A total of 286 patients were included in this study; 143 were case subjects and 143 were control subjects.286 patients were randomly divided into a training set and an internal validation set at a ratio of 3:1.Training set containing 102 case subjects and 112 control subjects were used to development model and nomogram and validation set containing 40 case subjects and 32 control subjects were used to internal validate.Table1 listed the demographic and clinical characteristics of pulmonary tuberculosis patients in the training set and validation set.As you can see in table1,the ration of case subjects to all subjects was comparable between two data sets (47.7% vs 56.9%; P =0.173).
Table1 Clinical characteristics of PTB patients in the training set and validation set
Variable
|
Training set(n=214)
|
Validation set(n=72)
|
p
|
Pulmonary fungal infection[n(%)]
Yes
No
|
102(47.7)
112(52.3)
|
41(56.9)
31(43.1)
|
0.173
|
Age[n(%)]
>65years old
≤65years old
|
54(25.2)
160(74.8)
|
16(22.2)
56(77.8)
|
0.607
|
Gender[n(%)]
Male
Female
|
164(76.6)
50(23.4)
|
48(66.7)
24(33.3)
|
0.095
|
Address[n(%)]
North
South
|
206(96.3)
8(3.7)
|
71(98.6)
1(1.4)
|
0.458
|
Smoke[n(%)]
Yes
No
|
89(41.6)
125(58.4)
|
29(40.3)
43(59.7)
|
0.845
|
Drink[n(%)]
Yes
No
|
67(31.3)
147(68.7)
|
22(30.6)
50(69.4)
|
0.905
|
Category[n(%)]
Initial
Recurrent
|
155(72.4)
59(27.6)
|
16(22.2)
56(77.8)
|
0.372
|
Drug resistance[n(%)]
No drug resistance
Single-drug resistance
Multi-drug resistance
|
178(83.2)
17(7.9)
19(8.9)
|
59(81.9)
4(5.6)
9(12.5)
|
0.563
|
Illness course[n(%)]
≤1year
>1year,≤5years
>5years,≤10years
>10years
|
104(48.6)
59(27.6)
19(8.9)
32(15.0)
|
33(45.8)
13(18.1)
14(19.4)
12(16.7)
|
0.062
|
Pulmonary cavitation[n(%)]
Yes
No
|
126(58.9)
88(41.1)
|
34(7.2)
38(52.8)
|
0.085
|
Pleural effussion[n(%)]
Yes
No
|
82(38.3)
132(61.7)
|
25(34.7)
47(65.3)
|
0.585
|
Regular anti-tuberculosis[n(%)]
Yes
No
|
121(56.5)
93(43.5)
|
42(58.3)
30(41.7)
|
0.791
|
Advanced antibiotics were used for at lest 1 week[n(%)]
Yes
No
|
89(41.6)
125(58.4)
|
35(48.6)
37(51.4)
|
0.298
|
Glucocorticoid were used for at lest 2 weeks[n(%)]
Yes
No
|
31(14.5)
183(85.5)
|
8(11.1)
64(88.9)
|
0.470
|
Chemotherapy or immunosuppressants[n(%)]
Yes
No
|
10(4.7)
204(95.3)
|
1(1.4)
71(98.6)
|
0.210
|
Invasive operation[n(%)]
Yes
No
|
150(70.1)
64(29.9)
|
48(66.7)
24(33.3)
|
0.586
|
Surgery[n(%)]
Yes
No
|
81(37.9)
133(62.1)
|
27(37.5)
45(62.5)
|
0.958
|
Bacterial infection in the lungs [n(%)]
Yes
No
|
27(12.6)
187(87.4)
|
12(16.7)
60(83.3)
|
0.386
|
Chronic bronchitis/ COPD/Bronchitis/Asthma[n(%)]
Yes
No
|
28(13.1)
186(86.9)
|
8(11.1)
64(88.9)
|
0.662
|
Silicosis[n(%)]
Yes
No
|
3(1.4)
211(98.6)
|
4(5.6)
68(94.4)
|
0.070
|
Interstitial lung disease[n(%)]
Yes
No
|
7(3.3)
207(96.7)
|
2(2.8)
70(97.2)
|
1.000
|
Hypohepatia[n(%)]
Yes
No
|
68(31.8)
146(68.2)
|
18(25.0)
54(75.0)
|
0.278
|
Renal inadequacy[n(%)]
Yes
No
|
15(7.0)
199(93.0)
|
1(1.4)
71(98.6)
|
0.081
|
Tumor / Hematological disease[n(%)]
Yes
No
|
12(5.6)
202(94.4)
|
5(6.9)
67(93.1)
|
0.773
|
Hypoproteinemia[n(%)]
Yes
No
|
77(36.0)
137(64.0)
|
28(38.9)
44(61.1)
|
0.658
|
Anemia[n(%)]
Yes
No
|
62(29.0)
152(71.0)
|
21(29.2)
51(70.8)
|
0.975
|
Diabetes[n(%)]
Yes
No
|
49(22.9)
165(77.1)
|
19(26.4)
