Correct and timely diagnosis is the essential first step to achieving ideal health outcomes. Diagnostic error can occur due to wrong test being performed, delayed diagnosis, or lack of appropriate tests. Many common and rare diseases do not have specific diagnostic tests available to assist in clinical decision-making. To address these unmet diagnostic needs with proteomic technologies, my laboratory has worked with clinical collaborators over the past decade in various research projects. This talk will highlight two major areas of diagnostics: the mass spectrometry-based amyloidosis diagnostic test that has helped patients with this rare disorder to receive the right treatment, and the multi-stage development of surveillance blood test for oesophageal cancer.