Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder for which relatively few alternative anticoagulants have undergone prospective evaluation as therapeutic agents. Accordingly, one seeks to learn as much as possible from those studies that have been performed. In this issue of CHEST (see page 1407), Lewis and colleagues1– report a secondary analysis of the prospective cohort studies2–3 of argatroban that led to regulatory approval of this direct thrombin inhibitor (DTI) for the treatment of HIT with or without thrombosis. Should we pay attention to secondary analyses of prospective studies? Yes.