COVID19 Versus H1N1: Radiological Challenge During Next Influenza Season Rising
Condition: COVID
Study type: Observational

Summary: 
      Background: Till the moment of editing this paperwork, WHO announced that there is no
      specific drugs or vaccines for treatment or prophylaxis of COVID-19. Additionally during the
      global gradual unlocking of community restrictions, WHO warned form another wave of the
      disease during the next few months. So clinicians and radiologists during this second wave
      would face great challenges in differentiation between COVID-19 and other virulent influenza
      viruses, mainly H1N1.

      Objective: to establish comparative radiological study between COVID19 and H1N1 to find
      differentiating criteria that would help during their expected clinico-laboratory and
      radiological overlap in next Influenza season.

      Material and methods: Retrospective study was including 130 patients; 65 COVID-19 patients
      and 65 H1N1 patients. HRCT findings to be analyzed by three expert consultant radiologists.
    

Detailed description: 
      A. Study population and medical records review:

      Inclusion criteria: 65 COVID-19 and 65 H1N1 patients to be enrolled. Exclusion criteria: (1)
      Degraded quality of CT scans due to patient unavoidable tachypnea with respiratory motion
      artifacts. (2) Unremarkable CT scans were also excluded. (3) Past history of large airway
      disease, asthma, COPD or bronchiectasis. (4) Patients with secondary bacterial infection.

      B. CT scanning and parameters:

      CT examinations conducted using multiple MDCT machines including: GE LightSpeed Plus 4 slice
      CT scanner (USA), Philips Brilliant-16 (USA), Siemens SOMATOM Emotion 16 and Siemens SOMATOM
      Sensation 64 (Germany), Toshiba Aquilion 64 and Toshiba Aquilion CXL/CX 128 (USA).

      CT Scanning parameters : Slice thickness: 1 - 1.25 mm. Volumetric HRCT table speed with least
      cycles of breath holds as possible. Tube rotation: 0.6-0.9 second. Detector Collimation 1 mm.
      Helical mode (volumetric HRCT). kVp and mA per slice: 120 - 130 kVp and 200-400 mA, according
      to the type of MSCT machine used, the weight of the patient and the clinical indication.

      C. CT analysis:

      CT images to be assessed by three consultant radiologists (having long time experience in
      chest imaging). Image analysis in axial, sagittal and coronal planes done using both maximum
      intensity projection (MIP) and minimum intensity projection (Min-IP) reconstructions. The
      following CT features to be compared between each pathological process:

      A. Site of the pathology: unilateral or bilateral - focal, multi-focal or diffuse.

      B. Mosaic pattern; including ground glass opacities (GGO), mosaic perfusion, air trapping and
      "head cheese pattern".

      C. Reticular pattern; including interlobular septal thickening, "crazy paving pattern",
      bronchial wall thickening, mucous plugging, traction bronchiectasis/bronchiolectasis and
      honeycombing.

      D. Nodular pattern; including GG nodules and solid nodules; including solid nodules with
      "halo sign" and tree in bud nodules.

      E. Relevant CT findings: including pleural, pericardial and nodal lesions.

      D. Statistical analysis:

      The prevalence of HRCT findings estimated as the percentage of patients showing each criteria
      or abnormality.
    

Observational model: Case-Crossover
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        130 patients; 65 patients known with COVID19 (registered during the period from February
        till May 2020) and 65 patients known with H1N1 (registered during the period from January
        2010 till January 2020).