General clinical data
A total of 1001 patients were enrolled in the test cohort from September 2019 to February 2021, while another 230 patients were enrolled in the validation cohort from March 2021 to August 2021. The baseline characteristics of patients who underwent PTNB are shown in Table 1. Among the derivation cohort, 611 were men (61%), and the mean age of all patients was 63.81±12, ranging from 14 to 90. In the validation cohort, 81 patients were men (70%), and the mean age of all patients was 66.56±10.86, ranging from 41 to 87.
According to the pathology reports, 660 were malignancies, 85 were confirmed as tuberculosis (n=83) and mycosis (n=2), 224 were nonspecific inflammations and 32 were judged to be nondiagnostic in the derivation cohort. One hundred forty were malignancies, 18 were confirmed as tuberculosis (n=10) and mycosis (n=8), 60 were nonspecific inflammations and 16 were judged to be nondiagnostic in the validation cohort.
Of all the 169 pneumothorax cases among the patients, (16.9%) occurred after PTNB, while 12 cases (7%) were defined as severe pneumothorax that needed closed thoracic drainage in the derivation cohort. The corresponding rate in the validation cohort was 36 pneumothorax cases (15.7%), and 9 case (3.9%) needed intervention. The overall rate of hemoptysis was 3.4% (n=34), with most cases having volumes of hemoptysis < 20 mL. One patient died because of massive hemoptysis in the derivation cohort. The corresponding hemoptysis rate in the validation cohort was 3%(n=7) and no one died.
Clustering for pneumothorax
After calculating the silhouette width for clusters ranging from 2 to 10 for the PAM algorithm, we noticed that 2 clusters yielded the highest value (figure 2A). After running the algorithm and selecting two clusters (figure 2B), we interpreted the clusters by running a summary on each cluster (figure 2 B). Based on these results, it seemed that Cluster 1 was mainly younger/more number of lesion puncture/higher puncture depth with a heavy smoking index. Cluster 2, on the contrary, was mainly older/fewer number of lesion puncture/lower puncture depth with a light smoking index.
Derivation of a risk prediction model for pneumothorax and development of a risk scoring system.
The final risk prediction model with an AUROC of 0.673 (figure 3A) contained seven variables, including age, number of lesion puncture, puncture depth, smoking index, number of specimens, needle path bleeding, and lobular lesion (table 1), that were all statistically significantly associated with pneumothorax (p < 0.05) in the regression analyses in the derivation cohort, which could be visualized by a forest tree plot (figure 2C). We used these seven variables to develop a risk scale to predict pneumothorax. The categories and assignment of points in each variable are summarized in Tables 2 and 3. The scale ranged from -13 to 26 points. Risks associated with point totals are demonstrated in Table 4.
Table 1 Demographics of patients with or without pneumothorax undergone CT-guided PTNB in derivation and validation cohort. Data are presented as the mean ± SD or as a number with/without the percentage in parenthesis, as appropriate. Number of lesion puncture, Puncture number. Number of specimens, Specimen. Needle path bleeding, tissue bleeding. Lobularity of the lesion, lobularity. NA, not available.
Demographics
|
Derivation
|
Validation
|
|
Pneumothorax Yes (N=169)
|
Pneumothorax No (N=832)
|
P
|
OR
|
95%CI
|
Pneumothorax Yes (N=36)
|
Pneumothorax No (N=194)
|
P
|
OR
|
95%CI
|
Male gender
|
115(68%)
|
496(60%)
|
0.05
|
|
|
18(50%)
|
144(82%)
|
|
|
|
Diagnosis
|
|
malignancy
|
103(61%)
|
557(67%)
|
NA
|
NA
|
NA
|
22(61%)
|
118(75%)
|
NA
|
NA
|
NA
|
tuberculosis
|
15(9%)
|
68(8%)
|
NA
|
NA
|
NA
|
0
|
10(6%)
|
NA
|
NA
|
NA
|
mycosis
|
0
|
2(0.2%)
|
NA
|
NA
|
NA
|
0
|
8(5%)
|
NA
|
NA
|
NA
|
nonspecific inflammation
|
41(24%)
|
183(22%)
|
NA
|
NA
|
NA
|
12(33%)
|
42(27%)
|
NA
|
NA
|
NA
|
nondiagnostic
|
10(6%)
|
22(3%)
|
NA
|
NA
|
NA
|
2(6%)
|
14(8%)
|
NA
|
NA
|
NA
|
Variables included in logistic regression
|
|
|
|
Age
|
65.1 ±12
|
63.5 ±11
|
0.05
|
1.022
|
1.006-1.038
|
66.56 ±10.86
|
64.39 ±10.6
|
0.1
|
NA
|
NA
|
Smoking index
|
