Summary
In a series of 51 patients with chest CT and RT-PCR assay performed within 3 days,
the sensitivity of CT for COVID-19 infection was 98% compared to RT-PCR sensitivity
of 71% (p<.001).
Introduction
In December 2019, an outbreak of unexplained pneumonia in Wuhan [1] was caused by
a new coronavirus infection named COVID-19 (Corona Virus Disease 2019). Noncontrast
chest CT may be considered for early diagnosis of viral disease, although viral nucleic
acid detection using real-time polymerase chain reaction (RT-PCR) remains the standard
of reference. Chung et al. reported that chest CT may be negative for viral pneumonia
of COVID-19 [2] at initial presentation (3/21 patients). Recently, Xie reported 5/167
(3%) patients who had negative RT-PCR for COVID-19 at initial presentation despite
chest CT findings typical of viral pneumonia [3]. The purpose of this study was to
compare the sensitivity of chest CT and viral nucleic acid assay at initial patient
presentation.
Materials and Methods
The retrospective analysis was approved by institutional review board and patient
consent was waived. Patients at Taizhou Enze Medical Center (Group) Enze Hospital
were evaluated from January 19, 2020 to February 4, 2020. During this period, chest
CT and RT-PCR (Shanghai ZJ Bio-Tech Co, Ltd, Shanghai, China) was performed for consecutive
patients who presented with a history of 1) travel or residential history in Wuhan
or local endemic areas or contact with individuals with individuals with fever or
respiratory symptoms from these areas within 14 days and 2) had fever or acute respiratory
symptoms of unknown cause. In the case of an initial negative RT-PCR test, repeat
testing was performed at intervals of 1 day or more. Of these patients, we included
all patients who had both noncontrast chest CT scan (slice thickness, 5mm) and RT-PCR
testing within an interval of 3 days or less and who had an eventual confirmed diagnosis
of COVID-19 infection by RT-PCR testing (Figure 1). Typical and atypical chest CT
findings were recorded according to CT features previously described for COVD-19 (4,5).
The detection rate of COVID-19 infection based on the initial chest CT and RT-PCR
was compared. Statistical analysis was performed using McNemar Chi-squared test with
significance at the p <.05 level.
Figure 1:
Flowchart for patient inclusion.
Results
51 patients (29 men and 22 women) were included with median age of 45 (interquartile
range, 39- 55) years. All patients had throat swab (45 patients) or sputum samples
(6 patients) followed by one or more RT-PCR assays. The average time from initial
disease onset to CT was 3 +/- 3 days; the average time from initial disease onset
to RT-PCR testing was 3 +/- 3 days. 36/51 patients had initial positive RT-PCR for
COVID-19. 12/51 patients had COVID-19 confirmed by two RT-PCR nucleic acid tests (1
to 2 days), 2 patients by three tests (2-5 days) and 1 patient by four tests (7 days)
after initial onset.
50/51 (98%) patients had evidence of abnormal CT compatible with viral pneumonia at
baseline while one patient had a normal CT. Of 50 patients with abnormal CT, 36 (72%)
had typical CT manifestations (e.g. peripheral, subpleural ground glass opacities,
often in the lower lobes (Figure 2) and 14 (28%) had atypical CT manifestations (Figure
3) [2]. In this patient sample, difference in detection rate for initial CT (50/51
[98%, 95% CI 90-100%]) patients was greater than first RT-PCR (36/51 [71%, 95%CI 56-83%])
patients (p<.001).
Figure 2a:
Examples of typical chest CT findings compatible with COVID-19 pneumonia in patients
with epidemiological and clinical presentation suspicious for COVID-19 infection.
A, male, 74 years old with fever and cough for 5 days. Axial chest CT shows bilateral
subpleural ground glass opacities (GGO). B, female, 55 years old, with fever and cough
for 7 days. Axial chest CT shows extensive bilateral ground glass opacities and consolidation;
C, male, 43 years old, presenting with fever and cough for 1 week. Axial chest CT
shows small bilateral areas of peripheral GGO with minimal consolidation; D, female,
43 years old presenting with fever with cough for 5 days. Axial chest CT shows a right
lung region of peripheral consolidation.
Figure 2b:
Examples of typical chest CT findings compatible with COVID-19 pneumonia in patients
with epidemiological and clinical presentation suspicious for COVID-19 infection.
A, male, 74 years old with fever and cough for 5 days. Axial chest CT shows bilateral
subpleural ground glass opacities (GGO). B, female, 55 years old, with fever and cough
for 7 days. Axial chest CT shows extensive bilateral ground glass opacities and consolidation;
C, male, 43 years old, presenting with fever and cough for 1 week. Axial chest CT
shows small bilateral areas of peripheral GGO with minimal consolidation; D, female,
43 years old presenting with fever with cough for 5 days. Axial chest CT shows a right
lung region of peripheral consolidation.
