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October 22, 2020
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Simple risk score may predict need for mechanical ventilation in COVID-19

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Researchers developed a novel risk score to predict risk for mechanical ventilation among hospitalized patients with COVID-19.

Thresholds for three common clinical variables were used: admission heart rate, any position initial troponin level and ratio of oxygen saturation to fraction of inspired oxygen (SpO2/FiO2).

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Muhtadi Alnababteh, MD, chief resident at MedStar Washington Hospital Center, and colleagues conducted a retrospective study of adults with laboratory-confirmed COVID-19 who were admitted to the tertiary care center from March 15 to April 15. Among 265 patients, 54 (20.4%) required invasive mechanical ventilation, the overall mean age was 59 years, 55% were men and 75% were Black.

The researchers found that three common clinical variables independently predicted the need for mechanical ventilation in this population:

  • admission heart rate (OR = 1.032; 95% CI, 1.013-1.015; P < .001);
  • SpO2/FiO2 ratio (OR = 0.619; 95% CI, 95% CI, 0.463-0.829; P = .001); and
  • any position initial troponin (OR = 4.18; 95% CI, 1.93-9.036; P < .001).

Alnababteh and colleagues also determined the best cutoff points for two of the variables: admission heart rate higher than 101.5 beats per minute (area under the curve = 0.686; 68.5% sensitivity; 66.4% specificity) and SpO2/FiO2 ratio less than 4.4 (AUC = 0.714; 72.2% sensitivity; 61.6% specificity).

The overall model showed good calibration (Hosmer-Lemeshow test = 6.3; P = .39) and predictive ability (AUC = 0.8), Alnababteh said during the late-breaking abstracts presentation at the virtual CHEST Annual Meeting.

Each of the variables were awarded points to determine risk, he said. SpO2/FiO2 ratio less than 4.4 was associated with three points, heart rate higher than 101.5 beats per minute was associated with four points and any positive troponin was associated with five points. When the researchers logged these values in the model, mechanical ventilation was required in 1.4% of patients with none of the variables, 15% with a single positive variable, 29% with two variables and 60% with all three variables, he said.

“Heart rate, SpO2/FiO2 ratio and troponin predicted the need for invasive mechanical ventilation with good accuracy and provide an easily applied scoring system to determine risk,” Alnababteh said.

The researchers noted several limitations of the study, including its retrospective design and small sample size. Also, most of the patients in this study were Black, so the results may not be generalizable to other populations, Alnababteh said.

The researchers plan to validate this score and examine difference scores in a larger number of patients in a prospective database across the health care system.

Reference:

Alnababteh M, et al. Chest. 2020;doi:10.1016/j.chest.2020.09.009.