In the Loop – Vol. 24 | September 2025
QA Insights
Combining Whole Person Impairment figures:
Common areas of confusion
This month, I successfully passed the AMA 5 exam and became a Certified Impairment Rater (CIR). To put my studying to good use, I thought I’d help to answer one of the most common questions we receive in the Quality Assurance department:
Author
Margaret Fekete
Where did the total Whole Person Impairment (WPI) figure come from?
Mr Smith has undergone an Independent Medical Examination (IME) and the subsequent report has just been delivered. Within the report, the expert finds that Mr Smith has three impairments:
● 7% WPI for the injury to his lumbar spine;
● 8% WPI for the amputation of his index finger through the PIP joint; and
● 15% WPI for the injuries to his left lower limb.
The sum of these figures is 30, but the specialist has calculated a 27% WPI; a meaningful difference in figures when it comes to negotiation and settlement.
Knowledge of the WPI calculation process can help you and your team explain reports to clients and assist you with strategic case planning. Rest assured that you may, with confidence, explain to Mr Smith that the figures are calculated according to a formula and the outcome of the report is evidence-based.
How are the WPI percentages calculated?
The AMA Guides to the Evaluation of Permanent Impairment, Fifth Edition (‘the Guides’) state and explain their formula:
To combine any two impairment values, locate the larger of the values on the side of the chart and read along that row until you come to the column indicated by the smaller value at the bottom of the chat. At the intersection of the row and the column is the combined value.
Luckily, the writers of the Guides realised that this is not easy to follow, particularly with multiple figures to combine. In comes the Combined Values Chart, on page 604 of the Guides (sound familiar?). The Guides explain how we use this chart:
To combine any two impairment values, locate the larger of the values on the side of the chart and read along that row until you come to the column indicated by the smaller value at the bottom of the chart. At the intersection of the row and the column is the combined value.
This process is repeated for each WPI figure.
In the case of Mr Smith, we take the 15% WPI for the left lower limb injuries, and combine this with the 8% WPI for the index finger amputation, which intersects at 22% WPI. We then take the 22% WPI and combine it with the 7% WPI for the lumbar spine injury, resulting in a 27% WPI overall.
Here are some further examples:
● 7% combined with 7% = 14% WPI.
● 15% combined with 5% = 19% WPI.
If arithmetic isn’t your strong suit, I’ll share a trick for some quick impairment combinations – where two WPI values are both equal to or less than 7, the total WPI value is the same as the sum.
Why are total WPI figures calculated in this manner?
The total WPI value cannot exceed 100%, therefore the formula provided in the Guides accounts for the effects of multiple impairments and reflects and individual’s overall functional loss. If Ms Citizen had a 60% WPI for amputation through the humerus at the deltoid tubercle level, and a 50% WPI for a hemipelvectomy, she does not have a 110% WPI overall.
Combination is not equal to the sum of WPI figures; each new impairment is applied to the individual’s remaining unimpaired portion, not to the WPI impairments calculated previously. Ms Citizen’s amputations would therefore result in an 80% WPI overall.
Key takeaways:
Impairment ratings are not raw numbers to be added to infinite; rather, they are proportional reflections of loss.
Understanding the Guides will aid you in your practise, whether it helps you explain a WPI figure to your client, better prepares you to defend an expert’s report by demonstrating its compliance with the Guides, or allows you to spot when an expert report may be inconsistent with the Guides and require review.