53(73.6)
|
0.547
|
3.1 Predictors Entering the Model
The characteristics of PTB patients with and without pulmonary fungal infection in training set were summarized in Table 2. The factors of age,category, illness course,pulmonary cavitation,pleural effussion,advanced antibiotics were used for at lest 1 week,chemotherapy or immunosuppressants,surgery,bacterial infection in the lungs, chronicbronchitis or chronic obstructive pulmonary disease or bronchitis or asthma,hypoproteinemia,anemia were significantly associated with pulmonary fungal infection,as evaluated by univariate analyses.Table 3 shows the results from the multivariate logistic analyses,and the following seven factors were statistically significant : illness course,pulmonary cavitation,advanced antibiotics were used for at lest 1 week,chemotherapy or immunosuppressants,surgery,bacterial infection in the lungs,hypoproteinemia.(Table 2,3)
Table 2 Univariate analysis of PTB complicated by pulmonary fungal infection (training dataset, N=214)
Variable
|
Case group
(n=102)
|
Control group
(n=112)
|
X2 /Fisher
|
P
|
Age[n(%)]
>65years old
≤65years old
|
32(31.4)
70(68.6)
|
22(19.6)
90(80.4)
|
3.893
|
0.048
|
Gender[n(%)]
Male
Female
|
76(74.5)
26(25.5)
|
88(78.6)
24(21.4)
|
0.492
|
0.483
|
Address[n(%)]
North
South
|
97(95.1)
5(4.9)
|
109(97.3)
3(2.7)
|
|
0.483
|
Smoke[n(%)]
Yes
No
|
48(47.1)
54(52.9)
|
41(36.6)
71(63.4)
|
2.401
|
0.121
|
Drink[n(%)]
Yes
No
|
32(31.4)
70(68.6)
|
35(31.3)
77(68.7)
|
0.016
|
0.898
|
Category[n(%)]
Initial
Recurrent
|
20(19.6)
82(80.4
|
39(34.8)
73(65.2)
|
6.187
|
0.013
|
Drug resistance[n(%)]
No drug resistance
Single-drug resistance
Multi-drug resistance
|
82(80.4)
12(11.8)
8(7.8)
|
96(85.7)
5(4.5)
11(9.8)
|
3.999
|
0.135
|
Illness course[n(%)]
≤1year
>1year,≤5years
>5years,≤10years
>10years
|
34(33.3)
32(31.4)
11(10.8)
25(24.5)
|
70(62.5)
27(24.1)
8(7.1)
7(6.3)
|
23.067
|
<0.001
|
Pulmonary cavitation[n(%)]
Yes
No
|
74(72.5)
28(27.5)
|
52(46.4)
60(53.6)
|
15.043
|
<0.001
|
Pleural effussion[n(%)]
Yes
No
|
47(46.1)
55(53.9)
|
35(31.3)
77(68.7)
|
4.966
|
0.026
|
Regular anti-tuberculosis [n(%)]
Yes
No
|
63(52.1)
39(41.9)
|
58(51.8)
54(48.2)
|
2.163
|
0.141
|
Advanced antibiotics were used for at lest 1 week[n(%)]
Yes
No
|
65(63.7)
37(36.3)
|
12(21.4)
24(78.6)
|
39.314
|
<0.001
|
Glucocorticoid were used for at lest 2 weeks[n(%)]
Yes
No
|
19(18.6)
83(81.4)
|
12(10.7)
100(89.3)
|
2.698
|
0.100
|
Chemotherapy or immunosuppressants[n(%)]
Yes
No
|
9(8.8)
93(91.2)
|
1(0.9)
111(99.1)
|
|
0.007
|
Invasive operation[n(%)]
Yes
No
|
69(67.6)
33(32.4)
|
81(72.3)
31(27.7)
|
0.556
|
0.456
|
Surgery[n(%)]
Yes
No
|
47(46.1)
55(53.9)
|
34(30.4)
78(69.6)
|
5.609
|
0.018
|
Bacterial infection in the lungs[n(%)]
Yes
No
|
24(23.5)
78(76.5)
|
3(2.7)
109(97.3)
|
21.051
|
<0.001
|
Chronic bronchitis/ COPD/Bronchitis/Asthma[n(%)]
Yes
No
|
19(18.6)
83(81.4)
|
9(8.0)
103(92.0)
|
5.266
|
0.022
|
Silicosis[n(%)]
Yes
No
|
3(2.9)
99(97.1)
|
0(0)
112(100)
|
|
0.107
|
Interstitial lung disease[n(%)]
Yes
No
|
3(3.9)
99(97.1)
|
4(3.6)
108(96.4)
|
|
1.000
|
Hypohepatia[n(%)]
Yes
No
|
37(36.3)
65(63.7)
|
31(27.7)
81(72.3)
|
1.820
|
0.177
|
Renal inadequacy[n(%)]
Yes
No
|
8(6.29)
94(93.71)
|
7(4.90)
105(95.10)
|
0.208
|