19.4±24
|
14.6±22
|
0.01
|
1.01
|
1.003-1.017
|
9.44±16.97
|
15.34±30.16
|
0.02
|
NA
|
NA
|
Lobular of the lesion
|
58(34%)
|
378(45%)
|
0.01
|
0.592
|
0.413-0.849
|
3(17%)
|
31(32%)
|
0.01
|
NA
|
NA
|
Puncture number
|
3.7±1.6
|
2.6±1.4
|
0.05
|
1.246
|
1.07- 1.45
|
3.78±1.11
|
4.07±1.66
|
0.06
|
NA
|
NA
|
Puncture depth
|
7.5±1.4
|
5.4±1.8
|
0.01
|
1.122
|
1.018-1.236
|
5±1.85
|
5.14±1.69
|
0.08
|
NA
|
NA
|
Specimen
|
3.1±1.1
|
3.9±1.0
|
0.05
|
0.743
|
0.595- 0.927
|
3.33±1.84
|
3.43±1.35
|
0.76
|
NA
|
NA
|
Tissue bleeding
|
2(1%)
|
92(11%)
|
0.00011
|
0.089
|
0.025-0.32
|
0
|
13(13.4%)
|
0.21
|
NA
|
NA
|
Table 2 Scores associated with each of the categories of the risk factors. βi, regression units; B, constant. Number of lesion puncture, Puncture number. Number of specimens, Specimen. Needle path bleeding, tissue bleeding. lobularity of the lesion, lobularity
Risk factor
|
Categories
|
Reference value (Wij)
|
βi
|
βi(Wij-WiREF)
|
βi(Wij-WiREF)/B
(Scores)
|
Age(year)
|
10-19
|
14.5= WiREF
|
0.029812
|
0
|
0
|
|
20-29
|
24.5
|
|
0.29812
|
1
|
|
30-39
|
34.5
|
|
0.59624
|
2
|
|
40-49
|
44.5
|
|
0.89436
|
3
|
|
50-59
|
54.5
|
|
1.19248
|
4
|
|
60-69
|
64.5
|
|
1.4906
|
5
|
|
70-79
|
74.5
|
|
1.78872
|
6
|
|
80-89
|
84.5
|
|
2.08684
|
7
|
Puncture number
|
1-4
|
2.5= WiREF
|
0.178844
|
0
|
0
|
|
5-8
|
6.5
|
|
0.715376
|
2
|
|
9-12
|
10.5
|
|
1.430752
|
5
|
Puncture depth(cm)
|
1-4
|
2.5= WiREF
|
0.131870
|
0
|
0
|
|
5-8
|
6.5
|
|
0.52748
|
2
|
|
9-12
|
10.5
|
|
1.05496
|
4
|
Smoking index(packyear)
|
10-49
|
25= WiREF
|
0.008493
|
0
|
0
|
|
50-89
|
65
|
|
0.33972
|
1
|
|
90-129
|
105
|
|
0.67944
|
2
|
|
>130
|
145
|
|
1.01916
|
3
|
Specimen
|
1-4
|
2.5
|
-0.253484
|
0
|
0
|
|
5-8
|
6.5
|
|
-1.01
|
-3
|
Tissue bleeding
|
N
|
0
|
-2.295845
|
0.00
|
0
|
|
Y
|
1
|
|
-2.30
|
-8
|
lobularity
|
N
|
0
|
-0.596527
|
0.00
|
0
|
|
Y
|
1
|
|
-0.60
|
-2
|
Table 3 Risk scoring system for predicting pneumothorax in PTNB.
Risk factor
|
Category
|
Score
|
Age (year)
|
10-19
|
0
|
|
20-29
|
1
|
|
30-39
|
2
|
|
40-49
|
3
|
|
50-59
|
4
|
|
60-69
|
5
|
|
70-79
|
6
|
|
80-89
|
7
|
Puncture number
|
1-4
|
0
|
|
5-8
|
2
|
|
9-12
|
5
|
Puncture depth (cm)
|
1-4
|
0
|
|
5-8
|
2
|
|
9-12
|
4
|
Smoking index (packyear)
|
10-49
|
0
|
|
50-89
|
1
|
|
90-129
|
2
|
|
>130
|
3
|
Specimen
|
1-4
|
0
|
|
5-8
|
-3
|
Tissue bleeding
|
N
|
0
|
|
Y
|
-8
|
lobularity
|
N
|
0
|
|
Y
|
-2
|
Table 4 Scores associated with estimate of risk.
Point total
|
Estimate of risk
|
Estimate of risk (%)
|
-13
|
0.00644457
|
0.644457
|
…
|
|
|
1
|
0.04967926
|
4.967926
|
2
|
0.057208
|
5.7208
|
3
|
0.06579869
|
6.579869
|
4
|
0.075576
|
7.5576
|
5
|
0.08667138
|
8.667138
|
6
|
0.09922084
|
9.922084
|
7
|
0.1133619
|
11.33619
|
8
|
0.1292291
|
12.92291
|
9
|
0.1469492
|
14.69492
|
10
|
0.1666342
|
16.66342
|
11
|
0.1883737
|
18.83737
|
12
|
0.2122273
|
21.22273
|
13
|
0.2382148
|
23.82148
|
14
|
0.2663087
|
26.63087
|
15
|
0.2964267
|
29.64267
|
16
|
0.3284261
|
32.84261
|
17
|
0.3621021
|
36.21021
|
18
|
0.3971889
|
39.71889
|
19
|
0.4333657
|
43.33657
|
Validation of the risk scoring system
Internal validation
In the derivation cohorts, the risk scoring system could only achieve an AUROC of 0.601 in the evaluation of predicting pneumothorax (figure 3B). However, the subgroup analysis demonstrated that with increasing age, the predictive effect of the risk scoring system was high. In the group with patients older than 80 years, the AUROC was as high as 0.766 (figure 3C/D). To obtain a high predictive effect, we excluded protective predictors, such as the number of specimens, needle path bleeding, and lobularity of the lesion, one by one to test whether the prediction effect could be higher, but combining all predictors had the highest AUROC (figure 3E). The predictions made from the risk model were in alignment with the observed outcomes suggested by Hosmer-Lemeshow tests (P=0.33). The cutoff score suggested by Youden’s index was 15 points in the derivation cohorts.
External validation
In the validation cohort, the risk scoring system obtained an AUROC of 0.736 in the evaluation of predicting pneumothorax (figure 3F). The cutoff score suggested by Youden’s index was 11 points in the validation cohort.