Prognostic relevance and inter-observer reliability of chest-imaging in pediatric ARDS: a pediatric acute respiratory distress incidence and epidemiology (PARDIE) study

Abstract

Purpose: Definitions of acute respiratory distress syndrome (ARDS) include radiographic criteria, but there are concerns about reliability and prognostic relevance. This study aimed to evaluate the independent relationship between chest imaging and mortality and examine the inter-rater variability of interpretations of chest radiographs (CXR) in pediatric ARDS (PARDS).

Methods: Prospective, international observational study in children meeting Pediatric Acute Lung Injury Consensus Conference (PALICC) criteria for PARDS, which requires new infiltrate(s) consistent with pulmonary parenchymal disease, without mandating bilateral infiltrates. Mortality analysis focused on the entire cohort, whereas inter-observer variability used a subset of patients with blinded, simultaneous interpretation of CXRs by intensivists and radiologists.

Results: Bilateral infiltrates and four quadrants of alveolar consolidation were associated with mortality on a univariable basis, using CXRs from 708 patients with PARDS. For patients on either invasive (IMV) or non-invasive ventilation (NIV) with PaO₂/FiO₂ (PF) ratios (or SpO₂/FiO₂ (SF) ratio equivalent) > 100, neither bilateral infiltrates (OR 1.3 (95% CI 0.68, 2.5), p = 0.43), nor 4 quadrants of alveolar consolidation (OR 1.6 (0.85, 3), p = 0.14) were associated with mortality. For patients with PF ≤ 100, bilateral infiltrates (OR 3.6 (1.4, 9.4), p = 0.01) and four quadrants of consolidation (OR 2.0 (1.14, 3.5), p = 0.02) were associated with higher mortality. A subset of 702 CXRs from 233 patients had simultaneous interpretations. Interobserver agreement for bilateral infiltrates and quadrants was "slight" (kappa 0.31 and 0.33). Subgroup analysis showed agreement did not differ when stratified by PARDS severity but was slightly higher for children with chronic respiratory support (kappa 0.62), NIV at PARDS diagnosis (kappa 0.53), age > 10 years (kappa 0.43) and fluid balance > 40 ml/kg (kappa 0.48).

Conclusion: Bilateral infiltrates and quadrants of alveolar consolidation are associated with mortality only for those with PF ratio ≤ 100, although there is high- inter-rater variability in these chest-x ray parameters.

Keywords: ARDS; Chest radiograph; Diagnostic accuracy; Inter-rater variability; Outcome.

Fig. 1

Relationship between ICU mortality and chest X-ray (CXR) infiltrates stratified by initial PF ratio (or SF ratio equivalent) and ventilation type (invasive or noninvasive mechanical ventilation) at PARDS diagnosis. 708 subjects from the whole PARDIE cohort had a CXR available (185 unilateral/523 bilateral infiltrates) at PARDS diagnosis. Bars represent number of cases per initial PF ratio and ventilation type. Whiskers represent $\pm$ 1 standard error around the point estimate for mortality (squares). NIV, noninvasive ventilation; IMV, invasive mechanical ventilation; PF: ratio of partial pressure of oxygen (PaO₂) to fractional concentration of oxygen (FiO₂), PO₂/FiO₂ ratio

Fig. 2

Subjects and ICU mortality stratified by initial PF ratio at PARDS diagnosis combined with chest X-ray infiltrates (uni/bilateral). 708 subjects from the whole PARDIE cohort had a CXR available (185 unilateral/523 bilateral infiltrates) at PARDS diagnosis. Bars represent number of cases per initial PF ratio. Whiskers represent ± 1 standard error around the point estimate for mortality (squares). Mortality was substantially higher for patients with PF ≤ 100 and bilateral infiltrates, compared to all other combinations of infiltrates and PF ratios. This includes patients on either noninvasive ventilation or invasive mechanical ventilation. PF: ratio of partial pressure of oxygen (PaO₂) to fractional concentration of oxygen (FiO₂), PO₂/FiO₂ ratio