Viral Pneumonia Requiring Differentiation from Acute and Progressive Diffuse Interstitial Lung Diseases

Ishiguro, Takashi; Kobayashi, Yasuhito; Uozumi, Ryuji; Takata, Naomi; Takaku, Yotaro; Kagiyama, Naho; Kanauchi, Tetsu; Shimizu, Yoshihiko; Takayanagi, Noboru

The present study was associated with several limitations. First, because this is a non-randomized observational study, the level of confidence was reduced. Second, this study was carried out in a single center, and the results may not be applicable to other settings. It is noteworthy that our institution has about 10 specialist physicians licensed by the Japan Respiratory Society. These physicians judged the need for BAL, and thus, there was bias in terms of the patients who underwent BAL. In addition, the requirement for hospitalization was a major criterion for entry into this study. This could potentially induce a spectrum bias in which only the most severe cases were enrolled in the study. Third, there may be incorporation bias in that the review panel determined that the final diagnosis was more likely to classify cases as viral pneumonia when fever and sore throat were present. Fourth, we did not investigate antibody titers against viruses in the acute and convalescent phases; thus, the number of cases of viral pneumonia might have been underestimated (32) . Fifth, the multidisciplinary diagnoses were made without video-assisted thoracoscopic surgery in most cases; thus, the pathological findings may not have been fully evaluated. Sixth, some viral infections may have been missed in this study because only a limited number of viruses were screened in the assay. Finally, the possibility of detecting viruses from the upper respiratory tracts cannot be denied when using the BAL technique. To avoid this concern, a well-designed, prospective study is needed in which samples are obtained only from the lower respiratory tract, for example, via intubation or with the use of a protected specimen brush.