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The Pill Questionnaire may severely underestimate impairments in activities of daily living (ADL) in patients with Parkinson's disease (PD).
Many patients with PD stay cognitively intact, especially if one discounts very mild executive dysfunctions in neuropsychological tests. Notwithstanding the above, it is recognised that increasing disability due to cognitive deficits, that is, dementia, develops in a substantial number of PD patients.1 Affected cognitive domains are variable, often dominated by impairments in executive functions, but may also include impaired visuospatial, constructional attention and memory functions. Point prevalence of dementia associated with PD (PD-D) is roughly 30%, but that number will largely depend on the clinical diagnostic criteria applied. This is where it gets more difficult for the clinician, since these criteria are not yet fully established. To meet this demand, the International Parkinson and Movement Disorder Society (MDS) deployed a Task Force, which proposed formal diagnostic criteria and corresponding recommendations for diagnostic procedures.1 ,2 Maybe the most critical of the proposed diagnostic criteria demands that cognitive impairments are severe enough to impair daily life (see table 1 in both publications).1 ,2 This fine line marks the border between mild cognitive impairment and dementia, and thus is a distinction of great clinical importance. While ADL are more than evidently impaired in some cases, it may be very hard to discriminate the source of ADL impairment (ie, cognitive vs motor). The MDS Task Force proposed to focus on the patient's ability to manage non-motor tasks, such as finances, using pieces of equipment and coping in social situations. These abilities are hard to formally evaluate, but the Task Force also proposed the so-called Pill Questionnaire, a formal and simple assessment of the ability to organise independently the daily distribution of antiparkinsonian medication.2 Importantly, the authors stressed that the validity of the Pill Questionnaire has yet to be investigated. Lee and coworkers have done exactly that.3 They investigated the validity of the Pill Questionnaire as an instrument to establish the essential ‘impaired ADL’ criterion for the diagnosis of PD-D. They did so by statistically comparing the Pill Questionnaire with the clinical judgement of experienced neurologists. The sample was recruited in 12 hospitals and consisted of 284 consecutive patients who developed PD after 50 years of age and had no neuropsychiatric comorbidity other than cognitive decline (eg, stroke or depression). They also excluded patients who developed dementia before or within 1 year after PD onset to avoid recruitment of patients with dementia with Lewy bodies. In essence, the results demonstrated that the Pill Questionnaire might substantially underestimate ADL impairment. About every second patient identified as having ADL impairment through clinical interview was negative according to the Pill Questionnaire. The fact that missed patients had comparatively milder cognitive impairment indicates that the Pill Questionnaire might be insensitive to impairments in types of instrumental ADL unrelated to management of medication. This insight is an important achievement. Unless other studies contradict, Lee and colleagues hereby firmly place this ball back into the court of the MDS Task Force.
Competing interests None.
Provenance and peer review Commissioned; internally peer reviewed.
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