Medical practitioners guide to permanent impairment assessment

This information bulletin has been developed to assist medical practitioners who undertake permanent impairment assessments/reassessments (for any assessment conducted from 1 September 2017) which are covered in Sections 70 to 72 of the Return to Work Act 1986 (the Act) of the Northern Territory workers compensation scheme.


Section 71 of the Act provides a mechanism by which workers may receive a lump sum payment for compensable injuries or illness which result in a permanent impairment.  This payment is in addition to any other entitlement a worker may have and does not finalise a claim.

When considering undertaking permanent impairment assessments, the medical practitioner should feel confident that their experience, training and skills will lead to a balanced assessment.

For the purposes of the definition of permanent impairment in Section 70 of the Act, permanent impairment means an impairment or impairments assessed in accordance with the Guides approved by the Work Health Authority as being an impairment, or a combination of impairments, of not less than 5% of the whole person. The current approved guides are the NT WorkSafe Guidelines for the Evaluation of Permanent Impairment (hereafter referred to as the Approved Guides).

The Approved Guides adopt the fifth edition of the American Medical Association’s Guides to the Evaluation of Permanent Impairment (AMA5) in most cases. Where there is any deviation with AMA5 the difference is defined in the Approved Guides and the procedures contained in the Approved Guides are to prevail.

The Approved Guides provide a structured set of medical criteria to establish medical ratings of permanent impairment.

It is important to note that a permanent impairment rating is not the same as a disability rating. Permanent medical impairment is related directly to the health status of the individual, whereas disability can only be determined within the context of the personal, social, or occupational demands that the individual is unable to meet as a result of the impairment.

Assessment Procedure

Before medical evaluation is undertaken to determine a percentage level of permanent impairment, the medical practitioner should review the Introduction, parts 2 & 3, of the Approved Guides and the whole chapter which is applicable to the condition, in order to:

  • ascertain the methodology involved
  • the nature of the particular criteria, and,
  • determine the extent of the examination necessary to obtain enough clinical information to rate the impairment.

Please note if publications other than the Approved Guides are referenced in the text of the assessment report it may render the assessment invalid.

The Report

A report of the evaluation of permanent impairment should be accurate, comprehensive and fair. It should clearly address the question/s being asked of the assessor. In general, the assessor will be requested to address issues of:

  • current clinical status;
  • the basis for determining maximum medical improvement;
  • the degree of permanent impairment that results from the injury/condition; and
  • the proportion of permanent impairment due to any previous injury, pre-existing condition or abnormality, if applicable.The report should contain factual information based on all available medical information and results of investigations, the assessor’s own history taking and clinical examination. The other reports or investigations that are relied upon in arriving at an opinion should be appropriately referenced in the assessor’s report.As the Approved Guides are to be used to assess permanent impairment, the report of the evaluation should provide a rationale consistent with the methodology and content of the Approved Guides. It should include a comparison of the key findings of the evaluation with the impairment criteria in the Approved Guides. If the evaluation was conducted in the absence of any pertinent data or information, the assessor should indicate how the impairment rating was determined with limited data.The assessed degree of impairment is to be expressed as a % of whole person impairment (WPI).The report should include a conclusion of the assessor, including the final % WPI.

Reassessment Procedure – Medical Panel Reports

A person aggrieved by the assessment of the level of permanent impairment (a worker, an employer or insurer) may apply to NT WorkSafe for a reassessment.  NT WorkSafe will arrange for a reassessment by a panel of three (3) medical practitioners. One panel member will be appointed as chairperson of the panel. The Approved Guides for assessments also applies to the reassessment process.

Upon conclusion of the examinations by the three medical practitioners, the panel is required to submit a single report. This is usually written by the chairperson. The wording of the report in general is to reflect that it is a consensus of the three medical practitioners and not the opinion of an individual member of the panel.  The report may be signed by either the chairperson or all three panel members.

Individual opinions can be used within the body of the report where there is more than one injury or disease to be reassessed and these require the use of the Combined Values Chart in AMA5 to achieve an overall percentage figure.

If the panel believes that there are aspects of the injury or disease that may require the expertise of another specialist or further examinations (e.g. MRI, X-rays), the panel Chairperson should contact NT WorkSafe on 1800 250 713.

The panel’s assessment of the level of permanent impairment is final.

Contact us

For further information please contact us on 1800 250 713, via email at or go to the NT WorkSafe website at

Medical Practitioners guide to Permanent Impairment Assessment (25 August 2021)