Patients aged 18 years and older diagnosed with symptomatic SARS-CoV-2 infection at Verona University Hospital during the period 29 February–25 April 2020 were consecutively screened for inclusion in the study. A local registry of patients with COVID-19 was designed at the beginning of the pandemic in order to collect clinical data (ClinicalTrials.gov NCT04497194). The study protocol was approved by the institutional review board (Ethics Committee for Clinical Experimentation of Verona and Rovigo) and informed consent was provided by all study participants. All procedures were in accordance with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Laboratory-confirmed SARS-CoV-2 infection was diagnosed from respiratory samples by real-time multiplex reverse transcription polymerase chain reaction for simultaneous detection of three different SARS-CoV-2 targets (E, N and RdRP genes) using Allplex 2019-nCoV assay kit (Seegene, Seoul). Patients with no microbiological confirmation of SARS-CoV-2 and patients who did not complete the follow-up were not included in the study. Specifically, three hospitalised patients with negative swabs admitted with symptoms and imaging suggestive of COVID-19 and 83 patients who died during hospitalisation were excluded from the analyses. No deaths were recorded during the study follow-up.
Data collected included age, sex, ethnicity, comorbidities (e.g. hypertension, cardiovascular disease, respiratory disease, diabetes, cancer and renal impairment), body mass index (BMI) > 25, chest X-ray results, hospital admission, antiviral and antibiotic treatment, and need for primary care visits. Length of hospital stay and need for ICU admission and orotracheal intubation were recorded among inpatients.
According to the Centers of Disease Control and Prevention (CDC) clinical guidance for COVID-19 management, patients were hospitalised on a case-by-case basis and admission criteria included hypoxia, radiological evidence of viral pneumonia and need for oxygen support as well as potential for deterioration [4, 5]. Patients with mild clinical presentation who did not require hospitalisation were initially assessed at the hospital and discharged with indication of clinical monitoring and home self-isolation or directly managed at home by primary care physicians. During the study period, regional standard of care of COVID-19 consisted of hydroxychloroquine (HCQ) and/or lopinavir/ritonavir (LPV/r). Inpatients were discharged on the basis of improvement of respiratory symptoms, irrespective of positivity of nasal swab.
Four outcomes were assessed: (1) the Barthel index of activities of daily living, (2) an adapted version of the St. George’s Respiratory Questionnaire tailored to patients with COVID-19 (aSGRQ), (3) patient’s symptoms (cough, breathlessness, fatigue, anosmia, dysgeusia, myalgia) and (4) WHO Clinical Progression Scale (WHO-CPS). Patients’ subjective perception of general health was also recorded on a 1 to 5 scale (1 = very poor, 2 = poor, 3 = fair, 4 = good, 5 = very good).
Barthel index, aSGRQ and perception of general health were assessed at three time points: prior to the onset of COVID-19 (T0, based on retrospective patients’ recollection), at the time of COVID-19 diagnosis (TD) and after a median time of 6–8 weeks (43 days, Q1–Q3, 37–48) from the onset of symptoms (T1, follow-up). WHO-CPS was assessed at TD and T1. Patients reporting at least one of the aforementioned symptoms at T1 (symptomatic patients) were rescheduled for a second phone interview (T2) to investigate persistence of symptoms after 4–6 weeks from T1 (median time 34 days, Q1–Q3, 34–37). Maximum follow-up period was 12–14 weeks from the onset of symptoms. The study design is summarized in Supplementary Fig. 1.
Questionnaires were administered via in-person or phone interviews run by a nurse or a doctor involved in the care of patients with COVID-19. A structured case report form for data collection and training for conducting the interviews were provided to the healthcare workers involved in the study.
The Barthel index (BI) consists of a 10-item ordinal scale measuring patients’ functional independence (e.g. self-care, sphincter management, transfers and locomotion) . Total possible scores ranged from 0 to 100, with lower scores indicating increased disability (less than 20, totally dependent; 20–39, very dependent; 40–59, partially dependent; 60–79, minimally dependent; 80–100, independent). The adapted Saint George Respiratory Questionnaire (aSGRQ) was based on SGRQ and its short version (SGRQ-C) that measure health impairment in respiratory diseases, including infections such as tuberculosis and aspergillosis [7,8,9,10]. The aSGRQ excluded symptom characteristics of asthma (e.g. wheezing) and questions related to social activities since the study was run when patients were self-isolated at home. The aSGRQ included a symptom component (questions 1–3) assessing patients’ frequency of respiratory symptoms (e.g. cough, sputum production, breathlessness) and an activity component (questions 4–6), addressing disturbances to daily activities (including perception of chest condition as a problem, occurrence of breathlessness while talking, getting washed or dressed, or walking around the house; sleep disturbances caused by chest issues, and getting easily exhausted). Higher SGRQ scores indicated increased health impairment. In order to adapt SGRQ for patients with COVID-19, we adjusted the weighting system, excluding from the total the weights of the unused items. A total score (1410.9) and two-component scores (symptoms, 446.5 and activity, 964.4) were calculated according to a predefined algorithm . Individual scores were calculated using the algorithm suggested, dividing the sum of all items by the total weights of each scale and then multiplying by 100.
The WHO-CPS indicated mild (ambulatory—no symptoms, 1; no limitation of activities, 2; limitation of activities, 3), moderate (hospitalized—no oxygen therapy, 4; oxygen by mask or nasal prongs, 5) and severe disease (oxygen by non-invasive ventilation or high flow, 6; intubation and mechanical ventilation, 7; mechanical ventilation with SpO2/FiO2 < 200 or vasopressors, 9; mechanical ventilation with pO2/FiO2 < 150 and vasopressors, dialysis or extracorporeal membrane oxygenation [ECMO], 9) .
For continuous variables, mean and standard deviation or median and IQR were calculated. For nominal variables, count and percentages were used. Wilcoxon–Mann–Whitney test was used for comparing independent groups. The association between categorical variables was assessed using Fisher’s test. A multivariate logistic regression model was used to investigate the association between hospitalisation and demographic variables and comorbidities. Ordinal multilevel multivariate logistic regression with a random component was used to identify factors associated with the ordinal distribution of outcome measures such as Barthel Index, aSGRQ score and WHO-CPS over time. Proportional odds (PO) ordinal multilevel logistic regression is a well-characterised method of analysing data where a dependent variable (Y) that takes ordered integer values is modelled as a function of a vector X of covariates. Ordinal logistic regression fits ordered logit models of ordinal variable and provides an estimate of a set of predictors association. In order to account for the longitudinal nature of the study, the variable time was added to the model and a random effect was added to account for repeated measures at the subject level. Age, gender, comorbidities, hospitalisation and ICU admission were used as predictors of the outcome measures.
Predictors associated with the outcome variable with a probability < 0.05 were considered significant. To investigate symptoms duration, the product-limit method (Kaplan and Meier) with 95% CI was used. Comparison of symptoms between inpatients and outpatients was performed using the log-rank test analysing each symptom separately. Analyses were carried out using Stata® Version 16.1 (College Station, TX: StataCorp LP).