The current invention pertains to electrochemical biosensors. The electrochemical biosensor of the current invention comprises: a) a sensing electrode having attached to its surface a binding agent capable of specifically binding to the analyte to form a binding agent-analyte complex and wherein the binding of the analyte to the binding agent alters the electron transfer properties at the sensing electrode surface thereby providing a change in the electrochemical response at the sensing electrode surface proportional to the number of binding agent-analyte complexes, and b) a test equipment capable of measuring the electrochemical response at the sensing electrode surface. The binding agent can be a binding protein, an antibody, or an aptamer, and the analyte can be a biomolecule. Accordingly, the current invention provides a method of detecting the presence or assessing the likelihood of development of a disease associated with an abnormal level of a biomolecule in a subject.