Discussion
Our study describes relatively mild and limited respiratory consequences of COVID-19 in our group of children. There are several results from our research. First, we found a relatively low risk of structural and/or functional abnormalities of the respiratory tract and clinical remission usually occurred within several months.
Second, we recognized four subgroups of respiratory post-COVID syndrome with different symptomatology in the studied cohort. Besides the standard post-COVID group, “sporty” subgroup was represented by children used to high-intensity physical activities. These subjects sensitively identified worsening in their physical performance, and their results were usually normal. This group is very probably under-reported due to observer bias. Children with no regular sports activity could miss discrete symptoms exertional dyspnea without regular physical activity. The third subgroup denotes probable incipient bronchial asthma. COVID-19 is not a potential trigger but may coincide with this frequent chronic diagnosis. Furthermore, the focused attention of parents on respiratory symptoms in children after COVID-19 may accelerate early examination by a pulmonologist. There was usually positive family history, atopic history, positive allergy panel, and an excellent response to anti-asthma treatment. This group could be over-reported due to detection bias by pulmonologists. The fourth subgroup includes „polymorphous” post-COVID with a wide variety of symptoms (headache, concentration deficiency, anxiety, hair loss, chest pain, cough, dyspnea, anxiety, tachycardia) which were noticed apart from the monitored respiratory symptoms. Adolescent girls highly predominate. Previous mental health problem in them or their close relatives was found in 60%. This group reflects the complex consequences of COVID-19 pandemic in a very fragile age. In our study this group is very probably under-reported due to selection bias. Variety of their non respiratory problems may lead to referral to another specialist and not to a pulmonologist.
Our results are in accordance with other published work designed as case series. These studies confirmed existence of pediatric post-COVID syndrome and reported diverse symptoms and infrequent occurrence. The first paper on post-COVID-19 syndrome was published by Ludgvisson et al. in November 2020. They collected data from parental reports of five Swedish children with persistent symptoms lasting two months or more after acute COVID infection. Parents contacted authors on an Internet-based social media forum. These children’s symptoms lasted for 6-8 months after their clinical diagnoses of COVID-19 and included fatigue, dyspnea, cardiac palpitations, chest pain, headache, muscle weakness, dizziness, and sore throat. Subsequently, Buonsenso et al. published a cross-sectional study in which 129 children aged 6–16 years diagnosed with COVID-19 between March and November 2020 were interviewed by phone or in an outpatient clinic.
More than one-third reported one or two lingering symptoms four months or more after COVID-19 infection, and a further one-quarter had three or more symptoms. Insomnia, fatigue, muscle pain, and persistent cold-like complaints were common. In a prospective cohort study of Monteni et al., about 1.8% of 1379 children experienced symptoms for at least 56 days after acute COVID, according to data reported by adult proxy via mobile application Radtke et al. compared in a longitudinal cohort study the occurrence of at least one symptom lasting beyond 12 weeks in seropositive and seronegative children (4% vs 2%). Parents reported symptoms via an online questionnaire. The most common complaints included fatigue, difficulty concentrating, and increased sleepiness. Brackel et al. conducted a Dutch national survey on 89 children with long COVID identified by pediatric departments. The most frequent symptoms comprised fatigue, dyspnea, and concentration difficulties; authors described in detail a case series of six children.
To our knowledge, our work is a first prospectively planned study focused on respiratory aspects of pediatric post-COVID. Our data suggest lower risk of functional lung impairment compared to published data in adults.
The strength of our study includes the cooperation of centers collecting data from all regions of the Czech Republic and timing of the survey following a peak of the critical epidemic situation in the Czech Republic with highest COVID-19 related mortality worldwide. Actual evidence of 1.67 million confirmed SARS infections as of August 2021 may assure adequately large sample for monitoring pediatric post-COVID.
The main limitations comprise differences in laboratory equipment and software between centers, and a rather short follow-up to allow for timely publishing of the results.