March 1, 2020

COVID-19: Laboratory and Imaging Abnormalities

The Novel Coronavirus 2019, was first reported on in Wuhan, China in late December 2019.  The outbreak was declared a public health emergency of international concern in January 2020 and on March 11th, 2020, the outbreak was declared a global pandemic.  The spread of this virus is now global with lots of media attention.  The virus has been named SARS-CoV-2 and the disease it causes has become known as coronavirus disease 2019 (COVID-19).  This new outbreak has been producing lots of hysteria and false truths being spread, however the data surrounding the biology, epidemiology, and clinical characteristics are growing daily, making this a moving target.  This post will serve as a summary of laboratory and imaging abnormalities for COVID-19. 

To go back to the main post, click on the image below…

Laboratory Abnormalities

  • Lymphopenia (83.2%) [1]
  • Prolonged prothrombin time
  • LDH ≥250 U/L seen in 41.0% [1]
  • Procalcitionin ≥0.5 ng/mL only seen in 5.5% [1]

Imaging Abnormalities

  • Retrospective observational study determining the percentage of normal vs abnormal CXRs in patients visiting urgent care (UC) with confirmed COVID-19 [7]
    • Reviewed database of >100 UC centers in NYC and NJ
    • CXRs divided and read amongst 11 radiologists
      • All films were re-read to confirm findings
    • 636 CXRs reviewed
      • Normal CXR = 371 (58.3%)
      • Abnormal CXR = 265 (41.7%)
        • Mild Disease = 195 (30.7%)
        • Moderate Disease = 65 (10.2%)
        • Severe Disease = 5 (0.8%)
      • Predominant findings:
        • Interstitial changes = 151 (23.7%)
        • Ground glass opacities (GGOs) = 120 (18.9%)
        • Lower lobe location = 215 (33.8%)
        • Bilateral location = 133 (20.9%)
        • Multifocal = 154 (24.2%)
        • Effusions and Lymphadenopathy were uncommon
      • 1st and largest study to evaluate CXRs findings in patients with confirmed COVID-19 in UC setting
      • 468/636 (73.6%) of CXRs were initially read as normal. When asked to re-read CXR with the knowledge that the patients had COVID-19, 97 of the initial readings were changed to abnormal
      • Normal or Mildly Abnormal CXR = 566/636 (89%) despite symptoms
  • CT Chest with ground-glass infiltrates (50 – 75%) [1][4]
  • Up to 50% of patients with COVID-19 infection may have a normal CT scan 0 – 2 days after onset of flu-like symptoms from COVID-19 [4]
  • Ground-glass opacities and consolidation, with or without vascular enlargement, interlobular septal thickening, and air bronchogram sign are common CT features of COVID-19 [2]
  • Crazy paving and consolidation become the dominant CT findings , peaking around 9 – 13 days, followed by slow clearing [4]

Image Modified from Radiology 2020

Imaging DOES NOT Make the Diagnosis of a Disease it Defines the Extent of Disease and May Suggest Alternative Diagnoses

  • Correlation of Chest CT and RT-PCR Testing in Coronavirus [3]
    • RT-PCR was throat swabs
    • Positive rates of RT-PCR Assay: 59%
    • Positive rates of Chest CT: 88%
    • With a positive RT-PCR as reference, chest CT imaging sensitivity was 97%
    • Serial RT-PCR assays and CT scans: 60 to 93% of patients had initial positive chest CT consistent with COVID-19 before the initial positive RT-PCR result
    • In patients with negative RT-PCR results, 75% had positive chest CT findings (48% considered as highly likely cases and 33% as probable cases)
    • Findings suggest that if patients are only tested with RT-PCR, and the result is negative, they could be released to spread infection
  • Use of Lung US in Detection of COVID-19 PNA/ARDS [5]
    • Lung abnormalities typically develop before clinical manifestations and RT-PCR testing. Due to the high contagiousness of SARS-CoV-2 and the risk of transmission from transporting patients CT may not be the most optimal test.  Lung US gives results similar to chest CT and superior to standard CXR for evaluation of PNA/ARDS.  The added advantage is ease of use, repeatability, absence of radiation exposure, and low cost.  This is an early report of lung US on 20 patients with COVID-19 in China.  The best approach is to visualize as much of the lung as possible and not only a few zones. The findings of lung US of SARS-CoV-2 PNA/ARDS will depend on the stage of illness and the severity of lung disease. Below is a table that shows typical lung US findings in patients with COVID-19 respiratory disease in comparison with chest CT findings

Table from Springer Link 2020

    • An important limitation of lung US is that it cannot detect lesions that are deep in the lung (aerated lung blocks transmission of ultrasonography).  The abnormality must extend to the pleural surface to be visible with lung US.  Chest CT may be required to detect PNA that does not extend to the pleural surface (i.e. Chest CT should be reserved for cases where lung US is not sufficient to answer clinical questions)

