Material and methods
This study received ethical approval from the Tehran University of
Medical Sciences, Tehran, Iran. All participants gave written informed
consent, and the study was carried out following the Declaration of
Helsinki.
Patient selection
Subjects of the study were children with confirmed SARS-CoV-2 pneumonia
by real-time RT-PCR (admitted between 07 March and 10 June 2020) in
Children’s Medical Center, an Iranian referral hospital who underwent
the detection of peripheral blood lymphocyte subsets. The following
information on each patient was extracted from electronic medical
records: age, sex, underlying disease, intensive care unit (ICU)
admission, need for invasive mechanical ventilation, laboratory
findings, chest computed tomography (CT), and mortality. Chest CT scan
was reported by an expert radiologist, and abnormal CT finding was
considered if typical CT imaging features for COVID-19 including
peripheral, bilateral, ground-glass opacification with or without
consolidation or visible intralobular lines, multifocal ground-glass
opacification or rounded morphology with or without consolidation or
visible intralobular lines, or reverse halo sign or other findings of
organizing pneumonia were reported
(Simpson, Kay et al. 2020). On admission,
severe illness was defined according to the following criteria: (1)
breathing rate ≥30 times/min; (2) pulse oximeter oxygen saturation
(SpO2) ≤93% at rest; and (3) ratio of the partial
pressure of arterial oxygen (PaO2) to the fraction of
inspired oxygen (FiO2) ≤300 mmHg
(Wang, Nie et al. 2020).