DISCUSSION
This systematic review and meta-analysis of observational studies in
China used subgroups analyses to objectively reappraise the clinical
characteristics of patients with COVID-19-infected pneumonia, including
age, sex, chronic medical illness, symptoms, complications, chest
radiogram, etc. To our knowledge, this is the first systematic review
and meta-analysis of all available trials in China to explore the
clinical characteristics of patients with COVID-19-infected pneumonia.
Previous studies have suggested that people of all ages are susceptible
to the
COVID-19,
but older people or those with chronic medical illness are more likely
to develop severe pneumonia, ARDS, multiple organ failure, or even death
[20-22]. Congruent with previous descriptive reports, we also found
that COVID-19-infected pneumonia is common in all age groups. Moreover,
our results also revealed that people with cardiovascular disease or
endocrine system disease have a higher risk of developing ARDS, multiple
organ failure, or even death. However, there were insufficient data from
those studies to perform a further meta-analysis. Sex may also
contribute to differences in incidence of
COVID-19-infected
pneumonia. Several observational studies have reported that the
incidence of COVID-19-infected pneumonia was higher in men [6-9].
Our results were also consistent with previous report.
However,
the sex dependence of COVID-19 infections is different from that of
severe acute respiratory syndrome (SARS), which as one of the
beta-coronavirus family was more than 82% identical to RNA sequence of
COVID-19 [23-24]. But our results were limited by the sample size.
Future research may shed more light on the issue. In addition, when data
on symptoms, complications, and comorbidities were pooled, statistical
heterogeneity was detected. The source of heterogeneity may be that the
proportion of each type of symptoms, complications, and comorbidities
varied widely among the included studies.
Recent publications have reported
that the clinical characteristics of
COVID-19-infected
pneumonia mimicked those of SARS [24]. The dominant symptoms include
fever and cough. Fatigue and shortness of breath are also common
symptoms, whereas gastrointestinal symptoms were rare. Our results were
also consistent with previous report. Notably, Guan and colleagues
reported that fever occurred in only 43.8% of patients at onset of
illness and developed in 87.9% following hospitalization [10]. But
Wang and colleagues reported that the most common symptoms at onset of
illness were fever (98.6%) [9]. The above differences may confuse
readers. In combination with our results, it is considered that fever
may be the most common symptom in the course of pneumonia but not in the
onset.
Huang and colleagues reported that a few patients developed ARDS (29%),
acute cardiac injury (12%), and acute kidney injury (7%), and
suggested that the heart and kidneys are also important organs for the
COVID-19
to attack in addition to the lungs [6]. Consistent with previous
studies, our results also exhibited that COVID-19-related heart and
kidney injury were also common in severe patients.
It
seems to further suggest that the lungs may be just a channel for the
COVID-19
to attack vital organs in severe patients. But the results also need to
be further verified in future studies.
In terms of laboratory tests, the included studies-suggested that
lymphocyte absolute counts were decreased in most patients, while the
white blood cell counts were not detected to be significantly abnormal.
This result hinted that COVID-19 might also act on lymphocytes,
especially T lymphocytes, as does SARSĀCoV [25-26]. However,
impaired function of immune system may significantly increase the risk
of secondary infection in patients with
COVID-19-infected
pneumonia.
The above may also be the reason why a few patients progressed rapidly
with severe bacterial infections, which was eventually followed by
multiple organ failure.
The included studies showed that abnormalities in chest CT images were
detected among all patients on admission. The pooled results revealed
that most patients (68%) had bilateral pneumonia. The typical findings
of chest imaging showed bilateral ground glass opacity and multiple
lobular of consolidation. However, chest imaging of patients usually
changes dynamically. In clinical work, we should observe dynamically
chest imaging of patients according to their conditions. In addition, it
should not be overlooked that some
carriers
of COVID-19 may have no any clinical symptoms or exhibit typical
clinical symptoms but no abnormal changes in chest imaging [27-28].
Some limitations of this systematic review and meta-analysis should be
taken into account. First, this paper was limited to 9 observational
studies with 1,795 patients. This sample size was not large enough to
provide decisional clinical evidence. Second, some observational studies
with insufficient information were excluded, which might lead to
selection bias. Third, due to incomplete laboratory results provided by
included studies, it is not possible to further explore the relationship
between biomarkers and COVID-19-infected pneumonia.
In
summary, people of all ages are susceptible to COVID-19, but older
people or those with chronic medical illness are more likely to develop
severe pneumonia, ARDS, multiple organ failure, or even death. Moreover,
the incidence of COVID-19-infected pneumonia may be higher in men. The
dominant symptoms include fever and cough. Fatigue and shortness of
breath are also common symptoms, whereas gastrointestinal symptoms were
rare. The heart and kidneys may be also important organs for the
COVID-19 to attack in addition to the lungs. Lymphocyte absolute counts
in most patients were decreased, and that patients with secondary
bacterial infections might appear elevated leucocytes. Most patients may
have bilateral imaging abnormalities. The typical findings of chest
imaging showed bilateral ground glass opacity and multiple lobular of
consolidation.