Combined values chart and WPI in NSW CTP claims

Combining is different from adding

The combined values approach prevents impairment percentages from exceeding the whole person or region. Two separate numbers may produce a lower final percentage than simple arithmetic addition.

The method decides what can combine

Some body-system methods allow combination; others require a single best method or prohibit combining overlapping impairments. A report should explain the rule, not just show a final number.

Only comparable values should be combined

Regional impairments may need conversion to WPI before being combined with other WPI values. Combining values at the wrong level can distort the result.

Separate injuries

Each impairment must be identified and rated by the correct method before any combination step.

Conversion

Upper extremity, lower extremity or other regional ratings may need conversion to WPI first.

WPI measures permanent impairment. Threshold injury classification asks a different statutory question about the nature of the injury. A person can have an important treatment or work-capacity dispute even where WPI has not yet been assessed, and a WPI result does not decide threshold injury by itself.

Treatment approval is also separate. It usually turns on whether the proposed treatment is accident-related and reasonable and necessary in the circumstances. A diagnosis, operation or WPI percentage does not automatically require the insurer to approve a particular treatment, and treatment approval does not automatically create a common law damages entitlement.

Compare the threshold injury and treatment refusal guides before responding to a mixed insurer decision. Threshold injury guide · Treatment refusal guide

Physical and psychological ratings have a special threshold rule

When deciding whether impairment is greater than 10% in NSW CTP, physical injury ratings cannot be combined with psychiatric or psychological ratings.

Where combined values mistakes appear

Errors often appear before the chart is even used. One value may still be a regional impairment rather than WPI, one injury may duplicate another method, or a psychological percentage may be mixed into a physical threshold calculation. Another common problem is a report that gives the final combined percentage without showing the source values and order of combination. For review purposes, the useful audit is simple: identify each separate rating, confirm it is allowed to stand on its own, convert it correctly, then check whether the Guidelines allow it to be combined for the question being decided.

Combination rule

The report should identify whether values are combined, added, excluded or assessed by one dominant method.

Threshold use

Check whether the final number is being used for damages eligibility or another entitlement issue.

Common traps

• Do not add numbers unless the method expressly says to add.
• Do not combine overlapping impairment methods.
• Do not combine physical and psychological impairment to pass the 10% threshold.
• Do not rely on a final combined number without seeing the source values.

1. List each rated impairment separately.
2. Check whether each value is already WPI or still regional impairment.
3. Trace the combined values step in the report.
4. Ask why any impairment was excluded from combination.
5. If the report skips the method, get the calculation checked.

Assessment source: Motor Accident Guidelines Part 6, clauses 6.36-6.45; AMA4 Combined Values Chart where Part 6 permits combination.

Source note: This page paraphrases the NSW Motor Accident Guidelines and AMA4 impairment framework for general information. It does not reproduce AMA tables or replace medical or legal advice.