0.648
|
Tumor / Hematological disease[n(%)]
Yes
No
|
9(8.8)
93(91.2)
|
3(2.7)
109(97.3)
|
3.808
|
0.051
|
Hypoproteinemia[n(%)]
Yes
No
|
56(54.9)
46(45.1)
|
21(17.9)
91(81.2)
|
30.289
|
<0.001
|
Anemia[n(%)]
Yes
No
|
42(41.2)
60(58.8)
|
20(17.9)
92(82.1)
|
14.107
|
<0.001
|
Diabetes[n(%)]
Yes
No
|
24(23.5)
78(76.5)
|
25(22.3)
87(77.7)
|
0.044
|
0.834
|
Table 3 Multivariate analysis of PTB complicated by pulmonary fungal infection(training dataset, N=214)
Variable
|
β-coefficient
|
S.E
|
Wald
|
Sig
|
Exp(B)
|
95%CI
|
Illness course
|
|
|
13.867
|
0.003
|
|
|
Illness course(1)
|
1.381
|
0.518
|
7.103
|
0.008
|
3.978
|
1.441-10.980
|
Illness course(2)
|
1.430
|
0.667
|
4.599
|
0.032
|
4.180
|
1.131-15.450
|
Illness course(3)
|
2.431
|
0.691
|
12.366
|
<0.001
|
11.368
|
2.933-44.063
|
Pulmonary cavitation
|
1.241
|
0.405
|
9.377
|
0.002
|
3.460
|
1.563-7.656
|
Advanced antibiotics were used for at lest 1 week
|
1.148
|
0.396
|
8.425
|
0.004
|
3.153
|
1.452-6.847
|
Chemotherapy or immunosuppressants
|
3.028
|
1.264
|
5.736
|
0.017
|
20.646
|
1.733-245.934
|
Surgery
|
0.769
|
0.382
|
4.041
|
0.044
|
2.157
|
1.019-4.565
|
Bacterial infection in the lungs
|
1.894
|
0.782
|
5.857
|
0.016
|
6.645
|
1.434-30.799
|
Hypoproteinemia
|
1.801
|
0.593
|
9.222
|
0.002
|
6.054
|
1.894-19.352
|
3.2 Establishment and internal validation of the Model and Nomogram
Then we developed a predictive model for predicting the risk of pulmonary
fungal infection for patients with PTB on the basis of the aforementioned 7 predictors. The OR of predictor entering the model was as follows:1 year<illness course≤5 years,3.978;5years<illness course≤10 years,4.180;illness course>10 year,11.368; pulmonary cavitation, 3.460; advanced antibiotics were used for at lest 1 week,3.153 ; chemotherapy or immunosuppressants,20.646; surgery,2.157;bacterial infection in the lungs,6.645 and hypoproteinemia,6.054. As shown in Figure 1, 2,the predictive model showed good discrimination capability for both training[area under the curve (AUC) =0.860, 95% confidence interval (CI) = 0.811–0.909] and internal validation (AUC =0.884, 95% CI = 0.799–0.970) using bootstrapping (resampling = 1000 times).The sensitivity and specificity of the receiver operating characteristic (ROC) curve were 0.777 and 0.804,respectively. The optimal cutoff was 0.5 according to the ROC curve.In addition, its calibration curves also showed that the probabilities as predicted by the predictive model displayed a satisfied consistence with the actual probability for both training set and internal validation set. (Figure 3,4)
To provide physicians with a quantitative tool for individualized prediction of pulmonary fungal infection, a nomogram was constructed according to multivariable logistic regression (Figure 5). The formula based on the model was presented as follows: Logit(P)=-2.970+1.381*illness course(>year,≤5years)+1.430*illness course(>5years,≤10years)+2.431*illness course(>10years)+1.241*pulmonary cavitation(yes=1;no=0)+1.148*advanced antibiotics were used for at lest 1 week(yes=1;no=0)+3.028*chemotherapy or immunosuppressants(yes=1;no=0)+0.769*surgery(yes=1;no=0)+1.894*bacterial infection in the lungs(yes=1;no=0)+1.801*hypoproteinemia(yes=1;no=0).