A retrospective study from Turkey has defined four stages of Covid-19 pneumonia based on the extent of lung involvement as seen on High Resolution Computed Tomography (HRCT) scan of the lungs.¹

This study, published in the journal Medicine, retrospectively analyzed HRCT scans of 130 patients, aged 25 to 87  years, with suspected Covid-19 pneumonia or a history of close contact with an infected person between April 2020 and December 2020. Patients with a history of contact but no symptoms underwent simultaneous RT-PCR and/or HRCT lung. Seventy-one of the 130 patients were RT PCR positive, while 59 were RT PCR negative.

The findings on HRCT in patients with Covid-19 pneumonia were categorized into four stages according to the pattern of the lung damage. Stages I, II and III were further subgrouped into A and B.

Analysis revealed that Stage 1 patients (39.2%) were clinically asymptomatic but had history of exposure and tested positive on RT PCR. While no radiological findings were seen in Stage 1A patients, lung inflammation was detected as mosaic perfusion (mosaic attenuation) as a single focus or multiple foci without any lung parenchymal architectural distortion on HRCT in Stage 1B patients.

Stage II patients (39.2%) were mildly symptomatic but not all were positive on RT PCR. However, the inflammation had started to progress and lung inflammation due to Covid-19 infection was evident as ground glass opacities (GGO), single focus in Stage IIA and with multiple foci in Stage IIB. Micronodular infiltration was seen in Stage IIA, which became diffuse in Stage IIB patients.

Stage III patients (20%) had moderate disease and almost all had symptoms. Half of them had positive RT PCR. Progressive infection in the form of pneumonia was detected in HRCT as consolidation with multiple foci in Stage IIIA. Mild pleural and/or pericardial effusion was present along with the consolidation in Stage IIIB patients.

Stage IV patients (1.53%) showed the most severe lung damage with massive consolidation with smoothly thickened interlobular septa in a crazy paving pattern. Massive pleural/pericardial effusion were also noted. These patients needed intensive care and were intubated.

This study has described lung involvement in the initial stages of the disease (Stage IIA). It also underscores the need for early detection of lung infection and close follow-up of the patients. Timely initiation of treatment prevents complications with favorable clinical outcomes in the form of reduced need for hospitalization and quicker resolution of the disease. In this study, patients in stage IIA showed comparable response to treatment as stage I patients. whereas patients in Stage III and IV required prolonged treatment.

The authors concluded that “The novel classification of HRCT findings will be helpful to early diagnosis of the disease, time saving and eventually cost-effective.”

Reference

1. Fayadoglu M, et al. Analysis and classification of radiological results and epidemiology of patients with COVID-19 pneumonia. Medicine (Baltimore). 2021 Dec 23;100(51):e28154. doi: 10.1097/MD.0000000000028154.