DISCUSSION:
In our study, we aimed to expose the radiologists’ increasing experience
on evaluation of chest-CT findings of COVID-19 pneumonia. We have
focused on some unobserved challenges on radiologists’ in the COVID-19
pandemic to better understand the diagnostic differences in
re-evaluation.
Correlation of re-evaluated chest CT results with PCR tests have
demonstrated that PCR test was negative in 84.1% of the scans in “not
covid” group. On the other hand, the 91.7% PCR-positivity were
calculated in the cases labelled for “normal”. This finding can be
explained with the vigorous use of CT in the ER setting, even for the
patients who has COVID-19 infection but lack of pneumonia. Calculations
with “typical for covid”, “atypical for covid” and combination of
this two groups have resulted in 62.8% sensitivity and 40% specificity
of Chest-CT according to PCR test results.
We have identified diagnostic differences in 18.5% of the chest CT
scans in our cohort. The distribution of this EIs have shown a dramatic
accumulation within the first 60 days of pandemic in our country. After
this point, the of IEs decrease down to 11.18% (figure 2). There are
some reasons that can explain the possible causes of this relatively
high EI ratios and its course among the first three months of pandemic.
First of all, both national and global total number of cases and new
confirmed cases prominently increased within the first two months. The
number of total cases significantly increase from
~116.000 to ~3.2 million with an
increase in new confirmed case from 4600 to 86.000/day worldwide.
Similarly, a total of ~120.000 cases have been
identified in our country between 10th March and 1stMay, 2020 with a 2615/day new confirmed cases on 1stMay (5). Our institution as well as most of the healthcare centres
worldwide have faced striking hospital admission rates up to
~1000/day with the spread of coronavirus. Between
1st of May and 1st of June, new
confirmed daily cases decrease by 67.92%. As of 8thof January 2021, the cumulative number of covid cases are nearly 1.5
million in our country (5). We have re-evaluated the study cohort with a
remarkable experience of ~17.000 chest CT scans reported
in the past 9 months at our institution.
During pandemic, workload of radiologists have expeditiously increased
parallel to the admissions with the suspicion of COVID-19. According to
the COVID-19 guidelines published by the ministry of health
(appendix-2), chest CT scanning have become the secondary diagnostic
tool after the gold standard PCR testing. To overcome the delay in
diagnosis due to the PCR testing, clinicians encouraged to use the CT
scan as the quickest way to isolate/hospitalize the COVID-19 infected
patients (7). Moreover, Chest-CT gained an important role in
clarification of PCR-false negative but clinically highly suspected
cases.(8) These all have seem to be contributed to acquisition of 5721
Chest CT-scans within this three month period. For comparison, there
were approximately 900 chest CTs performed at out institution between
the same months of the last year (March to June, 2019). Radiologists on
shifts were directly affected from this six-fold increase; up to a total
of 140 covid-suspected chest CT scans were reported in a day, along with
the other non-covid emergencies. Reporting time was approximately 10-30
minutes after the acquisition. Another difficulty was that the covid
dedicated CT scanning protocol included approximately 320 axial slices
with a 1 mm slice thickness which makes it more time consuming than the
standard chest CT scanning protocol with 3-5 mm slice thickness. All in
all, exponentially increased admission rates along with the increased
number of covid dedicated, thin slice chest CT scans have become grounds
for possible interpretation errors.
Another point worth mentioning is that; although most typical signs of
covid pneumonia on chest CT had first identified in Wuhan-China,
numerous atypical signs had evolved with the spread of the infection to
different profile of patients. As Falaschi et al . stated,
incorporation of China experience along with the other previously
contaminated countries into daily clinical practice seems to have caused
an improvement in our diagnostic accuracy (4). The recognition of the
relationship between atypical findings for COVID-19 pneumonia on Chest
CT may have contributed to the decline of IE rate. Another possible
contributor is the aggregation of educational activities focused on
radiological findings of covid pneumonia in the first two months.
Further analysis have shown a marked uneven distribution of IEs among
the four CT result groups. More than half of the errors have been made
in the “not covid”, followed by the “atypical for covid” group. IEs
in the re-evaluated “not covid” group were mostly consisted of
incorrect diagnosis for “atypical for covid”. Similarly, analysis of
re-evaluated “atypical covid” group have shown a marked incorrect
diagnosis for “typical for covid”. These findings have shown us that
that the radiological hallmarks of covid pneumonia were successfully
identified but there were lack of experience and knowledge, specifically
about atypical radiological findings. This situation had probably
created a tendency to not to exclude the covid diagnosis, yet point out
a suspicion with the statement of “atypical for covid” in CT reports.
Another issue to mention is that, there are subspecialized academic and
staff radiologists at our department. The COVID-19 pandemic have
necessitated rapid responses from radiology departments to overcome the
increased demand on diagnosis and management of covid pneumonia. Along
with the partial cancellation of elective diagnostic/interventional
procedures and outpatient diagnostic services; nearly all radiologists
were integrated into a team dedicated to COVID-19 diagnosis. Therefore,
as Vijayasarathi et al . stated, subspecialised radiologists have
faced an unexpected challenge in this crisis to maintain their
versatility in reporting chest CT scans (9). Similarly, Shi et
al. and Cavallo et al. have also mentioned imperative
outside-role definition of radiology employees (10,11). Hereby, this
situation might also contribute to the escalation of interpretation
errors. Considering together with the increased workload and physical
and psychological stress of pandemic, it seems nearly inevitable to make
interpretation errors in the COVID-19 outbreak.
There are some limitations this study. First, we could have included
only 13.6% of the Chest CT scans due to lack or delay of PCR test
results. Second, we have ignored decline in non-COVID CT cases per/day
and focused on COVID dedicated CT reporting volume.
There’s no doubt that COVID pandemic made a huge impact on radiology
practices worldwide. Increment of covid-related admission rates and
relevant increase in daily workload, rotations of subspecialized
personnel for urgent health care management along with growing
diagnostic experience over time have possible effects on radiology
departments’ performance.