The board need not rely solely on medical evidence in making its determination. To cancel a disability retirement allowance, the board must demonstrate that:

(1) The retiree is reasonably able to perform the ordinary duties of his or her former position or a position within the retiree's former rank with average efficiency; and

(2) There has been a material change in the circumstances upon which the retirement was based; and

(3) No other physical or mental disability now prevents the retiree from performing the ordinary duties of his or her position or rank.

The board may not cancel a disability retirement allowance based on a determination that the medical condition was incorrectly diagnosed at the time of the initial disability hearing. If the medical condition for which the retiree was granted disability retirement has improved, but the retiree is still not physically or mentally able to perform his or her duties with average efficiency, the retiree shall continue to receive the disability retirement allowance. The board must send a copy of all determinations and the examination reports and other evidence on which they are based to the department of retirement systems.