The 32-year-old admitted to her A-sample positive last week leading to Parkhotel-Valkenburg suspending her. The Belgian was due to join Mitchelton-Scott for the 2020 season after wining the Brabantse Pijl and being awarded the Flandrienne of the year prize for her 2019 road season. Now she faces a battle to explain the presence of the steroid in her urine. She risks a ban of up to four years if found guilty of doping.
"We have made the decision to have the B-sample checked," confirmed her partner and former cyclist Bart De Clercq according to report in Belgian media. "We do not expect much from it. The chance that something else will come out is small but we want to use all means to prove Sofie's innocence.
"We are full of questions. How did she come to that positive doping test? Did contaminated food supplements form the basis of it? We did everything to always work with reliable products. How did we end up in this plight? We're going to do everything to prove her innocence. We're trying to disentangle the entire thing in silence, no matter how difficult that is.
"Sofie feels super bad and we try to stay out of the spotlights as much as possible," De Clercq added protectively. "We don't know when we'll know the result of B-sample, we don’t have any experience with all these things. We would like to know as soon as possible because our search for the unknown continues."
De Vuyst's doping control was an out of competition test on September 18, 2019, the week prior to the World Championships. She admitted to the positive but pleaded her innocence.
"This is a message I never wanted to write. To my astonishment, I received the message yesterday that I tested positive for 'exogenous steroids' during an out-of-competition test on September 18," De Vuyst wrote on her Facebook page according to Sporza.
"For me, ethical and responsible 'clean' sports have always been paramount. I am therefore completely in the dark as to how this could have happened. I am completely devastated, the worst possible nightmare has happened to me."
De Vuyst says she will try everything to clear her name, and regrets the news tarnishing the sport and her team.