Procedures
Clinical data including demographic characteristics (age, gender, smoking status), antiviral treatment (hydroxychloroquine, favipiravir, convalescent plasma, steroids), chest tomography results and complication development during hospitalization were obtained from the hospital electronic record system. Patients were classified into 2 groups: ICU patients (followed in the ICU due to COVID-19) and non-ICU patients (hospitalized due to COVID-19 but followed in the pulmonary ward).
Patients were invited to the follow-up visit, by healthcare professionals, by telephone. All participants were consulted face to face by an investigator; asked to complete a questionnaire to assess their health status (Short Form-36, SF-36); and asked for persistent symptoms such as dyspnea, fatigue, muscle weakness etc. A trained physiotherapist performed a 6-min walking test to assess functional exercise capacity. The pulmonary function test was performed in the Pulmonary Functional Centre in University of Health Sciences, Dr. Suat Seren Chest Disease and Thoracic Surgery Teaching and Research Hospital according to American Thoracic Society and European Respiratory Society spirometry standardizations20.
Chest high-resolution computed tomography (HRCT) was performed at the end-inspiration in supine position, 1.25 mm section thickness and 0.625 mm reconstruction with high resolution. An experienced radiologist cross-compared HRCT images during hospital stay and follow-up HRCT images. If a participant had more than one HRCT, final chest images were included in the comparison. Both lungs were divided into 5 lobes in accordance with normal anatomical structure. Each lung lobe was given a score according to the following criteria; 0, no involvement; 1, less than 5% involvement; 2, 5-25% involvement; 3, 25-50% involvement; 4, 50-75% involvement; 5, more than 75% involvement. The total CT score was calculated semi-quantitatively with the sum of the scores of the five lobes21.
The SF-36 test is a 36-item self-reported survey of quality of life. SF-36 contains eight categories that assess physical functioning, social functioning, role limitation due to physical and emotional problems, general and mental health, bodily pain and vitality. Each category is scored from 0 (worst) to 100 (best) with higher scores showing better quality of life22. The translated and validated version of SF-36 was used for the study23.
The primary outcome was the percentage of patients with lung involvement in the 6-month follow up CT scan.
Secondary outcomes were exercise capacity (distance of 6-min walking test), pulmonary function tests and health state scores at the follow up visit.