Diagnostic accuracy of subjective dyspnoea in detecting hypoxaemia among outpatients with COVID-19: a retrospective cohort study

  1. Linor Berezin
  2. Alice Zhabokritsky
  3. Nisha Andany
  4. Adrienne K Chan
  5. Jose Estrada-Codecido
  6. Andrea Gershon
  7. Philip W Lam
  8. Jerome A Leis
  9. Scott MacPhee
  10. Samira Mubareka
  11. Andrew E Simor
  12. Nick Daneman

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Abstract

The majority of patients with mild-to-moderate COVID-19 can be managed using virtual care. Dyspnoea is challenging to assess remotely, and the accuracy of subjective dyspnoea measures in capturing hypoxaemia have not been formally evaluated for COVID-19. We explored the accuracy of subjective dyspnoea in diagnosing hypoxaemia in COVID-19 patients.

Methods

This is a retrospective cohort study of consecutive outpatients with COVID-19 who met criteria for home oxygen saturation monitoring at a university-affiliated acute care hospital in Toronto, Canada from 3 April 2020 to 13 September 2020. Dyspnoea measures were treated as diagnostic tests, and we determined their sensitivity (SN), specificity (SP), negative/positive predictive value (NPV/PPV) and positive/negative likelihood ratios (+LR/−LR) for detecting hypoxaemia. In the primary analysis, hypoxaemia was defined by oxygen saturation <95%; the diagnostic accuracy of subjective dyspnoea was also assessed across a range of oxygen saturation cutoffs from 92% to 97%.

Results

During the study period, 89/501 (17.8%) of patients met criteria for home oxygen saturation monitoring, and of these 17/89 (19.1%) were diagnosed with hypoxaemia. The presence/absence of dyspnoea had limited accuracy for diagnosing hypoxaemia, with SN 47% (95% CI 24% to 72%), SP 80% (95% CI 68% to 88%), NPV 86% (95% CI 75% to 93%), PPV 36% (95% CI 18% to 59%), +LR 2.4 (95% CI 1.2 to 4.7) and −LR 0.7 (95% CI 0.4 to 1.1). The SN of dyspnoea was 50% (95% CI 19% to 81%) when a cut-off of < 92% was used to define hypoxaemia. A modified Medical Research Council dyspnoea score >1 (SP 98%, 95% CI 88% to 100%), Roth maximal count <12 (SP 100%, 95% CI 75% to 100%) and Roth counting time <8 s (SP 93%, 95% CI 66% to 100%) had high SP that could be used to rule in hypoxaemia, but displayed low SN (≤50%).

Conclusions

Subjective dyspnoea measures have inadequate accuracy for ruling out hypoxaemia in high-risk patients with COVID-19. Safe home management of patients with COVID-19 should incorporate home oxygenation saturation monitoring.

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  1. Version published to 10.1136/bmjopen-2020-046282
  2. ScreenIT

    SciScore for 10.1101/2020.08.10.20172262: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIRB: This study was approved by the institutional review board at Sunnybrook Health Sciences as minimal risk research, using data collected for routine clinical practice, and the requirement for informed consent was waived.
    Consent: This study was approved by the institutional review board at Sunnybrook Health Sciences as minimal risk research, using data collected for routine clinical practice, and the requirement for informed consent was waived.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    This study has several limitations. The data collected for this study were from patients’ initial pulse oximeter assessment and did not assess whether changes in dyspnea correlate with changes in SpO2 over time. This is a potentially important notion when monitoring patients who are (or are not) becoming increasingly dyspneic while self-isolating in their homes. While the number of patients included was sufficient for the primary analysis, they were insufficient for precise estimates of subgroups stratified by age, presence of lung disease, and date of symptom onset. Additionally, our study was limited to patients who were considered at high risk of severe disease, and it is possible that the diagnostic test characteristics might differ in younger and healthier patients. Lastly, pulse oximeters may have variable accuracy as individuals become increasingly hypoxic and are further impacted by individual patient characteristics; however, a perfect reference standard of invasive blood oxygen measurement would be neither practical nor ethical in the outpatient setting.26 Our findings indicate that subjective dyspnea does not accurately capture hypoxemia in patients with COVID-19. Although some dyspnea scores have high specificity and positive likelihood ratios for identifying hypoxemia, none of these measures have sufficient sensitivity to rule out hypoxemia. Therefore, relying on surrogate measures of dyspnea alone is not sufficient to remotely monitor high-risk outpatients with ...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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  3. Version published to 10.1101/2020.08.10.20172262v1 on medRxiv