In this prospective study we used liquid chromatography-tandem mass spectrometry (LC-MSMS) to quantify equilibrium peptide levels (Ang I-IV, Ang 1–7, Ang 1–5) (RAS fingerprint) and active ACE and ACE2 in order to identify their implications for prognosis in COVID-19 patients. The gene discussed is ACE; the disease is COVID-19.