chest imaging in covid-19
TRANSCRIPT
Chest imaging in COVID-19
Iain Au-Yong, Consultant Radiologist.
Objectives
Background –first wave
• Reflections from first wave
• Very little known prior to first wave, preliminary data from China (CT)
• Suggested that imaging could be used for diagnosis and triage
• CXR preferred in Italy.
• Reference:
• Ai T, Yang Z, Hou H, 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 Feb 26:200642
Diagnosis of COVID-19
• Principles:
• RT-PCR is the gold standard for diagnosis but can be false negative (2-29%)
• Not readily available during the first wave
• Role of imaging:
• Diagnosis, for triage and management
• CXR and CT are the main imaging modalities in use, US is not in widespread use.
• Chest imaging has limited sensitivity and specificity.
• It should therefore be used in conjunction with clinical suspicion and biochemical indices (such as lymphopenia)
• Prognostication
• Detection and management of complications (egthrombosis)
Technical considerations
CT
• Less availability
• Disinfection more complex, risks to staff
• Additional burden of radiation dose and contrast administration (AKI in COVID),
• More sensitive. Specificity an issue
• Complex interpretation.
• Alternative diagnoses more readily made (PE, heart failure)
CXR
• More availability
• Portable CXR more practical, disinfection more straightforward
• Less sensitive. Specificity an issue
• Interpretation more straightforward.
• Can provide prognostic information
Covid 19 NUHT Triage v 217.3.20Suspected Diagnosis of Covid based on symptoms
Dry cough, Fatigue, Myalgia, Fever, Dyspnoea
For Escalation?Based on premorbid function and comorbidities*
Discuss with Respiratory Service
CT Chest*
CT featuresPeripheral multifocal airspace opacities
-Ground glass shadowing-Consolidation
(Majority will have bilateral involvement)
ClearOr Pleural effusion/Pneumothorax
No
F22/QMC
Well- Home
Unwell- ED
QMC/Gen MedConsider second
swab
NCH/Resp/Covid ward
1st Viral PCR
*Escalation factors need definingEg not for escalation-Chronic lung diseaseChronic heart disease
Age criteria
Yes
+ve -ve
NCH/Resp/Covid ward
QMCEDCOVID-19ADULTFLOWPROCESS–2ndApril**SeeEDIU&inpatientpathwayoptionsbelowforfulldetailsofadmissionpathways
1. Anynewcoughinlast7days
OR2. Newfeverwithin7days
OR3. Ambulancetemperature>
37.7C?
Areanyofthefollowingpresent?
• Sneezing,Nasaldischargeorcongestion
• Hoarsenessorsorethroat
• Dyspnoea/SOBorwheezing
• Fatigue/Myalgia
• Delerium/sepsisunknownsource
• D&V–(HCOPpatients)
Immediatedischargepossible?1. Patientlookswell2. HR<1003. O2Sats>94%(Roomair)
(>88%inCOPD)4. Norespiratorydistress
GiveinformationleafletProvidedischargeadviceRecordObs&decisiononMEDWAY
NON-COVIDProcess“ResusinMAJORS”
(MU1-10)MT–MU1
PaedsMT–MU5MUPatients–MU11-20
Illness-GREEN
DoespatientneedHighDependencyCOVID?(RESUS)
• NEWS>8
• Sats<92%despiteHFO2orrespdistress
• Potentialfordeterioration
DotheyneedanAGP?• CardiacArrest
Adult-(MACU1)Paeds–(Paedstreatmentroom)
• IntubationnorCPAP/NIV
A–Transfertheatre/AICUifpossibleB-UTUBay11C-MACUbay1+9D–COVIDResuslastoptionorimminentarrest
TransfertoCOVIDwardNCH&callnursing
stafftohandover
TransferEDIU1or2(MACU/UTU)
completeCXR&swabASAP
POTENTIALCOVID-19
Canbede-escalatedasNON-COVID??
CXR?COVID
Safefordischargeatanystage
AdmitNon-
COVIDwardQMC
Consider
HCOPPathwayorPalliativecare
SpecialistcareneededatQMCsite?
(Surgery,MT,complexgastroetc.)
AdmitunderspecialityatQMC
insideroom
Home
Home
Aretheyforescalation?
NO
NO
YES
YES
YES
YES
YES
YES
YES
AdmitNon-COVIDward
QMC
YES
NO
NO
YES
NO
Likelyclinicalsyndrome,withlymphopenia&raisedCRP?
NO
NO
RingRespBATONphone
COVIDCTPA
NO YESNO
NEGATIVE POSITIVE
ACCEPTED
NOTACCEPTED
NO
CXR
• Sensitivity 56% specificity 60%. (London, April 2020)
• (Borakati et al)
• However these figures vary with prevalence.
• Hot reporting
• Vvvv. Incidental COVID.
Borakati et al, BMJ Open. 2020 Nov 6;10(11):e042946.
