Radiological evaluation:
A total of 783 chest scans were re-evaluated with three separate
radiologists blinded to the former CT scan reports and PCR test results.
Parenchymal involvement analysis were executed via visual
semi-quantitative analysis of the three radiologists. Significant amount
of CT scans resulted in only mild (<25%) parenchymal
involvement (n=405, 84.2%). 57 patients showed 25-50% parenchymal
involvement (11.85%). Only 19 patients showed higher percentage
(>50%) of parenchymal involvement (3.95%) (Table 1).
A total of 132 CT scan were classified as “normal” whereas 170 CT
scans as “not covid”. PCR test results were positive in nearly all of
the “normal” group (n=121, 91.7%); whereas negative in most of the
“not-covid” group (n=143, 84.1%). Remaining 481 CT scans were
suspicious for COVID-19 pneumonia. PCR test results were positive in
59.2% of “typical for covid” classified scans, while negative in
70.3% of “atypical for covid” ones. Distribution of PCR test results
among results of CT scans have shown a statistically significant
difference (p<0,001). (Table 2).
Results of re-evaluation were compared with former documents related to
the CT scans. It has been found that, radiological evaluations of a
total of 145 CT scans (18.5%) have changed owing to the increased
knowledge and experience in time. After this point, these diagnostic
differences will be referred as “interpretation errors” (IE).
Retrospective evaluation was performed six months after the first phase
of the pandemic (first three months) in our country. Number of CT scans,
interpretation errors, and their monthly distribution had calculated
(Figure 2). Afterwards, results of CT scans according to the
aforementioned four classifications (normal, covid, typical for covid,
atypical for covid and not covid) were correlated with the number of
interpretation errors and PCR test results. Distribution of IEs among
results of CT scans have shown a statistically significant difference
(p<0,001). (Table 2). Furthermore, it has been found that IEs
were mostly precipitated in “not covid” group regardless of PCR
positivity (n=87, 60%). “Atypical for covid” group was found to be
the second most common one that IEs have determined (n=44, 30.34%).
Ratio of IEs in “normal” and “typical for covid” groups constitute
less than ten percent of all (9.66%). Findings were summarized at table
3.