Diagnosis and Journey

Topic Progress:

Pearls for the Diagnosis and Journey

1. The COVID-19 PCR swab is the most widely used method to diagnose COVID-19, though you may need multiple swabs to confirm the diagnosis.
2. The vast majority of patients have mild illness and do not need hospital care.
3. The patients in hospital are at high risk for clinical deterioration and death.

The Swab

Click here to read the best practice for collecting a nasopharyngeal swab.

Samples are collected by swabbing the upper airway and swabs are analyzed for viral load, RT-PCR has excellent specificity however sensitivity has been reported to be as low as 60-70% (for example if a test is positive you can have a high degree of certainty that the patient has SARS-COV2, however multiple negative tests may be required to reliably exclude the disease)1. RT-PCR also requires specialised laboratory equipment and has long turn around times.

CT Scan, X-Ray and Ultrasound

In combination with clinical correlation, CT scan can diagnose parenchymal lung disease that is likely of COVID etiology, but it cannot speak to causative organisms; however, CT scan can be one method to track disease progression1. A limitation of CT is that there may be 1-2 days where a patient is symptomatic but has no discernable radiological signs.2-3

A chest x-ray is faster and easier to obtain than a CT. It also removes the need to disinfect an entire CT scanner post imaging; however, a CXR is less likely to detect certain lung disease than a CT.4

There have been reports that lung ultrasonography may have a role in the assessment of the patient with suspected COVID-19 due to its low-cost and relative portability. Initial data on its use has been published including a claim that it may have superior sensitivity for detecting lung disease than chest x-ray.5-6

Point of Care Blood Tests

Point of care blood tests for antibodies (IgM/IgG tests) are cheaper and faster than PCR (can return a result in around 15 minutes) and initial data looked promising7; however a recent paper from Italy showed disappointing sensitivity when comparing these tests with RT-PCR results.8 These assays will need additional validation prior to their widespread adoption (for example the Australian Therapeutic Goods Administration has authorized these tests under the provision that further data is made available within the next 12 months).9-10

Journey




One Theory of Disease Progression11
  • Stage 1: Patients with mild symptoms similar to a common cold or seasonal influenza.
  • Stage 2: Patients experience the same symptoms of stage one however there is now an inflammatory component to the disease leading to the development of pneumonia, this causes some shortness of breath.
  • Stage 3: Patients experience a widespread, multi-organ, cytokine-mediated systemic inflammatory response, referred to in the literature as a cytokine storm.12

Patients in stage 1 or 2 will likely manage at home or on a ward with patients in stage 3 likely requiring ICU admission.

Patients who will develop respiratory failure and require ICU admission will likely do so after day 7 of symptoms. Respiratory failure is a common indication for ICU admission. Renal failure or shock may also precipitate the need for critical care, particularly in those presenting with silent hypoxemia18. Should patients deteriorate and require ICU care they are likely to develop acute respiratory distress syndrome; potentially withshock, cardiac injury, dysrhythmias, acute kidney injury, rhabdomyolysis, liver injury and disseminated intravascular coagulation.13-15

Multi-organ failure is often an extremely late development and common patient screening tools (NEWS, qSOFA) are unlikely to preemptively identify those patients who will become unwell14. There has been some conjecture that COVID-19 may infiltrate myocardial tissue leading to viral myocarditis16; however, these diagnoses have been based on clinical criteria and elevated high-sensitivity troponin. Given that a formal diagnosis of myocarditis requires a tissue biopsy, and at time of writing, the results of no such biopsy could be found in the literature, the precise etiology of the myocardial injury remains unclear.17

References

1. Fang, Y., Zhang, H., Xie, J., Lin, M., Ying, L., Pang, P., & Ji, W. (2020). Sensitivity of Chest CT for COVID-19: Comparison to RT-PCR. Radiology, 200432. doi: 10.1148/radiol.2020200432

2. Rodrigues, J., Hare, S., Edey, A., Devaraj, A., Jacob, J., & Johnstone, A. et al. (2020). An update on COVID-19 for the radiologist – A British society of Thoracic Imaging statement. Clinical Radiology. doi: 10.1016/j.crad.2020.03.003

3. Kanne, J., Little, B., Chung, J., Elicker, B., & Ketai, L. (2020). Essentials for Radiologists on COVID-19: An Update – Radiology Scientific Expert Panel. Radiology, 200527. doi: 10.1148/radiol.2020200527

