SPP1 and COVID-19: (d) In the multiple logistic regression analyses, the presence of symptoms, dyspnea or the combination of serious symptoms were linked to previously established risk factors, including female gender, increased BMI and pre-existing dyspnea (before the acute disease), while increased plasma OPN levels, female gender and pre-existing dyspnea with m-MRC > 1 were independently associated with severe post-COVID-19 dyspnea (m-MRC > 1).