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A new scoring system can predict whether COVID-19 patients will require invasive mechanical ventilation, researchers report.
The score uses three variables to predict future risk: heart rate; the ratio of oxygen saturation (SpO₂) to fraction of inspired oxygen (FiO₂); and a positive troponin I level.
“What excites us is it’s a really benign tool,” said Muhtadi Alnababteh, MD, from the Medstar Washington Hospital Center in DC. “For the first two variables you only need to look at vital signs, no labs or invasive diagnostics.”
“The third part is a simple lab, which is performed universally and can be done in any hospital,” he told Medscape Medical News. “We know that even rural hospitals can do this.”
For their retrospective analysis, Alnababteh and his colleagues assessed 265 adults with confirmed COVID-19 infection who were admitted to a single tertiary care center in March and April. They looked at demographic characteristics, lab results, and clinical and outcome information.
Ultimately, 54 of these patients required invasive mechanical ventilation.
On multiple-regression analysis, the researchers determined that three variables independently predicted the need for invasive mechanical ventilation.
|Predictors of Mechanical Ventilation|
|Variable||Odds Ratio||P Value|
|Heart rate at admission||1.03||<.001|
|Positive initial troponin level||4.18||<.001|
Calibration of the model was good (Hosmer–Lemeshow score, 6.3; P = .39), as was predictive ability (area under the curve, 0.80).
The risk for invasive mechanical ventilation increased as the number of positive variables increased (P < .001), from 15.4% for those with one positive variable, to 29.0% for those with two, to 60.5% for those with three positive variables.
The team established cutoff points for each variable and developed a points-based scoring system to predict risk.
|Points Allotted for Each Variable That Reaches the Cutoff Threshold|
|SpO₂/FiO₂ < 4.4||3|
|Heart rate > 101 beats per minute||4|
|Troponin > 0 ng/mL||5|
It was an initial surprise that troponin — a cardiac marker — would be a risk factor. “Originally, we thought COVID-19 only affects the lung,” Alnababteh explained during his presentation at CHEST 2020. Later studies, however, showed it can cause myocarditis symptoms.
The case for looking at cardiac markers was made when a study of young athletes who recovered from COVID-19 after experiencing mild or no symptoms showed that 15% showed signs of myocarditis on cardiac MRI.
“If mild COVID disease in young patients caused cardiac injury, you can imagine what it can do to older patients with severe disease,” Alnababteh said.
This tool will help triage patients who are not sick enough for the ICU but are known to be at high risk for ventilation. “It’s one of the biggest decisions you have to make: where do you send your patient? This score helps determine that,” he said.
The researchers are now working to validate the score and evaluate how it performs, he reported.