[Assessment of the generalisability of clinical trial results in the Federal Joint Committee].

The assessment of the transferability, sometimes called external validity, of study results is subordinate to the assessment of the internal validity of clinical studies. Although internal and external validity seem to be related they actually are fundamentally different concepts. While assessing the transferability or generalisability of study results effect-modifying factors (e.g., age, gender, qualification of the suppliers, technical equipment) have to be considered. In principle relevant or known effect-modifying factors can be allowed for within the decisions of the Federal Joint Committee (G-BA). This can be demonstrated by the example of acupuncture for chronic low back pain or osteoarthritis of the knee. However, the correct utilisation (and accordingly, effectiveness) of health technologies in everyday practice cannot be influenced by the G-BA. Still it would be desirable to have a scientifically sound, standardised tool available for assessing the external validity of study results.