DIFFERENTIATING SWINE FLU FROM OTHER VIRAL PNEUMONIA ON CHEST COMPUTED TOMOGRAPHY WITH EMPHASIS ON ANTERIOR PERICARDIAL THICKENING.

Rajesh Ghosh; Nilu Malpani Dhoot; Usha goenka; Srijita Ghosh; Somali Ghosh

doi:10.5455/ajdi.20210504082116

Abstract
OBJECTIVE: To establish utility of anterior pericardial thickening for
Influenza A Hemagglutinin 1 Neuraminidase 1(H1N1) on CT thorax.
METHODS: A prospective study was carried out on 385 patients with a
positive comprehensive viral panel test from December 2018 to January 2020.
Of this, 102 patients positive for H1N1 formed the study group. The control
group consisted of the remaining 248 patients with a positive comprehensive
viral panel other than H1N1. Thirty-five patients were excluded from the study,
as they were positive for two or more viruses. The CT scan of these patients
was evaluated for various morphological findings indicating viral infection and
the presence of the "anterior pericardial" (AP) sign. The AP sign was
considered positive when the pericardium was thickened focally or diffusely,
with thickness more than 4mm.
RESULTS: Ground Glass Opacity (GGO) was the most prevalent finding in
viral pneumonia. The AP sign, when present, could identify 72.5% of patients
with Swine flu (SF). It was absent in 49% of patients with other viral (OV)
infections and was an effective assertor of SF (p<0.0004). The sign had a
specificity of 48%, a positive predictive value of 36%, a negative predictive
value of 81%, and an accuracy of 55.4%.
CONCLUSION: The absence of AP sign-on HRCT chest has a high negative predictive value for SF. It can be used as an additional diagnostic tool in differentiating SF from other OV infections on HRCT.

Key words: Swine flu, viral pneumonia, CT chest, pericardial thickening