4. Ng, M., Lee, E., Yang, J., Yang, F., Li, X., & Wang, H. et al. (2020). Imaging Profile of the COVID-19 Infection: Radiologic Findings and Literature Review. Radiology: Cardiothoracic Imaging, 2(1), e200034. doi: 10.1148/ryct.2020200034

5. Peng, Q., Wang, X., Zhang, L., & Chinese Critical Care Ultrasound Study Group (CCUSG). (2020). Findings of lung ultrasonography of novel corona virus pneumonia during the 2019–2020 epidemic. Intensive Care Medicine. doi: 10.1007/s00134-020-05996-6

6. Huang, Y., Wang, S., Liu, Y., Zhang, Y., Zheng, C., & Zheng, Y. et al. (2020). A Preliminary Study on the Ultrasonic Manifestations of Peripulmonary Lesions of Non-Critical Novel Coronavirus Pneumonia (COVID-19). SSRN Electronic Journal. doi: 10.2139/ssrn.3544750

7. Li, Z., Yi, Y., Luo, X., Xiong, N., Liu, Y., & Li, S. et al. (2020). Development and Clinical Application of A Rapid IgM‐IgG Combined Antibody Test for SARS‐CoV‐2 Infection Diagnosis. Journal Of Medical Virology. doi: 10.1002/jmv.25727

8. Cassaniti, I., Novazzi, F., Giardina, F., Salivaro, F., Sachs, M., & Perlini, S. et al. (2020). Performance of VivaDiagTM COVID-19 IgM/IgG Rapid Test is inadequate for diagnosis of COVID-19 in acute patients referring to emergency room department. Journal Of Medical Virology. doi: 10.1002/jmv.25800

9. Therapeutic Goods Administration (TGA). (2020). COVID-19 diagnostic tests included on the ARTG for legal supply in Australia. Retrieved 29 March 2020, from https://www.tga.gov.au/covid-19-diagnostic-tests-included-artg-legal-supply-australia

10. Public Health Laboratory Network (PHLN). (2020). PHLN statement on emergency testing provisions for SARS-CoV-2 (the virus that causes COVID-19). Retrieved 29 March 2020, from https://www.health.gov.au/resources/publications/phln-statement-on-emergency-testing-provisions-for-sars-cov-2-the-virus-that-causes-covid-19

11. Siddiqi, H., & Mehra, M. (2020). COVID-19 Illness in Native and Immunosuppressed States: A Clinical-Therapeutic Staging Proposal. The Journal Of Heart And Lung Transplantation. doi: 10.1016/j.healun.2020.03.012

12. Mehta, P., McAuley, D., Brown, M., Sanchez, E., Tattersall, R., & Manson, J. (2020). COVID-19: consider cytokine storm syndromes and immunosuppression. The Lancet, 395(10229), 1033-1034. doi: 10.1016/s0140-6736(20)30628-0

13. Wang, D., Hu, B., Hu, C., Zhu, F., Liu, X., & Zhang, J. et al. (2020). Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus–Infected Pneumonia in Wuhan, China. JAMA, 323(11), 1061. doi: 10.1001/jama.2020.1585

14. Guan, W., Ni, Z., Hu, Y., Liang, W., Ou, C., & He, J. et al. (2020). Clinical Characteristics of Coronavirus Disease 2019 in China. New England Journal Of Medicine. doi: 10.1056/nejmoa2002032

15. Meng, L., Qiu, H., Wan, L., Ai, Y., Xue, Z., & Guo, Q. et al. (2020). Intubation and Ventilation amid the COVID-19 Outbreak. Anesthesiology, 1. doi: 10.1097/aln.0000000000003296

16. Ruan, Q., Yang, K., Wang, W., Jiang, L., & Song, J. (2020). Clinical predictors of mortality due to COVID-19 based on an analysis of data of 150 patients from Wuhan, China. Intensive Care Medicine. doi: 10.1007/s00134-020-05991-x 17.

17. Caforio, A., & Casadei, B. (2020). Cardiac complications in COVID-19: myocarditis. Retrieved 28 March 2020, from https://www.youtube.com/embed/3qINtzH2PfI?rel=0&autoplay=1

18. Xie, J., Tong, Z., Guan, X. et al. Critical care crisis and some recommendations during the COVID-19 epidemic in China. Intensive Care Med (2020). https://doi.org/10.1007/s00134-020-05979-7

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