Figure 2c:
Examples of typical chest CT findings compatible with COVID-19 pneumonia in patients
with epidemiological and clinical presentation suspicious for COVID-19 infection.
A, male, 74 years old with fever and cough for 5 days. Axial chest CT shows bilateral
subpleural ground glass opacities (GGO). B, female, 55 years old, with fever and cough
for 7 days. Axial chest CT shows extensive bilateral ground glass opacities and consolidation;
C, male, 43 years old, presenting with fever and cough for 1 week. Axial chest CT
shows small bilateral areas of peripheral GGO with minimal consolidation; D, female,
43 years old presenting with fever with cough for 5 days. Axial chest CT shows a right
lung region of peripheral consolidation.
Figure 2d:
Examples of typical chest CT findings compatible with COVID-19 pneumonia in patients
with epidemiological and clinical presentation suspicious for COVID-19 infection.
A, male, 74 years old with fever and cough for 5 days. Axial chest CT shows bilateral
subpleural ground glass opacities (GGO). B, female, 55 years old, with fever and cough
for 7 days. Axial chest CT shows extensive bilateral ground glass opacities and consolidation;
C, male, 43 years old, presenting with fever and cough for 1 week. Axial chest CT
shows small bilateral areas of peripheral GGO with minimal consolidation; D, female,
43 years old presenting with fever with cough for 5 days. Axial chest CT shows a right
lung region of peripheral consolidation.
Figure 3a:
Examples of chest CT findings less commonly reported in COVID-19 infection (atypical)
in patients with epidemiological and clinical presentation suspicious for COVID-19
infection. A, male, 36 years old with cough for 3 days. Axial chest CT shows a small
focal and central ground glass opacity (GGO) in the right upper lobe; B, female, 40
years old. Axial chest CT shows small peripheral linear opacities bilaterally. C,
male, 38 years old. Axial chest CT shows a GGO in the central left lower lobe; D,
male, 31 years old with fever for 1 day. Axial chest CT shows a linear opacity in
the left lower lateral mid lung.
Figure 3b:
Examples of chest CT findings less commonly reported in COVID-19 infection (atypical)
in patients with epidemiological and clinical presentation suspicious for COVID-19
infection. A, male, 36 years old with cough for 3 days. Axial chest CT shows a small
focal and central ground glass opacity (GGO) in the right upper lobe; B, female, 40
years old. Axial chest CT shows small peripheral linear opacities bilaterally. C,
male, 38 years old. Axial chest CT shows a GGO in the central left lower lobe; D,
male, 31 years old with fever for 1 day. Axial chest CT shows a linear opacity in
the left lower lateral mid lung.
Figure 3c:
Examples of chest CT findings less commonly reported in COVID-19 infection (atypical)
in patients with epidemiological and clinical presentation suspicious for COVID-19
infection. A, male, 36 years old with cough for 3 days. Axial chest CT shows a small
focal and central ground glass opacity (GGO) in the right upper lobe; B, female, 40
years old. Axial chest CT shows small peripheral linear opacities bilaterally. C,
male, 38 years old. Axial chest CT shows a GGO in the central left lower lobe; D,
male, 31 years old with fever for 1 day. Axial chest CT shows a linear opacity in
the left lower lateral mid lung.
Figure 3d:
Examples of chest CT findings less commonly reported in COVID-19 infection (atypical)
in patients with epidemiological and clinical presentation suspicious for COVID-19
infection. A, male, 36 years old with cough for 3 days. Axial chest CT shows a small
focal and central ground glass opacity (GGO) in the right upper lobe; B, female, 40
years old. Axial chest CT shows small peripheral linear opacities bilaterally. C,
male, 38 years old. Axial chest CT shows a GGO in the central left lower lobe; D,
male, 31 years old with fever for 1 day. Axial chest CT shows a linear opacity in
the left lower lateral mid lung.
Discussion
In our series, the sensitivity of chest CT was greater than that of RT-PCR (98% vs
71%, respectively, p<.001). The reasons for the low efficiency of viral nucleic acid
detection may include: 1) immature development of nucleic acid detection technology;
2) variation in detection rate from different manufacturers; 3) low patient viral
load; or 4) improper clinical sampling. The reasons for the relatively lower RT-PCR
detection rate in our sample compared to a prior report are unknown (3). Our results
support the use of chest CT for screening for COVD-19 for patients with clinical and
epidemiologic features compatible with COVID-19 infection particularly when RT-PCR
testing is negative.