A Study Investigating the Inter- and Intra- Rater Reliability of Functional Outcome Measures in Neurofibromatosis 2

Neurofibromatosis 2 (NF2) is an inherited condition that occurs in 1 in 33,000 births; affecting hearing, balance, dizziness and vision primarily related to tumours (schwannomas) in the inner ear or other tumours which develop within the central nervous system. Neuropathy may also be an issue for people with NF2.

The complications of NF2 can lead to varied difficulties with activities of daily living and may impair quality of life. More recently, new pharmacological treatments for NF2 are being trialed which may have the potential to dramatically influence quality of life for people with NF2. Currently, evaluation of treatment effect in NF2 is based on a clinician's neurological assessment and imaging. However, imaging results do not always correlate with clinical and reported functional changes of the individual. Therefore, evaluating the effect of interventions or treatment should include the evaluation of a person's function using standardised outcome measures. The findings from this study will improve the care of people with NF2 by ensuring that we are able to measure functional changes in a person with NF2 with greater confidence, meaning that we can start, continue or cease treatments based on the holistic picture of an individual.

The world confederation of physiotherapists (WCPT) stipulates that standardised outcome measures (SOM) are used to provide a quantitative measure of capability, and to evaluate the impact of treatment on function. There are a wide range of SOM's that evaluate function so a SOM is chosen by the clinician based on the patient's presenting functional difficulty and the scientific credibility of the SOM. Scientific credibility (robustness) is based on scientific properties of the SOM i.e. how stable the SOM is (reliability) and whether it assesses what it is intending to assess (validity). It is important to evaluate each SOM within the target population as variability within that condition, strongly influences the SOM's reliability and validity (de Vel 2011).

At present, functional SOM's have limited scientific and subsequent clinical credibility when used in people with NF2 because their scientific properties have not yet been evaluated within this patient group which means that if they are used clinically or within research, there is an inherent element of doubt when interpreting the SOM's results. The objective of this research team is to create a core set of functional SOM's which have undergone rigorous scientific evaluation so that they can be used in the future for clinical practice and for research purposes in adults with NF2.

This study primarily aims to evaluate three commonly used SOM's for reliability in adults with NF2 (over 16 years of age). The measures chosen for evaluation are the nine hole peg test, the four square step test and the modified clinical test of sensory integration and balance (mCTSIB). Interrater reliability (the test result remains the same when reviewed by different people) and intrarater reliability (the test result remains stable when reviewed twice by the same tester) will be evaluated. From this data, we will be able to calculate the standard error of measurement an additional important scientific characteristics of SOM evaluation. A secondary objective is to correlate SOM objective markers with a subjective disease specific quality of life measure (NFTI-QOL) and self-reported falls rate and near misses. We will also collect data on dynamic visual acuity in this patient group.