Fig 1.
Measurement of total amount of pleural effusion.
The amount of pleural effusion is calculated from the distance between the parietal and visceral pleura layers by drawing a vertical line (Fig 1).
Fig 2.
Representative figures for hemi-split pleura sign (A, B) and split pleura sign (C, D).
Thickened visceral or parietal pleura on thoracic CT show the “hemi-split pleura sign” (A, B). When both pleura are thickened and separated by effusion, this is defined as the “split pleura sign” (C, D).
Table 1.
Baseline characteristics of the CPPE/Empyema and PPE groups.
Table 2.
Laboratory findings of blood and pleural fluid in the CPPE/empyema and PPE groups.
Fig 3.
Correlation between serum WBC counts and pleural fluid TCC in the CPPE/empyema and PPE groups.
No apparent associations are seen between serum WBC counts and pleural fluid TCC in the CPPE/empyema group (r = -0.134, p = 0.444) and PPE group (r = -0.172, p = 0.382). CPPE: complicated parapneumonic effusion, PPE: parapneumonic effusion, TCC: total cell count, WBC: white blood cell count.
Fig 4.
Correlation between pleural fluid LDH and ADA levels using combined data from the CPPE/empyema and PPE groups.
An intense, strongly positive correlation (r = 0.748, p<0.001) is noted between LDH and ADA levels. ADA: adenosine deaminase, CPPE: complicated parapneumonic effusion, LDH: lactase dehydrogenase, PPE: parapneumonic effusion.
Table 3.
Radiological findings on thoracic CT in the CPPE/empyema and PPE groups.
Fig 5.
Correlations among radiological parameters in both PPE (A-C) and CPPE/empyema groups (D-F).
A significant correlation between total amount of fluid and thickness of the visceral pleura is seen in both CPPE/empyema (r = 0.394, p = 0.019) and PPE groups (r = 0.318, p = 0.03). Similarly, the thickness of visceral pleura and HU (Hounsfield units) value show moderate positive correlations in both groups (CPPE/empyema group: r = 0.454, p = 0.006; PPE group: r = 0.438, p = 0.002). A significant correlation between total amount of pleural fluid and HU value is seen in the PPE group, but not in the CPPE/empyema group.
Table 4.
Multivariate analysis for factors predictive of CPPE/empyema.
Fig 6.
Diagnostic accuracy for CPPE/empyema using two parameters.
Receiver-operator characteristic (ROC) curve using the split pleura sign and total amount of pleural effusion (≥30 mm). The split pleura sign (C) shows 80.6% sensitivity, 74.5% specificity, a positive predictive value of 74.5%, and a negative predictive value of 70.7%, with an area under the curve of 0.775. The presence of both split pleura sign and total amount of pleural effusion (≥30 mm) (D) shows 79.4% sensitivity, 80.9% specificity, a positive predictive value of 75%, and a negative predictive value of 84.4%, with an area under the curve of 0.801. A: pleural effusion ≥30 mL; B: pleural effusion ≥30 mL or split pleura sign; C: split pleural sign; D: total amount of pleural effusion ≥30 mL and split pleura sign.
Table 5.
Diagnostic accuracies of the two risk factors for CPPE/empyema.