Diagnostic accuracy of X-ray versus CT in COVID-19: a propensity-matched database study
BSTI COVID-19 CXR Report Proforma
Findings
Normal
COVID-19 not excluded. Correlated with RT-PCR
Classic/Probable COVID-19
Lower lobe and peripheral predominant multiple opacities that are bilateral (>> unilateral)
Indeterminate for COVID-19
Does not fit Classic or Non-COVID-19 descriptors
Non-COVID-19
Pneumothorax / Lobar pneumonia / Pleural effusion(s) / Pulmonary oedema
Other
Quantifying disease
Mild / Moderate / Severe
Other findings
Codes for subsequent Radiology Information System search:
CVCX0 = Normal CVCX1 = Classic CVCX2 = Indeterminate CVCX3 = Non-COVID-19
Please consider case upload to https://bit.ly/BSTICovid19_Database
CXR Examples
Patient 1 36MFever SOB worsening over 8 days ?COVID
Basal and peripheral involvement
Mild
PCR +ve
• Patient 2 75M
• Presents COPD, productive cough ?COVID
• Peripheral and basal consolidation which is bilateral.
• Classic pattern.
• Severe
• PCR subsequently positive
Patient 3. 38F
Classic pattern, severe
PCR +ve
Patient 436 male
Dad COVID +, unwell 11/7, dry cough, SOB, high RR.
Lymphopenia
First swab –ve, repeat swab +ve
Patient 5PCR positive at time of reporting.
This film would normally be reported as not compatible with COVID-19
Patient 840mFeverlow sats ?COVID ?LRTI
Vague opacity but non specific. Reported as normal.
Patient 8CT performed subsequently
RT-PCR subsequently confirmed positive
CT
Sensitivity 85% Specificity 60% -same study
Findings: Peripheral ground glass. Crazy paving. Consolidation. Bronchovascularthickening. Reverse Halos.
Thromboembolism in COVID
• Several centres report increased incidence in an ITU setting. Pooled analysis suggests a figure of about 17%.
• Difficult to study true prevalence. Nottingham approach and study. Local rate about 3% in triage population
• Immunothrombosis versus embolism
• Anticoagulating all patients does not improve survival
• Criteria for diagnosing PE clinically difficult (D-dimer expected to be raised, patients with pneumonitis have similar symptoms)
• Difficult to exclude clinically
Thromboembolism in COVID
• Remember about renal impairment in COVID 19
• The original BSTI/NHSE algorithm remains the main stay of imaging advice, with CTPA reasonable to perform in severely ill Covid-19 patients if the outcome would influence initiation of therapeutic anticoagulation.
• A less severely ill patient with classic Covid-19 on CXR should not trigger a CTPA routinely.
• CTPA in symptomatic patients with Classic Covid-19 on CXR should ideally be reserved for ‘disproportionate hypoxia’, ‘discordant clinical picture’ or a ‘sudden clinical deterioration’.
• This should be mentioned in all CTPA requests.
• A presenting high D-Dimer in a patient with Covid-19, or an elevation/upward trend should not solely be used to trigger a CTPA.
• At all times, patient stability and infection control considerations must be weighed against the benefit of undertaking the CTPA, especially given the higher infectivity of the new variant.
• When reporting CTPA the radiologist should not use the term “PE” for those with just segmental and/or subsegmental changes but describe the changes and then suggest they may represent PE or immunothrombosis (e.g. “a filling defect is noted; whether or not this represents embolus or immunothrombosis is uncertain”).
• https://www.bsti.org.uk/media/resources/files/Rationale_for_CTPA_in_Covid_considerations_F.pdf
Post COVID fibrosis
• Few data.
• The prevalence of post-COVID-19 fibrosis will become apparent in time, but early analysis from patients with COVID-19 on discharge from hospital suggests a high rate of fibrotic lung function abnormalities. Overall, 51 (47%) of 108 patients had impaired gas transfer and 27 (25%) had reduced total lung capacity. This was much worse in patients with severe disease
• Reference below suggests 1/3 with severe COVID-19 pneumonitis have abnormality at 6 months on imaging
• 1). Han X, Fan Y, Alwalid O, Li N, Jia X, Yuan M, Li Y, Cao Y, Gu J, Wu H, Shi H. Six‐month follow-up chest CT findings after severe COVID‐19 pneumonia. Radiology (In Press) Google Scholar
CT
• Examples on Horos
Some take home
messages
References
• BSTI:
• https://www.bsti.org.uk/standards-clinical-guidelines/clinical-guidelines/bsti-nhse-covid-19-radiology-decision-support-tool/
• Radiopedia article:
• https://radiopaedia.org/articles/covid-19-4?lang=gb
• Cochrane review:
• https://www.cochrane.org/CD013639/INFECTN_how-accurate-chest-imaging-diagnosing-covid-19
• Paper on imaging findings:
• https://pubs.rsna.org/doi/10.1148/rg.2020200159
• RSNA COVID resources
• https://www.rsna.org/covid-19