|
9.79±2.86
|
9.43±3.08
|
0.357
|
IgA [M(P25–P75)]/g·L−1
|
1.27 (0.96, 1.76)
|
1.04 (0.6, 1.53)
|
0.007
|
IgM [M(P25–P75)]/g·L−1
|
1.49 (1.09, 2.20)
|
1.37 (0.95, 1.92)
|
0.061
|
Cellular immunity [M(P25–P75), %]
|
|
|
|
CD3+
|
66.96 (61.2, 73.05)
|
65.5 (60.05, 72.15)
|
0.634
|
CD3+CD4+
|
34.14 (28.3, 40.32)
|
34.2 (30.25, 39.2)
|
0.524
|
CD3+CD8+
|
27.25 (21.5, 27.25)
|
25.8 (21.5, 30.2)
|
0.24
|
CD4+/CD8+
|
1.30 (1.0, 1.3)
|
1.3 (1.1, 1.7)
|
0.117
|
CD3-CD (15+56) +
|
10.35 (5.7, 15.7)
|
10.2 (7.1, 14.8)
|
0.715
|
CD3-CD19+
|
19.2 (14.02, 25.92)
|
18.7 (12.95, 26.85)
|
0.983
|
CD19+CD23+
|
7.9 (5.4, 12.72)
|
9.4 (6.55, 13.6)
|
0.023
|
Radiological characteristics [n (%)]
|
|
|
|
Lung consolidation
|
84 (93.3)
|
126 (76.36)
|
0.001
|
Atelectasis
|
9 (10)
|
8 (4.8)
|
0.123
|
Pleural effusion
|
19 (21.1)
|
18 (10.9)
|
0.040
|
Pleural effusion site [n (%)]
|
|
|
|
Left side
|
9 (10)
|
10 (6.1)
|
0.331
|
Right side
|
10 (11.1)
|
11 (6.7)
|
0.238
|
Treatment
|
|
|
|
Medication time [M(P25–P75)]/Day n of course
|
|
|
|
Azithromycin
|
5.5 (4, 7)
|
4 (3, 6)
|
0.012
|
corticosteroids
|
7 (5, 9)
|
5 (3, 8)
|
0.003
|
Fog time before tracheoscopy[M(P25–P75)]/d
|
3 (2, 4)
|
3 (2, 5)
|
0.525
|
Sputum MP-DNA copy number: low load group, <1 × 104 L−1; medium load group, 1 × 104 L−1 –106 L−1; high load group, >1 × 106 L−1
ALT = alanine aminotransferase; AST = aspartate aminotransferase; CD = cluster of differentiation; CK-MB = creatine kinase-MB; CRP = C reactive protein; DD = D-dimer; IgA = immunoglobulin A; IgG = immunoglobulin G; LDH = lactate dehydrogenase; MP = Mycoplasma pneumonia; PA = Prealbumin; PLT = Platelets; WBC = white blood cells
Analysis of risk factors for BMP formation in children with MPP
A univariate logistic regression showed that the PA level (odds ratio [OR], 1.015; 95% confidence interval [CI], 1.001–1.030), timing of corticosteroids use (use in the first few days; OR, 0.802; 95% CI, 0.663–0.970), CRP level (OR, 0.986; 95% CI, 0.944–0.992), and LDH level (OR, 0.996; 95% CI, 0.992–0.999) were independent risk factors for MPP mucus plug formation (P < 0.05, Table 2). The ROC curve analysis showed that when the optimal thresholds for PA, use of corticosteroids during the course, CRP, and LDH were ≤144.5 mg/L, ≥4.5 days, ≥12.27 mg/L, and ≥462.65 U/L, respectively, their sensitivity and specificity to predict BMP formation were 87.8% and 48.5%, 78.9% and 40%, 76.7% and 63.6%, and 65.6% and 72.1%, respectively (Fig. 4).
Table 2 Logistic regression analysis of risk factors related to BMP formation in MPP
Variable
|
Partial regression coefficient (β)
|
SE
|
Wald χ2 value
|
P value
|
OR (95% CI)
|
CRP (mg/L)
|
−0.033
|
0.013
|
6.604
|
0.01
|
0.986 (0.944–0.992)
|
LDH (U/L)
|
−0.004
|
0.002
|
5.419
|
0.02
|
0.996 (0.992–0.999)
|
PA (mg/L)
|
0.015
|
0.007
|
4.655
|
0.031
|
1.015 (1.001–1.030)
|
Corticosteroids (d)
|
−0.220
|
0.097
|
5.151
|
0.023
|
0.802 (0.663–0.970)
|
Constant
|
14.063
|
6.451
|
4.753
|
0.029
|
——
|
Corticosteroids, use corticosteroids for the first few days
BMP = bronchial mucus plug; CI = confidence interval; CRP = C reactive protein; LDH = lactate dehydrogenase; MPP = M. pneumoniae pneumonia; OR = odds ratio; PA = prealbumin; SE = standard error
Logistic regression analysis after assigning risk factors for BMP formation
The critical values of the independent factors were assigned to evaluate the risk of BMP formation. The logistic regression analysis showed a statistical significance (P < 0.05, Table 3). Based on the logistic regression analysis, a lower PA lever (>144.5 vs ≤144.5 mg/L; OR, 6.514; 95% CI, 3.410–12.443), later corticosteroid therapy (≥4.5 vs <4.5 d; OR, 2.333; 95% CI, 1.298–4.195), a higher CRP level (<12.27 vs ≥12.27 mg/L; OR, 5.409; 95% CI, 3.041–9.622), and a higher LDH level (<462.65 vs ≥462.65 U/L; OR, 4.377; 95% CI, 2.533–7.565) were each independently associated with BMP formation (Table 3).
Table 3 Logistic regression analysis after assigning risk factors for BMP formation
Variable (assignment)
|
Wald χ2
|
P
|
OR (95% CI)
|
CRP (<12.27 mg/L = 0 ≥12.27 mg/L = 1)
|
33.000
|
0.000
|
5.409 (3.041−9.622)
|
LDH (<462.65 U/L = 0 ≥462.65 U/L = 1)
|
27.983
|
0.000
|
4.377 (2.533−7.565)
|
PA (>144.5 mg/L = 0 ≤144.5 mg/L = 1)
|
32.210
|
0.000
|
6.514 (3.410−12.443)
|
corticosteroids (<4.5 d = 0 ≥4.5 d = 1)
|
8.018
|
0.005
|
2.333 (1.298−4.195)
|
Corticosteroids, use corticosteroids for the first few days
BMP = bronchial mucus plug; CI = confidence interval; CRP = C reactive protein; LDH = lactate dehydrogenase; OR = odds ratio; PA = prealbumin
Percentage of mucous plug patients in the MPP scoring groups
The independent risk factors were scored according to their OR value. The time of corticosteroids application ≥4.5 days was one point; a CRP ≥12.27 mg/L and an LDH ≥462.65 U/L was two points; and a PA ≤144.5 mg/L was three points. According to the scores, the MPP patients were divided into a high-risk group (7–8 points), a middle-risk group (4–6 points), and a low-risk group (0–3 points). Among them, 53 cases were in the high-risk group and 44 cases (83.02%) were caused by mucus plugs. There were 102 cases in the middle-risk group, 35 cases (34.3%) with mucus plugs, 100 cases in the low-risk group, and 11 cases (11%) with mucus plugs (Fig. 5).