The upgoing thumb sign: An interobserver/intraobserver reliability study

The upgoing thumb sign as a subtle clinical finding of upper motor neuron involvement has been frequently reported in patients with TIAs and minor strokes. This study was designed to show the method of examination and interpretation and the interobserver/intraobserver reliability.

The thumb sign was elicited in TIA/minor strokes or stroke mimics. After obtaining the participant's permission, the examinations were recorded. Two independent neurologists reviewed all patients for the possibility of an upgoing thumb sign. After 1 hour education about the definition of an upgoing thumb sign to a group of stroke fellows, nurse practitioners, and a research secretary, the videos were reviewed and the participants rated the thumb sign independently. The intraobserver reliability was assessed after 3 months by rating the same videos.

The interobserver reliability among 9 raters showed an overall agreement of 0.83 and fixed-marginal kappa of 0.66. The same videos were reviewed by the observers after 3 months with a similar level of agreement (percent of overall agreement 0.84, fixed-marginal kappa 0.66) and a substantial to almost perfect level of intraobserver concordance (mean 0.86; SD 0.08; median 0.90; interquartile range 25-75, 0.8, 0.95).

The upgoing thumb sign is a subtle upper limb neurologic finding, with a high level of interobserver and intraobserver reliability. The test is easy to perform and can be interpreted accurately.