Table 1.

Proposed clarified definitions for World Health Organization defined standardized interpretation of pediatric frontal chest radiographs in pneumonia epidemiological studies

Quality	Uninterpretable	Features of the image are not interpretable with respect to presence or absence of consolidation or pleural effusion without additional images.
	Suboptimal	Features allow interpretation of consolidation and pleural effusion, but not of other infiltrates or findings.
	Adequate	Features allow confident interpretation of consolidation and pleural effusion as well as other infiltrates.
Classification of findings	Significant pathology	Refers specifically to the presence of consolidation, infiltrates or effusion.
	Endpoint consolidationa	A dense or confluent opacity that occupies a portionb or whole of a lobe or the entire lung, that may or may not contain air bronchogramsc.
	Other (non-endpoint) infiltrates	Linear and patchy opacities (interstitial infiltrate) in a lacy pattern, featuring peribronchial thickening and multiple areas of atelectasis; it also includes minor patchy infiltrates that are not of sufficient magnitude to constitute endpoint consolidation, and small areas of atelectasis that in children may be difficult to distinguish from consolidation.
	Pleural effusion	Presence of fluid in the lateral pleural space between the lung and chest wall that is spatially associated with a pulmonary parenchymal infiltrate (including other infiltrate) or has obliterated enough of the hemithorax to obscure any infiltrate; in most cases, this will be seen at the costo-phrenic angle or as a layer of fluid adjacent to the lateral chest wall; this does not include fluid seen in the horizontal or oblique fissures.
Conclusionsd	Primary endpoint pneumonia	The presence of consolidation or pleural effusion, as defined above.
	Other infiltrate	The presence of other (non-consolidation) infiltrates as defined above in the absence of a pleural effusion.
	No consolidation/infiltrate/effusion	Absence of consolidation, other infiltrates or pleural effusion.

^aThe choice of the term “endpoint” refers to this being the endpoint of interest for trials of bacterial vaccines against pneumonia

^b“Portion of a lobe” means an opacity with the smallest diameter greater or equal to the size of a posterior rib and one adjacent rib space at the same level as the opacity. Where the opacity is irregular in shape (e.g., wedge-shaped), use the maximum short-axis diameter (the largest diameter perpendicular to the line of maximum diameter of the opacity)

^cIn the presence of any visible adjacent opacity, a silhouette sign, where the length of loss of an anatomical border is greater or equal to the size of a posterior rib and one adjacent rib space at the same level, is considered to indicate consolidation. A silhouette sign of this size without a visible adjacent opacity is considered other infiltrate

^dRefers to the presence of these conclusions in the opinion of a panel of trained readers using the available World Health Organization defined reference materials and methods