Development of the PHASE-Proxy scale for rating drug-related signs and symptoms in severe cognitive impairment

The need for assessment of possible drug-related signs and symptoms in older people with severe cognitive impairment has increased. In 2009, the PHASE-20 rating scale for identifying symptoms possibly related to medication was the first such scale to be found valid and reliable for use with elderly people. In this project, the aim was to develop and examine the psychometric properties and clinical utility of PHASE-Proxy, a similar scale for proxy use in assessing elderly people with cognitive impairment.

Three expert groups revised PHASE-20 into a preliminary proxy version, which was then tested for inter-rater reliability, internal consistency, and content validity. Its clinical usefulness was investigated by pharmacist-led medication reviews. Group interviews and a study-specific questionnaire with nursing home staff were used to investigate the feasibility of use.

The PHASE-Proxy scale had satisfactory levels of inter-rater reliability (Spearman's rank correlation coefficient; r_s = 0.8), and acceptable internal consistency (Cronbach's alpha coefficient; α = 0.73). The factor analysis resulted in a logical solution with seven factors, grouped into two dimensions: signs of emotional distress and signs of physical discomfort. The medication reviews, interviews, and questionnaires also found the proxy scale to be clinically useful, and feasible to use.

The PHASE-Proxy scale appears to be a valid instrument that enables proxies to reliably assess nursing home residents who cannot participate in the assessment, to identify possible drug-related signs and symptoms. It also appears to be clinically useful and feasible for use in this population.