Association of radiologic findings with mortality in patients with avian influenza H7N9 pneumonia

Abstract

Background: The novel H7N9 virus causes severe illness, including pneumonia and acute respiratory distress syndrome, with high rates of mortality. We investigated the association of initial radiologic characteristics obtained at admission with clinical outcomes in patients with avian influenza H7N9 pneumonia.

Methods: Demographics, comorbidities, clinical findings, radiologic appearance and scores of the affected lung parenchyma were compared between survivor group (n = 15) and mortality group (n = 7). Two radiologic scores were calculated, one using chest radiography and one using CT. Follow-up CT scans at discharge were analyzed in 12 patients of the survival group.

Results: All the patients in mortality group developed acute respiratory distress syndrome and required mechanical ventilation, while in the survival group 33% (5/15) developed acute respiratory distress syndrome (P<0.05) and 27% (4/15) required mechanical ventilation (P<0.05). The mean radiographic and CT scores of the mortality group were 50% higher compared to the survival group (P<0.05). ROC analysis revealed an area under curve of 0.738 for the radiographic score with an optimal cutoff value of a score of 19 for prediction of mortality, with a sensitivity of 71% and a specificity of 67%, and an area under curve of 0.833 for the CT score with an optimal cutoff value of a CT score of 21 for prediction of mortality, with a sensitivity of 86% and a specificity of 73%. The mean CT score of the affected lung parenchyma at discharge was 30% lower than the initial CT examination (P<0.05).

Conclusion: High initial radiologic score is associated with mortality in patients with avian influenza H7N9 pneumonia.

Figure 1. The schematic of CT scoring system.

Schematic coronal representations of zones, extent of ground-glass opacity and consolidation on an axial image, and a sample scoring on an axial CT image. Schematic coronal representation of zones (A) evaluated in the lungs of patients with H7N9 infection shows upper zones which are above the carina, middle zones between the carina and the inferior pulmonary vein, and lower zones which are below the inferior pulmonary vein. Schematic representation of the extent of ground-glass opacity (GGO) and consolidation (CO) on an axial image (B) which were determined using the modified Grieser system. Points from all zones were added for a cumulative score, with value ranging from 0 to 72. A sample scoring on an axial CT image (C) of a 52-year-old woman from mortality group demonstrates a total score of 18, calculated as 3 (consolidation, solid arrow) ×4 (>75% distribution in middle zone of the right lung) +2 (ground-glass opacity, open arrow) ×1 (<25% distribution in middle zone of the right lung) +2 (ground-glass opacity, open arrow) ×2 (25–50% distribution in middle zone of the left lung).

Figure 2. A 74 year old male patient with H7N9 pneumonia from mortality group.

Chest radiograph with score of 28 shows bilateral patchy consolidations and ground glass opacities.

Figure 3. A 67 year old male patient with H7N9 pneumonia from survival group.

Chest radiograph with score of 4 shows patchy consolidations and ground glass opacities in the left middle and lower zones.

Figure 4. ROC analysis of the chest radiographic score for prediction of mortality.

N = 22; AUC  = 0.738.

Figure 5. A 52 year old female patient with H7N9 pneumonia from mortality group.

CT images with score of 38 show ground glass opacity and consolidation in the middle (A) and the lower zones (B). There is a small amount of right pleural effusion.

Figure 6. A 53 year old male patient with H7N9 pneumonia from survival group.

CT images with CT score of 18 show ground glass opacity mostly in the upper zones (A) and consolidation in the lower zones (B).

Figure 7. ROC analysis of the CT score for prediction of mortality.

N = 22; AUC = 0.833.