ADAMTS13 factor deficiency in severe COVID-19 may not be immune mediated - report from a pilot study.

Background: The assessment of ADAMTS13 factor activity and inhibitor levels was conducted in severe COVID-19 patients as an observational study.
Results: A total of 14 patients were included and the average ADAMTS13 activity level at the time of admission was 28.54±30.74% (range 1.83-86.67%) which was reduced compared to controls (88.09±14.77). Nine patients had reduced ADAMTS13 factor activity (<40%) and 77.7% among them had severe deficiency (<10% activity). ADAMTS13 inhibitor was positive (>15 IU/mL) only in two patients and an overall mean value was 8.15±5.8. Elevated D-Dimer and length of hospital stay had significant correlation with ADAMTS13 activity (-0.247 and 0.306 respectively). No features of thrombotic microangiopathy were observed and hence no plasma exchange was performed.
Conclusion: Reduced ADAMTS13 factor activity without inhibitor development may give a clue to the disease progress in COVID-19.