Hite et al. make two recommendations when performing a test of tandem stance:

"(1) when providing initial support to stabilize, document this support along with the hold time to allow appropriate comparisons to be made both within and across individuals

(2) when testing individuals who can stabilize without initial support, a maximum hold time of 30 seconds or longer may be preferred to a 10-second cap.

The first recommendation may better characterize people with lower balance and mobility function, and the latter recommendation recommendation may uncover subtle but potentially meaningftil deficits in individuals with higher functioning."

Hile ES, Brach JS, Perera S, Wert DM, VanSwearingen JM, Studenski SA. (2012). Interpreting the Need for Initial Support to Perform Tandem Stance Tests of Balance. PTJ 92(10): 1316-1328.