Reliability and validity of a new method of nurse-led assessment of trismus.

Our aim was to develop a way of measuring trismus and evaluating it in terms of reliability and validity for use by nurses who care for patients with head and neck cancer. We developed a method from existing resources and tested it for interoperator reliability and validity against a "gold standard". We showed that within the variables outlined, nursing staff could use it after minimal training to identify patients broadly as being "at risk", "low risk", or having "normal mouth opening". Interexaminer reliability was poor. There was a trend towards a group of people having reasonable interexaminer reliability, and this same group showed consistency towards the gold standard. Nurses' accuracy and consistency in using a simple method of assessing trismus depends on more than the method used, and neither validity nor reliability can be assumed. The accurate assessment of trismus for comparison across studies is complex, and future research must define exactly what method was used.