Repeated false-negative tests delayed diagnosis of COVID-19 in a case with granulomatosis with polyangiitis under maintenance therapy with rituximab and concomitant influenza pneumonia. Issue 3 (15th July 2020) - Hakroush, Samy; Franz, Jonas; Larsen, Jörg; Korsten, Peter; Winkler, Martin Sebastian; Tampe, Björn