Feasibility and validity of a modified finger-nose-finger test.

In essential tremor (ET) research, it is important to obtain standardized, objective data on tremor severity. Often, it is not possible to carry out in-person or videotaped neurological examinations. In place of these, handwriting samples can be collected, but they do not capture all of the variance in tremor severity. Although additional tests of tremor severity (finger-nose-finger [FNF] test) might be of use, these would need to be modified to allow ET patients to mail their results to the study investigator for rating. We modified the standard FNF test (sFNF) by asking subjects to hold a pen during this activity and mark a paper target. The purpose of this report was to determine whether the modified FNF (mFNF) test was feasible and valid. Of 70 subjects, 65 (92.9%) were able to complete the mFNF, demonstrating that it was feasible. The scores of the mFNF correlated highly with those of the sFNF (r = 0.56-0.85; all P < 0.001), indicating the mFNF is a valid measure of tremor severity. In addition, using the regression equation, sFNF = 0.174(mFNF) + 0.743, a sFNF score can be derived easily from the mFNF score. The mFNF may be used to collect valuable data on tremor severity in pathological, genetic, and epidemiological field studies of ET, in which in-person or videotaped neurological examinations are not possible.