TABLE 3.

Modified version of the OHAT predefined algorithm.

Tier 1	Study must be rated as ‘definitely low’ ++ or ‘probably low’ + risk of bias for all key criteria AND have most other applicable criteria rated as ‘definitely low’ ++ or ‘probably low’ + risk of bias	Low RoB
Tier 2	Study does not meet criteria for Tier 1 or Tier 3	Moderate RoB
Tier 3	Study must be rated as ‘definitely high’ −− or ‘probably high’ –/NR risk of bias for most (at least two) key criteria AND have most other applicable criteria rated as ‘definitely high’ −− or ‘probably high’ –/NR risk of bias	High RoB