Urinary L-Type Fatty Acid-Binding Protein Predicts Oxygen Demand of COVID-19 in Initially Mild Cases

Early detection of illness trajectory in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infected patients is crucial for patients and healthcare workers. An effective, noninvasive approach, with simple measurement for decision-making, is necessary in a pandemic to discriminate between high- and low-risk patients, even though both groups may exhibit mild symptoms in the beginning.

To predict COVID-19 disease severity within 10 days, distinguishing cases that will progress to moderate or severe versus mild, patient urinary L-type fatty acid-binding protein (L-FABP) was assayed within 4 days of receiving a diagnosis. The study also examined whether L-FABP point of care (POC) test is helpful in risk screening.

Symptomatic subjects who tested positive for SARS-CoV-2 and were hospitalized were prospectively enrolled at the National Center for Global Health and Medicine (NCGM), Yamanashi Prefectural Central Hospital (YPCH), and Sinai Hospital in Maryland. The outcome of each case was evaluated 7 days after admission and the diagnostic performance of L-FABP was assessed.

Subjects were treated for COVID-19 at public healthcare centers in Japan from January 31, 2020, to January 31, 2021, to NCGM, YPCH, and at Sinai Hospital in Baltimore, MD, during the same period.

The primary outcome was to determine whether urinary L-FABP within 48 hours of admission can predict the patient's severity of COVID-19 1 week later. We obtained demographic data, information on clinical symptoms, radiographic images, and laboratory data.

Diagnostic performance was assessed using receiver operating characteristic analysis. Of the 224 participants in the study, 173 initially had a mild form of COVID-19. The area under the curve (AUC) for a severe outcome was 93.5%. L-FABP POC risk prediction of a severe outcome had an AUC of 88.9%.

Urinary L-FABP can predict patient risk of COVID-19 illness severity. L-FABP POC is implementable for patient management. (ClinicalTrials.gov number, NCT04681040).