Lung US Images from Springer Link 2020

Lung US Findings from Jacob Avila, MD on 5 Min Sono

Proposed Lung US Algorithm (Not Validated) by Butterfly IQ Website

    • There are some great FREE videos of COVID19 Lung US findings on the Butterfly IQ Website as well
    • Don’t forget to disinfect EVERYTHING (machine, cables, anything on the machine, and probes)
      • I use Sani-cloth wipes (grey top), which is alcohol and doesn’t have the potential to damage the US probe

COVID-19 Lung Ultrasound in Emergency Department (CLUE) [8]

  • Lung Ultrasound Scoring System (LUSS) = Anatomical Parameter
  • O2 Requirement = Physiological Parameter
  • Can help docs make disposition decision

12 Zone Lung US

COVID-19 Lung Ultrasound in ED (CLUE) Protocol

Chest CT vs Lung US of a Single Patient with COVID-19 Pneumonia (Image from Intensive Care Medicine – Link is HERE)

  • Transverse Chest CT shows multi-lobar asymmetric lung lesions with peripheral distribution of ground glass opacities, consolidation, and crazy pavement pattern
    • Lung US Images A & B: A-lines (normal aeration)
    • Lung US Images C & D: Focal confluent B lines (interstitial pattern)
    • Lung US Images E & F: Thickening and irregularity of pleural line in association with B-lines (Indicated with short yellow arrows) (Suggesting primary lung injury)

US Machine Decontamination

  • Grey top wipes to wipe everything down (remember 3 minutes between scans to be effective)
  • Take everything off the ultrasound with the exception of single use ultrasound gel and grey top wipes (Less contamination and less to wipe down after the scan)
  • For portable devices you can use ultrasound sheath over entire device, cable and phone and wipe down the sheath between scans to minimize the number of sheaths needed
  • CORE Ultrasound: COVID and Machine Decontamination
  • 5 Minute Sono: Machine Decontamination

IgM-IgG Testing [6]:

  • Currently RT-PCR, CT imaging and blood work parameters (i.e. ferritin, d-dimer, lymphopenia, etc…) are used to diagnose infection BUT…RT-PCR has some issues
  • RT-PCR limitations:
    • Long turnaround times
    • Require certified labs & expensive equipment
    • Many false negatives
  • 525 cases tested
    • 397 positive RT-PCR
    • 128 negative RT PCR
      • 352/397 tested positive = Sensitivity of 88.66%
        • 256/397 (64.48%) had both IgM and IgG Abs
      • 12/128 tested positive = Specificity of 90.63%
  • Also tested fingerstick vs peripheral blood in 10 patients
    • 7 COVID-19 positive
    • 3 Healthy volunteers
      • 3 pts IGM only
      • 4 pts IgM & IgG positive
      • All healthy volunteers negative
  • Detection of IgM and IgG combined into one test can give valuable info on time from virus exposure and provide info on virus infection time course
  • Bottom Line: Compared to RT-PCR, Rapid IgM/IgG
    • Faster (15min)
    • Simple to perform
    • No additional equipment required
    • Can be performed at the bedside or any clinic
    • Can also screen asymptomatic SARS-CoV-2 carriers

References:

  1. Guan WJ et al. Clinical Characteristics of Coronavirus Disease 2019 in China NEJM 2020. [Epub Ahead of Print]
  2. Li Y et al. Coronavirus Disease 2019 (COVID-19): Role of Chest CT in Diagnosis and Management. PMID: 32074550
  3. Ai T et al. Correlation of Chest CT and RT-PCR Testing in Coronavirus Disease 2019 (COVID-19) in China: A Report of 1014 Cases. Radiology 2020. PMID: 32101510
  4. Cheung JC et al. Staff Safety During Emergency Airway Management for COVID-19 in Hong Kong. Lancet Respir Med 2020. PMID: 32105633
  5. Peng QY et al. Findings of Lung Ultrasonography of Novel Corona Virus Pneumonia During the 2019 – 2020 Epidemic. Springer Link 2020. [Epub Ahead of Print]
  6. Li Z et al. Development and Clinical Application of a Rapid IgM-IgG Combined Antibody Test for SARS-CoV-2 Infection Diagnosis. J Med Virol 2020. PMID: 32104917
  7. Weinstock MB et al. Chest X-Ray Findings in 636 Ambulatory Patients with COVID-19 Presenting to an Urgent Care Center: A Normal Chest X-Ray is no Guarantee. JUCM 2020. [Epub Ahead of Print]
  8. Manivel V et al. CLUE: COVID-19 Lung Ultrasound in Emergency Department. Emergency Med Australas 2020. PMID: 32386264

For More Thoughts on This Topic Checkout:

Post Peer Reviewed By: Anand Swaminathan, MD (Twitter: @EMSwami) and Mizuho Morrison, DO (Twitter: mizuhomorrison)

Cite this article as: Salim Rezaie, "COVID-19: Laboratory and Imaging Abnormalities", REBEL EM blog, March 1, 2020. Available at: https://rebelem.com/covid-19-laboratory-and-imaging-abnormalities/.
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Salim Rezaie

Emergency Physician at Greater San Antonio Emergency Physicians (GSEP)
Creator & Founder of REBEL EM
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