Systematic evaluation of rating scales for drug-induced parkinsonism and recommendations for future research

OBJECTIVE: Drug-induced parkinsonism (DIP) is one of the most common adverse effects of antipsychotic agents. The limited agreement about which rating scale should be used in clinical practice to assess DIP prompted us to review the feasibility and the psychometric qualities of the available instruments. METHODS: The PubMed and EMBASE databases were searched in November 2008 using the terms "parkinsonism," "scale," and "drug induced" to identify instruments used to measure DIP. Then, the literature was searched for studies investigating the use and psychometric properties of each identified instrument. Outcome measures included feasibility, validity (including appropriateness of used reference test), and reliability (internal consistency and interrater and intrarater reliability). RESULTS: Seventeen rating scales were identified, each with a different representation of the concept of parkinsonism. The Simpson Angus Scale (SAS) was used the most, followed by the Extrapyramidal Symptom Rating Scale. There were limited psychometric data, especially regarding validity, available for any scale. The SAS, the Drug-Induced Extrapyramidal Scale, and the parkinsonism subscale of the Schedule for the Assessment of Drug-Induced Movement Disorders, which is identical to the St Hans Rating Scale for Extrapyramidal Syndromes, seemed to have moderate to good reliability and acceptable validity. The time-consuming nature of the Schedule for the Assessment of Drug-Induced Movement Disorders would make it less useful in daily practice. CONCLUSIONS: Although various scales are used to assess DIP, few have been evaluated for validity and reliability. The SAS, St Hans Rating Scale for Extrapyramidal Syndromes, and Drug-Induced Extrapyramidal Scale seem to be the most valid, reliable, and easy-to-use instruments to evaluate DIP in clinical practice.