Introduction:
At the end of 2019, a novel coronavirus was identified as the cause of a
cluster of pneumonia cases in Wuhan, a city in the Hubei Province of
China. It rapidly spread, resulting in an epidemic throughout China,
followed by an increasing number of cases in other countries throughout
the world. (1). Following the detection and announcement of the first
cases of COVID-19 on February 20, the infection rate and death toll from
the disease has been on the rise (2). The responsible causative agent,
namely SARS-CoV-2, is an enveloped RNA virus of Coronaviridae family.
The transmission of COVID19 occurs via respiratory droplets or
contaminated surfaces (3). The symptoms of COVID-19 are non-specific,
which range from asymptomatic to severe pneumonia and can lead to death
(4). The majority of patients present with mild respiratory tract
infection, mostly commonly fever (82%) and cough (81%). Severe
pneumonia and acute respiratory distress syndrome (ARDS) have been
reported in 14% of cases with overall mortality rate of 2% (5).
Nevertheless, these figures are rising concomitant with the expansion of
pandemic depending on the country involved (6). SARS-CoV infection in
humans leads to an acute respiratory illness varying from mild febrile
disease to ALI and in some cases ARDS and death (7, 8). Considering the
high infectivity of COVID-19, rapid and precise diagnostic methods are
urgently required to detect, isolate and treat the patients as soon as
possible, which might decrease mortality rates and the risk of community
contamination (9). Computed tomographic (CT) imaging is extensively
applied for the early diagnosis of COVID-19, but chest CT may not
distinguish this disease from other viral pneumonias (10, 11). Nucleic
acid assay, gene sequencing, and serology tests (IgM and IgG) from
throat swabs or blood samples have been developed to confirm the
diagnosis of COVID-19 (12). However, clinicians from Wuhan have
addressed the issue of high false negative rates of PCR or antibody
detection (13). However, rRT-PCR results often require 5 to 6 hours to
be prepared, while CT results can be obtained much faster (9). Chunqin
Long et al. revealed that the sensitivity of CT examination was 97.2%
at presentation, whereas the sensitivity of first round rRT-PCR was
84.6% (9). This difference may be a function of sample collection
because pharyngeal and nasal sampling are more straightforward
collection methods, while lower respiratory tract sampling is relatively
difficult to perform and bears the risk of infection for susceptible
medical staff (14). The sensitivity of rRT-PCR kit can also give rise to
false negative results (9).
Simultaneous use of medical history, clinical manifestations, chest CT,
and viral test has been found to present high sensitivity (92–97%)
(15, 16).
A major challenge for the restriction of SARS-CoV-2 spread is that
pre-symptomatic people are infectious for others (17). Recent reports
indicated that patients can be infectious 1-3 days before the onset of
symptoms and that up to 40-50% of cases may be attributable to
transmission from asymptomatic or presymptomatic individuals (18, 19).
Patients have high nasopharyngeal loads of virus just before or soon
after the onset of symptoms , which subsequently fall over the course of
approximately one week (20). Patients with severe disease can release
the virus for longer periods, although the shedding duration of
infectious virus is not precisely known (21). Evaluation and management
of COVID-19 is determined by the severity of the illness. According to
initial data taken from China, 81% of people with COVID-19 had mild or
moderate disease (including people without pneumonia and those with mild
pneumonia), 14% had severe disease, and 5% showed critical illness
(22).
According to the guidelines of World Health Organization (WHO), the risk
of COVID-19 virus infection is not ruled out if one or more negative PCR
tests are observed. Factors such as low sample quality (lack of
sufficient DNA in the sample), inappropriate time of sampling (delayed
or early sampling), improper storage and transportation of the sample,
and inherent technical reasons for testing including virus mutations or
PCR inhibitions (such as improper swap use, etc.,) can affect PCR
testing and lead to false negative responses (23).
Due to the rapid spread of COVID19 disease in Iran, increasing number of
patients in a short period of time, lack of cooperation of some patients
in the sampling process, limited access to RT-PCR testing, assuming PCR
as a time consuming test and inability to repeat negative tests, many
suspected patients with COVID19 were hospitalized in medical centers
based on clinical symptoms, vital signs, laboratory data and CT-Scan
findings.
Due to limitation of available hospital beds, some of the hospitalized
patients showing minor clinical symptoms, mild CT-Scan changes and
improved vital signs who had negative PCR results were discharged by
physician’s clinical judgement within a few days of admission. There
were several reports of exacerbated symptoms and re-hospitalization of
patients in severe conditions .Meanwhile, the positive or negative PCR
results have at times led the physicians into misinterpretation of
patient’s clinical conditions. The decision to continue treatment or
discharge the patient from the hospital in those with mild clinical
symptoms, negative PCR test and positive CT is an important question for
physicians.
Accordingly, the goal of this study is to investigate the importance of
clinical symptoms, initial vital signs, laboratory findings and chest
CT-Scan findings among patients with negative and positive PCR results.