Exhaled Nitric Oxide test for COVID-19 severity screening
Exhaled Nitric Oxide (FeNO) testing is a widely-used diagnostic tool in the treatment of asthma, where it is used to estimate the extent of inflammation in the airways. Airway inflammation also plays a significant role in the disease progression of severe COVID-19 infections, which suggests that similar testing could play a role in determining the likely course that the disease will take in a patient. At present, the standard means of testing for COVID-19's characteristic inflammatory cascade is a C-reactive protein test, with rapidly rising CRP levels being a strong predictor of subsequent respiratory deterioration. A similar correlation with exhaled Nitric Oxide may exist, potentially offering an additional diagnostic tool that does not require a blood draw for laboratory testing. FeNO testing may also be predictive of otherwise mild COVID-19 cases that result in long-term lung damage.
A recent preprint has shown that Budesonide, a corticosteroid used to treat airway inflammation in asthma patients and the prescription of which is frequently predicated on positive findings in FeNO testing, improves outcomes in COVID-19 patients, further highlighting a possible role for FeNO tests in the screening COVID-19 patients and in determining appropriate treatment options.