Inter-Rater Agreement in the Clinical Diagnosis of Essential Tremor: Data from the NEDICES-2 Pilot Study

BACKGROUND: Our aim was to assess the diagnostic agreement among the neurologists in the Neurological Disorders in Central Spain 2 (NEDICES-2) study; these neurologists were assigning diagnoses of essential tremor (ET) vs. no ET. METHODS: Clinical histories and standardized video-taped neurological examinations of 26 individuals (11 ET, seven Parkinson’s disease, three diagnostically unclear, four normal, one with a tremor disorder other than ET) were provided to seven consultant neurologists, six neurology residents, and five neurology research fellows (18 neurologists total). For each of the 26 individuals, neurologists were asked to assign a diagnosis of “ET” or “no ET” using diagnostic criteria proposed by the Movement Disorders Society (MDS). Inter-rater agreement was assessed both with percent concordance and non-weighted κ statistics. RESULTS: Overall κ was 0.61 (substantial agreement), with no differences between consultant neurologists (κ = 0.60), neurology residents (κ = 0.61), and neurology research fellows (κ = 0.66) in subgroup analyses. Subanalyses of agreement only among those 15 subjects with a previous diagnosis of ET (11 patients) and those with a previous diagnosis of being normal (four individuals) showed an overall κ of 0.51 (moderate agreement). DISCUSSION: In a population-based epidemiological study, substantial agreement was demonstrated for the diagnosis of ET among neurologists of different levels of expertise. However, agreement was lower than that previously reported using the Washington Heights–Inwood Genetic Study of Essential Tremor criteria, and a head-to-head comparison is needed to assess which is the tool of choice in epidemiological research in ET.