Khamapirad radiologic criteria as a predictor of pneumonia's bacterial etiology

Dear Editor,

As the authors propose in their study, the chest X-ray has a significant role in the differentiation and identification of the bacterial etiology of pneumonia.¹ The main findings of chest X-ray suggesting a pathology of bacterial origin are: lobar or segmental consolidation, pneumatocele and the presence of a pulmonary abscess. These findings are significantly associated with a typical bacterial infection.¹

Despite this, in most cases typical bacterial pneumonia – mainly in the early stages of the disease – is not accompanied by those classic radiographic patterns.² On the other hand, some viral infections are capable of showing similar radiological patterns; for example, a consolidation pattern can be observed in an adenovirus infection.² This scenario is a barrier to the etiological diagnosis based solely on the chest X-ray. Virkki et al., in a study of 215 children with Acquired Pneumonia in the Community (NAC), of which 62% had bacterial etiology and the rest were exclusively viral, found that the alveolar infiltrates had a sensitivity of 72% and a specificity of 51% to identify a bacterial etiology.³ They also reported that the specificity increased up to 85% when the alveolar infiltrates were of the lobar type, mainly in children under 2 years of age. The interstitial infiltrates, on the other hand, failed to adequately differentiate between viral and bacterial pneumonia. The hyperaerial, atelectasis and small pleural effusion also had no significance for this differentiation.²

In contrast, Moreno et al. found in children with NAC a great correlation of the interpretation of chest radiographs in those read both by a pediatrician and by radiologists, which translated into excellent diagnostic accuracy. The radiological scale they used was the Khamapirad scale, which showed a sensitivity of 100% (95% CI: 90–100%), specificity of 98% (95% CI: 93–99%), a positive predictive value of 96% (95% CI: 85–99%), and a negative predictive value of 100% (95% CI: 96–100%) to predict bacterial pneumonia with a simple chest plaque X-ray.⁴ This study strongly reinforces the usefulness of an X-ray for the etiological diagnosis of bacterial pneumonia as well as its usefulness to rule it out when the result is negative.

In addition to this, Torres et al., also using the Khamapirad scale, found in their study of children hospitalized by NAC a sensitivity of 100% (95% CI: 83–100%), specificity of 94% (95% CI: 88–97%), a positive predictive value of 77% (95% CI: 58–90%), and a negative predictive value of 100% (95% CI: 96–100%) to predict bacterial pneumonia.⁵ This corroborates the findings of all the aforementioned authors and shows us the capacity of bacterial etiological identification through the use of a chest X-ray and an adequate scale.⁵ Ultimately, Guanoluisa and Geovanny obtained a kappa index of 0.87 which represents a very good accordance. In this study, they also used the Khamapirad scale to evaluate chest radiographs of children.⁶

Based on the findings of the study by Andrade et al., and in addition to the reviewed literature, it can be concluded that the use of the Khamapirad scale on a chest radiograph to identify the bacterial etiology of pneumonia is quite accurate, both for the confirmation of the etiology and to dismiss it according to the radiologic score. The use of an evaluation score like that of Khamapirad allows a better sensitivity and specificity of the chest X-ray. In this way, it is recommended that these criteria be introduced to physicians in order to improve the etiological identification and therapeutic management of pediatric patients with a diagnosis of pneumonia, especially in areas where pediatricians are not found.

Funding

This letter to the editor was funded by the author itself.

Conflicts of interest

The author declares no conflicts of interest.

Acknowledgement

The author would like to thank Dr. Juan Francisco Sanchez (Lima, Perú) for all the help and advice given during the development of this letter.