Comparing three screening tools for drug-induced parkinsonism in patients with advanced schizophrenia: a pilot study

Drug-induced parkinsonism (DIP) is seen in one third of patients exposed to antipsychotic drugs and may lead to complications related to dysphagia and falls. Aside from skilled neurological examination, no tool has been validated to facilitate detection and follow-up.

In this pilot study, three validated screening instruments were tested in an age-biased cohort of schizophrenia patients, including four items of the Liverpool University Neuroleptic Side-Effects Rating Scale (LUNSERS) and two brief questionnaires designed for community survey of parkinsonism.

Fifty-six subjects living with chronic schizophrenia between 50 and 75 years of age underwent a motor evaluation along the original Unified Parkinson's Disease Rating Scale-section III and answered questions along the selected screening instruments, and results compared to those of 16 patients with Parkinson's disease (PD) and 15 neurologically unimpaired volunteers. Odds ratios, sensitivity, specificity, and their 95% confidence intervals, were calculated.

All three screening instruments correctly identified the PD state and distinguished PD from healthy participants. Eighteen (32%) schizophrenic patients displayed objective motor signs of parkinsonism. A single item of the LUNSERS (shakiness) significantly distinguished DIP from DIP-free patients, with a sensitivity of 61.1% and a specificity of 83.3%. The positive predictive value was 63.5% and the negative predictive value was 81.9%. The two other screening methods showed insufficient predictive value.

Apart from a single query on shakiness, none of the tools examined were adequate to screen for DIP in patients treated for schizophrenia. A different instrument is necessary to monitor this important adverse effect in schizophrenia.