Comparing the Responsiveness over Time of Two Tactile Gnosis Tests: Two-Point Discrimination and the STI-Test

Abstract

The purpose of this study was to investigate the responsiveness over time of a new instrument for the assessment of tactile gnosis after nerve repair to the hand - the shape texture identification (STI) test and to compare this to an existing tactile gnosis test - the two-point discrimination test (2PD).

In order to assess the instruments ability to detect clinical change over time a cohort of 32 patients with 37 complete or partial median and/or ulnar nerve repair or double digital nerve repairs were assessed on three occasions over a six months period. Only patients with a touch detection threshold of 2g (Semmes-Weinstein Monofilament 4.31) or less, indicating presence of some protective sensibility, were included in the study. All patients received the same information and were given a standard sensory re-education programme after the initial assessment.

The results from the STI test were analysed longitudinally with the Wilcoxon signed rank test and Standard Response Mean (SRM) was used to estimate the responsiveness and size of change over time. The results were compared to results from the two-point discrimination test.

Between the first and second follow-up the STI-test detected improvements which were statistically significant (p=0.001). An improvement was also noted between the second and third test occasion, however this did not reach statistical significance. Results from the two-point discrimination test showed a flooring effect and change was only detected in the partial nerve repairs, between the first and last assessment.

We conclude that the STI test is sensitive to change and should be used as an alternative to or at least complement the 2PD test when evaluating tactile gnosis after nerve repair.

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