BACKGROUND: The King-Devick (KD) test measures the speed of rapid number naming, and is postulated to require fast eye movements, attention, language, and possibly other aspects of cognitive functions. While used in multiple sports concussion studies, it has not been applied to the field of movement disorders.

METHODS: Forty-five Parkinson’s disease (PD), 23 essential tremor (ET), and 65 control subjects were studied. Subjects performed two trials of reading out loud single-digit numbers separated by varying spacing on three test cards that were of different formats. The sum time of the faster trial was designated the KD score and compared across the three groups.

RESULTS: PD patients had higher (worse) KD scores, with longer reading times compared to ET and control subjects (66 seconds vs. 49 sec. vs. 52 sec., p < 0.001, adjusting for age and gender). No significant difference was found between ET and control (Δ = -3 seconds, 95% CI: -10 to 4).

CONCLUSIONS: This is the first study of the King-Devick Test in Parkinson’s disease. PD patients were found to have a slower rapid number naming speed compared to controls. This test may be a simple and rapid bedside tool for quantifying correlates of visual and cognitive function in Parkinson’s disease.

Summary Points:

  • Two trials of the K-D Test were administered to individuals with Parkinson’s Disease (PD) and essential tremor (ET) and compared with controls.
  • Those with PD scored significantly worse on the K-D Test compared to those with ET and the control group (adjusting for age and gender).
  • There was no significant difference in scores in the ET group verses control group.
  • The K-D Test may be an effective bedside tool for quantifying aspects of visual and cognitive function in patients with PD.
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