Seite - 25 - in Applied Interdisciplinary Theory in Health Informatics - Knowledge Base for Practitioners

maximise the information gained. The important point about this perspective is that it provides a rational basis for identifying which test to perform at each stage of an engagement with a patient. It is quite straightforward to map the model in Figure 1 onto the specifics of telegraphy, radio or television broadcasting, and the internet, for example. However, it will be of more interest in the current context if we instantiate the model within a clinical setting. Figure 2. The communication system in a clinical setting. We have actually changed very little in Figure 2 compared with Figure 1: the information source has become the patient’s state; the destination has become the physician who has responsibility for performing the diagnosis of the patient’s state. We do still need to keep the model quite general. The transmitter might be, for example: The patient themselves, in the context of a consultation; A measurement on the patient; A trained physician or nurse examining the patient; The result of a test performed on the patient. Do note the distinction between a message from the patient’s condition that is some deviation from what is normal, and the signal that may be transmitted by the patient themselves or by a physician or nurse examining the patient. We cannot guarantee that the signal is an accurate representation of the original message (or that the transmitter has not missed a message, or even invented a message). The channel might be, for example: A verbal utterance if transmitter and receiver are in the same room; A telephone line; An internet link; A written communication. The task of the receiver is to transcribe the signal into an electronic or written record. Finally, the physician is the end point for a sequence of messages that will progressively inform a medical diagnosis. There are two key points to keep in mind: 1. Any stage in the communication system may lead to loss or distortion of the information in a message as it is transmitted from its source to the physician; 2. Each message will contain a certain amount of information that will inform candidate diagnoses. If we can maximise the amount of information in each message, then we should be able to minimise the number of messages needed in order to reach a confirmed diagnosis. Transmitter Channel Patient’s state Receiver Physician Noise Source message message signal received signal P.Krause / InformationTheoryandMedicalDecisionMaking 25