California Self‑Insurance Plans (SIP) Exam 2026 - Free SIP Practice Questions and Study Guide

Causation is the factor used because impairment ratings with pre-existing disabilities are determined by apportioning how much of the impairment comes from the industrial injury versus what was already present. The physician uses the relationship between the injury and the resulting impairment to decide what portion, if any, is caused or worsened by the work incident. If a pre-existing condition accounts for some impairment, that portion is not counted as due to the current injury, while the portion actually caused by the injury is included in the rating.

Medical history alone without physician input isn’t enough to establish this apportionment, and economic loss isn’t related to how impairment is rated. Vision correction status isn’t the general determinant for impairment when considering pre-existing disabilities, unless specifically relevant to a vision impairment calculation.