4 Discussion
In the current study, the length of hospital stay in most pediatric
patients with COVID-19 (average 13 days) was not significantly different
from pneumonia caused by other pathogens (average 11·2 days)17. Interestingly, the number of pediatric patients
younger than 6 months (11, 10%) was significantly less than that in
other age groups, which may be related to residual protection from
maternal immune factors. The number of patients in other two age groups
(6 Months to 6 Ys, 47, 41%; >6Ys, 56, 49%) was not
significantly different from each other. Similar to results reported in
previous studies, according to the lung involvement, the majority of
cases were mild cases and only conventional therapy for viral pneumonia
was needed12,13,18.
Severe and fatal cases in pediatric patients were very rare. Thus, early
diagnosis to avoid further spread of disease would be much more
important than treatment for individuals.
In the current study, chest CT had similar characteristic manifestations
including ground-glass opacities and consolidations with bilateral
inferior lobes, as was recently published13,19.
Of all 114 COVID-19 positive children in this study, 32 (28%) had
completely normal chest CT, 63 (55%) had no more than 2 lung lobe
lesions, and 34 patients had concurrent infections (30%). Similar to
previous studies, CT of the chest is often atypical, especially in the
early stage, resulting in difficulty in diagnosing or ruling out
COVID-19 20. In addition, in our study chest CT
identified only 53 (46%) cases by day 7 of the onset of symptoms, and
by day 14, only 76 (67%) cases of chest CT were positive. This is
totally different from the results of related research in adults. In
adults, as an important complementary tool for low-sensitive and
time-consuming RT-PCR, chest CT has first been considered as diagnostic
tool for clinical confirmed case of COVID-19 in China, where the
epidemic is most severe21,22.
Considering that the clinical manifestations and CT features of most
children are mild, CT has limited diagnostic value for children
(especially 0-7 days after onset). Therefore, CT of the chest is of
limited value in early stages of the disease, and should be discouraged
to reduce the radiation dose to children.
In the current study, throughout the entire course of COVID-19 pneumonia
in children, the diagnostic positive rate of CT has been far lower than
that of RT-PCR (All P <·05), and 28% of children have no obvious
abnormal signs of CT. However, in adults, previous studies have shown
that the positive rate of RT-PCR is only 59% to 61·3%, while the
positive rate of chest CT is 88%4,5.
These findings suggest that most infected pediatric patients have less
lung involvement in the early stages of the COVID-19 infection. As some
COVID-19 cases confirmed by RT-PCR could have no lesions on chest CT,
pathogen identification by RT-PCR have more important role in management
of infectious source. RT-PCR maybe is more reliable than CT in pediatric
patients’ diagnosis, and repeated RT-PCR is the recommended screening
for pediatric patients during the first 7 days.
In addition, the main indicator of children’s recovery is to determine
the true RT-PCR negative examination results. For well-known reasons, we
may inevitably get false negative RT-PCR results in treatment responds
evaluation. Our research shows that only RT-PCR results obtained 7 days
after the onset of symptoms are reliable. This indicates that for
children who have disappeared clinical symptoms and may totally recover,
the follow-up tests of RT-PCR to evaluate the efficacy must be performed
at least after day 7.
To reduce radiation dose of pediatric patients included in this study,
most cases (85%) had 1 or 2 chest CT scans during their hospital stay.
In our study, it was found that the median values of CT scores were low
before the 11th day from the onset of symptoms, with the median value of
1. The median value of CT score on lung involvement reached a peak at
12-17 days, with the median value of 2. After the 24th day from onset of
symptoms, the median value of CT score fell back to 1. Comparing to
median CT score of 5 on lung involvement in adults reported in previous
study 16, it
indicates that children with COVID-19 pneumonia are relatively mild. As
reported, lung involvement peaking on 6 to 11 days from symptom onset in
adults, delayed peaking in children may be related to different immune
reaction to virus 16.
In our study, CT score reached 14 in 1 case during the 0-5 days from the
onset of symptoms, which suggested that rapid progression could also be
observed in pediatric patients, even if it was rare.
There are several limitations in our study. First, even if the sample
was the largest as we known, the overall cases in the two included
hospitals was still limited. Second, as a retrospective study, selection
bias could not be avoided. Third, during this outbreak period of
COVID-19, delay in seeking care (more than 7 days from symptom onset)
would influence the diagnosis and prognosis.
In conclusion, chest CT is not recommended as a primary method for early
diagnosis in children with COVID-19, especially to avoid repeated CT
scans, while RT-PCR may have a more valuable position. For treatment
responds, reliable RT-PCR follow-up results are not available until at
least 7 days after the onset of symptoms. Only if necessary, CT can be
employed as a tool to assess lung involvement.