Lung Ultrasound to Diagnose Community-Acquired Pneumonia
Lung Ultrasound to Diagnose Community-Acquired Pneumonia
A total of 223 patients (124 males and 99 females) who presented to the ED with suspected CAP were admitted to general or emergency medicine ward. Thirty-one patients (18 men and 13 women) with a median age of 72.2 (range 46–85) years were finally excluded because the interval time between ultrasonography and CXR/CT was more than 12 h or no CT scan was finished. Thirteen patients (6 men and 7 women) with a median age of 69.3 (range 52–79) years refused to participate in the study. One hundred seventy-nine patients were finally included in this study with a median age of 71.5 (range 36–88) years. One hundred and twelve patients (61 men and 51 women) were finally diagnosed with CAP. The final diagnoses of patients without pneumonia were shown in Table 1. There were no significant differences in age or gender between CAP group (112 patients) and non-CAP group (67 patients).
Ultrasonography detected consolidation in 80 patients in CAP group, and did not detect consolidation in any patients in non-CAP group (p<0.001) (Table 2). Focal interstitial pattern was detected in 43 patients in CAP group and three patients in non-CAP group, which was a significant difference between these two groups (p<0.001) (Table 3). There were significant differences between CAP group and non-CAP group in the number of subpleural lesions (1.79±1.73 vs 0.70±0.65; t=4.916, p<0.001) and the number of intercostal spaces with pleural-line abnormalities (5.13±4.47 vs 2.01±1.29; p<0.001).
According to the predominant CT patterns, the CAP patients were further divided into Group A (CT showed consolidation) and Group B (CT showed diffuse ground-glass opacification), and ultrasonography findings were compared between these subgroups. There was no significant differences between Group A (85 patients) and Group B (27 patients) in age (p=0.971) or gender (p=0.513). Ultrasonography detected consolidation in 80 patients of Group A, and did not detect consolidation in any patients of Group B, which was a significant difference between the two groups (p<0.001) (Table 2). Focal interstitial pattern was detected in 33 patients in Group A and 10 patients in Group B, and no significant difference was detected between these two groups (p=0.832) (Table 3). There were significant differences between Group A and Group B in the numbers of subpleural lesions (1.16±1.07 vs 3.85±1.93; p<0.001) and the numbers of intercostal spaces with pleural-line abnormalities (3.14±2.20 vs 11.73±3.69; p<0.001).
ROC curves were used to determine the cutoff values of numbers of subpleural lesions and intercostal spaces with pleural-line abnormalities for diagnosis CAP. Area under the curve (AUC) of subpleural lesions for diagnosis of CAP was 0.693. Youden index was 0.271, and the cutoff value was 2 with a diagnostic sensitivity of 37.5% and specificity of 89.6%. AUC of intercostal spaces with pleural-line abnormalities for diagnosis of CAP was 0.726. Youden index was 0.378, and the cutoff value was 5 with a diagnostic sensitivity of 39.3% and specificity of 98.5%.
Using CT as the gold standard, the diagnosis of CAP based on any one of the four criteria (lung consolidation, or focal interstitial pattern, or ≥2 subpleural lesions, or ≥5 intercostal spaces with pleural-line abnormalities) had a sensitivity of 94.6%, a specificity of 98.5% and a diagnostic accuracy of 96.1%. CXR had a sensitivity of 77.7%, a specificity of 94.0% and a diagnostic accuracy of 83.8% for the diagnosis of CAP. There was significant difference between ultrasonography and CXR for sensitivity (p<0.001) and diagnostic accuracy (p<0.001) but not for specificity (p=0.940) (Table 4).
Results
A total of 223 patients (124 males and 99 females) who presented to the ED with suspected CAP were admitted to general or emergency medicine ward. Thirty-one patients (18 men and 13 women) with a median age of 72.2 (range 46–85) years were finally excluded because the interval time between ultrasonography and CXR/CT was more than 12 h or no CT scan was finished. Thirteen patients (6 men and 7 women) with a median age of 69.3 (range 52–79) years refused to participate in the study. One hundred seventy-nine patients were finally included in this study with a median age of 71.5 (range 36–88) years. One hundred and twelve patients (61 men and 51 women) were finally diagnosed with CAP. The final diagnoses of patients without pneumonia were shown in Table 1. There were no significant differences in age or gender between CAP group (112 patients) and non-CAP group (67 patients).
Comparison of Ultrasonography Findings Between CAP Group and non-CAP Group
Ultrasonography detected consolidation in 80 patients in CAP group, and did not detect consolidation in any patients in non-CAP group (p<0.001) (Table 2). Focal interstitial pattern was detected in 43 patients in CAP group and three patients in non-CAP group, which was a significant difference between these two groups (p<0.001) (Table 3). There were significant differences between CAP group and non-CAP group in the number of subpleural lesions (1.79±1.73 vs 0.70±0.65; t=4.916, p<0.001) and the number of intercostal spaces with pleural-line abnormalities (5.13±4.47 vs 2.01±1.29; p<0.001).
3.2 Comparison of Ultrasonography Findings in CAP Patients With Different CT Patterns
According to the predominant CT patterns, the CAP patients were further divided into Group A (CT showed consolidation) and Group B (CT showed diffuse ground-glass opacification), and ultrasonography findings were compared between these subgroups. There was no significant differences between Group A (85 patients) and Group B (27 patients) in age (p=0.971) or gender (p=0.513). Ultrasonography detected consolidation in 80 patients of Group A, and did not detect consolidation in any patients of Group B, which was a significant difference between the two groups (p<0.001) (Table 2). Focal interstitial pattern was detected in 33 patients in Group A and 10 patients in Group B, and no significant difference was detected between these two groups (p=0.832) (Table 3). There were significant differences between Group A and Group B in the numbers of subpleural lesions (1.16±1.07 vs 3.85±1.93; p<0.001) and the numbers of intercostal spaces with pleural-line abnormalities (3.14±2.20 vs 11.73±3.69; p<0.001).
Comparison of Bedside Ultrasonography and CXR Diagnosis of CAP
ROC curves were used to determine the cutoff values of numbers of subpleural lesions and intercostal spaces with pleural-line abnormalities for diagnosis CAP. Area under the curve (AUC) of subpleural lesions for diagnosis of CAP was 0.693. Youden index was 0.271, and the cutoff value was 2 with a diagnostic sensitivity of 37.5% and specificity of 89.6%. AUC of intercostal spaces with pleural-line abnormalities for diagnosis of CAP was 0.726. Youden index was 0.378, and the cutoff value was 5 with a diagnostic sensitivity of 39.3% and specificity of 98.5%.
Using CT as the gold standard, the diagnosis of CAP based on any one of the four criteria (lung consolidation, or focal interstitial pattern, or ≥2 subpleural lesions, or ≥5 intercostal spaces with pleural-line abnormalities) had a sensitivity of 94.6%, a specificity of 98.5% and a diagnostic accuracy of 96.1%. CXR had a sensitivity of 77.7%, a specificity of 94.0% and a diagnostic accuracy of 83.8% for the diagnosis of CAP. There was significant difference between ultrasonography and CXR for sensitivity (p<0.001) and diagnostic accuracy (p<0.001) but not for specificity (p=0.940) (Table 4).
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