Molecular tests have gained a solid position in clinical virology. Developments in molecular diagnostics go rapidly; within a few hours several viruses can be detected in one single, sensitive laboratory test. These developments do raise questions regarding the clinical value of these tests. What does the outcome of a diagnostic test means for the patient, for treatment and additional diagnostic procedures, and preventive measures to reduce further spread of viruses. In this thesis the advantages of molecular diagnostic tests are described by studies into enterovirus 68 , rhinovirus and influenza virus. By combining clinical and epidemiological data with the outcome of viral diagnostic tests, the role of these viruses in causing respiratory...