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Using Imaging to Supplement Testing for COVID-19

In This Article

  • Because there is still no vaccine or therapeutic drug for COVID-19, early detection and subsequent isolation of infected patients are essential to limit the spread of the disease
  • While reverse transcription polymerase chain reaction (RT-PCR) assays provide definitive diagnoses, physicians at Massachusetts General Hospital are using chest X-ray and CT to aid clinical workups in patients with suspected COVID-19
  • Imaging has become more common as a supplement for diagnosis as health care facilities have faced a shortage of testing kits for the virus

Following the emergence of the novel coronavirus (COVID-19), the use of reverse transcription polymerase chain reaction (RT-PCR) assays was established as the reference standard for definitive diagnosis of the virus. However, the shortage of testing kits in health care facilities around the world has led to the development of additional aids for diagnosis.

Radiologists at Massachusetts General Hospital Imaging have begun using chest X-ray and, selectively, computed tomography (CT) in patients with severe illness and complications like acute respiratory distress syndrome (ARDS), as a supplement to the diagnosis of COVID-19. While the Center for Disease Control and the American College of Radiology do not currently recognize chest X-ray as a substitute for RT-PCR kits in the diagnosis of the disease, the addition of imaging can aid in management of confirmed or suspected cases of COVID-19.

The Limitations of Testing Methods

While RT-PCR testing kits are still required for clinical diagnosis of COVID-19, high rates of false-negatives, long processing times and shortages of kits have disrupted efforts to contain the spread of the disease.

However, health care facilities cannot rely on chest X-ray alone. Imaging findings for COVID-19 may overlap with those for other viral infections such as influenza, yielding false-negative results for patients with suspected COVID-19. A chest CT can also appear normal in patients with confirmed COVID-19 infection.

Notably, the imaging features associated with COVID-19 have similarities to those associated with severe acute respiratory syndrome (SARS) coronavirus from the 2003 outbreak.

With added consideration of clinical history, symptoms and other laboratory tests, chest X-ray can be used to aid clinical workups in patients with suspected COVID-19.

Success in Identifying New Cases

In February 2020, researchers in the Guangdong province of China reported a substantial increase in the use of chest CT as a result of the outbreak. Additional research showed that chest CT was more sensitive than RT-PCR kits in detecting COVID-19.

In the epicenter of the outbreak—the Hubei province of China—the addition of chest CT has reportedly resulted in 14,480 confirmed new cases of COVID-19.

Structured Reporting for Chest CT Findings

The number of CT scans in patients with suspicion of the disease is on the rise, including in the U.S. At the same time, non-COVID-19 patients may have incidental findings that suggest COVID-19 pneumonia.

The Radiological Society of North America (RSNA) has therefore released a consensus statement providing guidance to radiologists in reporting CT findings that may be attributable to the disease. The statement includes standardized language to help reduce variability in reporting in cases where there is a possibility of COVID-19.

X-Ray Findings Similar to Those Seen on CT

The radiological literature pertaining to COVID-19 has mostly focused on CT. A study of patients in four Hong Kong hospitals, reported in late March, looked at the time course and severity of X-ray findings of COVID-19 and correlated them with RT-PCR results.

The study showed that abnormalities seen on chest X-ray in COVID-19 patients often mirrored those observed on CT, with bilateral lower zone consolidation that peaked 10 to 12 days after symptom onset. Also, chest X-ray findings exhibited a lower sensitivity than initial RT-PCR testing (69% versus 91%, respectively).

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