Efficacy of Chest CT for COVID-19 Pneumonia in France

Key Results

• In a national survey of 26 hospitals (N= 4824 subjects), chest CT sensitivity and specificity for diagnosing COVID-19 pneumonia were 90% and 91%, respectively.

• In 103 patients with an initial positive chest CT finding(s) for COVID-19 and a negative initial RT-PCR test, a repeat RT-PCR was positive in 90% (93/103).

• In patients with both negative chest CT and RT-PCR, the negative predictive value regarding final discharge diagnosis for COVID-19 was 99% (2035/2050 patients).

CT TESTING FOR COVID: BENEFITS EXCEED RISKS

We estimate the benefits from the use of CT scans in conjunction with RT-PCR for diagnosis of COVID- 19 in symptomatic individuals. Our calculation shows that for 10,000 CT-scans 124 lives are saved this year (within months), 2,074 diagnosed cases are prevented, 415 hospitalizations are prevented along with subsequent short and long term disability. Well established estimates imply 1 future cancer may result.

COMBINING PCR AND CT TESTING FOR COVID

We analyze the effect of using a screening CT-scan for evaluation of potential COVID-19 infections in order to isolate and perform contact tracing based upon a viral pneumonia diagnosis. RT-PCR is then used for continued isolation based upon a COVID diagnosis. Both the low false negative rates and rapid results of CT-scans lead to dramatically reduced transmission. The reduction in cases after 60 days with widespread use of CT-scan screening compared to PCR by itself is as high as 50x, and the reduction of effective reproduction rate R(t) is 0:20. Our results imply that much more rapid extinction of COVID is possible by combining social distancing with CT-scans and contact tracing.

TESTING TREATMENTS FOR COVID-19: CT-SCANS FOR VISIBLE DISEASE PROGRESSION

What we can do immediately is to help improve physicians ability to see what is happening. One of the best tools for this is CT-scans? They provide a 3-D view of what is going on in the lungs, including both the number of sites of damage and their extent. They can show the infection even before the patient reports symptoms (presymptomatic) and or when they are mild. This gives a snapshot of the condition of the lung early in the disease, or as it progresses.

BREAKING THE TESTING LOGJAM: CT SCAN DIAGNOSIS

One way to break free from this deadlock is the assistance from CT imaging. COVID-19 patients have characteristic features, like multifocal patchy shadows or ground-glass opacities, in chest image even for asymptomatic cases. CT scanners are an existing resource in medical systems, and CT results can be obtained within 15 minutes. The use of CT for pre-screen of diagnosis, can expand testing capacity dramatically.