Administrative practice document: Weighing of medical evidence

Note: This is not a policy; it is supplementary information to illustrate how the WSIB will administer the Workplace Safety and Insurance Act, 1997, (WSIA) and Policy 11-01-02, Decision-Making in practice. If there is a conflict between this information and the WSIA and/or WSIB pol-icy, the decision-maker will rely on the WSIA and/or WSIB policy.


Decision-makers at the WSIB decide entitlement to benefits and services under the Workplace Safety and Insurance Act (WSIA). Decision-makers collect information and weigh evidence to make adjudicative decisions at the initial entitlement stage and throughout the life of a claim.

We receive medical and clinical information from a number of health care professionals who assess and treat an injury or illness based on their scope of practice. While the clinical findings are usually comparable, the interpretation of those findings among the health care professionals involved in a case may vary. This can lead to variation in the description of, or a difference of opinion on diagnosis, prognosis, treatment, causation, and the persons’ functional abilities or physical precautions. Communication with the health care professional may clarify and help integrate clinical and functional information from various sources, and address gaps in medical documentation received. The challenge for the decision-maker is to consider all of this information and weigh it appropriately.

Decisions are based on the way medical information is interpreted and weighed. This document focuses on the weighing of medical evidence in the decision-making process. For the purpose of this document, reference to ‘medical’ information includes ‘clinical’ information.

Key principles

  • Adjudication is the process used to determine entitlement to benefits and services under the WSIA. 
  • A decision-maker is the person who makes decisions regarding entitlement. 
  • Decision-makers gather relevant information and weigh evidence in order to make adjudicative decisions. 
  • People are entitled to receive benefits that result from a work-related injury or illness. 
  • When determining initial entitlement, we establish whether an injury or illness is work-related. Decision-makers continue to evaluate the work-relatedness of an injured or ill person’s ongoing impairment and treatment throughout the claim.
  • The WSIB determines ongoing entitlement based on the causation standard of “significant contributing factor” as outlined in Policy 15-02-03, Pre-existing Conditions
  • The WSIB makes its decisions based on the merits and justice of each case.
  • When the evidence for and against an issue relating to a claim are equal, the benefit of doubt is given to the injured or ill person. 


Decision-makers gather all case-related information to make entitlement and case management decisions. Health care professionals involved in the injured or ill person’s care provide medical reports. We make all reasonable attempts to obtain any missing information so that relevant information is available throughout the adjudicative process. 

We provide wage-loss benefits, medical coverage and support to help people get back to work after a work-related injury or illness. Decision-makers are responsible for collecting the information needed to address and decide all issues that have a bearing on entitlement. Issues that may arise during the life of a claim that require an adjudicative decision include, but are not limited to: 

  • a change in the diagnosis of the work-related injury or illness
  • new area of injury
  • secondary conditions
  • recurrence
  • evidence of ongoing work-related impairment
  • disputes about job suitability
  • treatment required

Decisions relating to medical issues are based primarily on the information and opinions received from the treating health care professional(s). Health care professionals include physicians, surgeons, physiotherapists, chiropractors and registered nurses (extended class). Decision-makers review medical information submitted to the WSIB for completeness and clarity. They continuously assess the medical information to monitor an injured or ill person’s recovery and ongoing work-related impairment.

Determining relevant evidence

The information and medical reports received in a claim are about the work-related injury or illness starting from the date of injury. Occasionally, the WSIB receives information about medical conditions that are not directly related to the work-related injury or illness. Whether or not this information is relevant depends on the circumstances of each case. 

There are also situations where decision-makers request pre-injury medical records for adjudicative decisions. Pre-injury medical records or chart notes are required when determining entitlement for the following: 

  • psycho-traumatic disability or chronic pain disability 
  • ongoing impairment when a pre-existing condition affecting the same area of the body or system as the work-related injury or illness may be contributing to ongoing impairment 

Privacy is a key priority at the WSIB and decision-makers must determine the need to request any particular medical information as well the relevance of all claim-related information. Where a document contains both relevant and non-relevant information, the non-relevant information is redacted from the document. 

We consider all relevant information to reach a decision and retain information that is determined relevant to any claim decisions in the file records. 

WSIB health care programs and services

We have established health care programs integrating community and hospital-based services to collaborate and communicate between health care professionals. WSIB health care programs and services provide people with fast access to specialized health care to support their primary health care professional and WSIB decision-makers with diagnosis, causation, and treatment recommendations. The programs provide quality care and help people in their recovery from the work-related injury or illness. These programs include: 

Community mental health program

The community mental health program provides timely access to psychological assessment and evidence-based, outcome-focused treatment services. The program provides a structured approach for service delivery in several phases, including intake/pre-authorization, assessment and treatment blocks, with corresponding reporting requirements, and with set reporting templates and blocked fee payments. Reports provide information such as outcome measures used to inform recovery and return-to-work planning.

Programs of care

Programs of care are three stand-alone evidence-based health care programs that are available for most common musculoskeletal injuries and specific illnesses, such as mild traumatic brain injury and noise-induced hearing loss.

Hospital-based programs

We provide timely access to high quality hospital based, multidisciplinary assessments and services. A virtual enhanced assessment program would be used if there is early indication of barriers to recovery and return-to-work. An occupational physician expert completes the assessment and supports return-to-work planning in collaboration with us when safe and appropriate. 

The Occupational Health Assessment Program (OHAP) facilitates a clear, coordinated care path by providing occupational focused assessment and case consult services for people with workplace injuries and illnesses. Types of medical assessments include musculoskeletal assessment, mild traumatic brain injury assessment, general medical assessment and medication review and follow-up occupational health assessment. The Occupational Health Assessment Program case consult offers quality medical opinions to help improve recovery and return-to-work outcomes for people with work-related injuries or illness.

The COVID Assessment Program uses the Occupational Health Assessment Program general medical assessment. 

Specialty Programs provide timely access to expert specialists for people with work-related injuries or illnesses. These programs specialize in recovery and achieving a healthy and safe return to work by conducting an assessment and providing interdisciplinary treatment for more complex injuries and illnesses. For example, an integrated function and pain management, psychological support and expedited access to surgery so people can have a coordinated recovery plan.

There are eight Specialty Programs people can access across the province:

  • Amputee, prosthetics and custom orthopedic shoes
  • Burns
  • Back and neck
  • Lower extremity (including foot and ankle, and hip and knee programs)
  • Upper extremity (including hand and wrist, and shoulder and elbow programs)
  • Mental health
    • inclusive of a pilot program specific for first responders
  • Neurology
  • Occupational disease

WSIB Return-to-Work Specialists help people and their employers develop a plan that supports safe return to work.

Physician's role

Decision-makers use the
 as a guide on the treating physician’s role in helping people return to work after an illness or injury. The treating physician’s role is to diagnose and treat the illness or injury, advise, support, provide and communicate information to the injured or ill person and their employer and to work closely with health care professionals to facilitate a safe and timely return to the most productive employment possible. Fulfilling this role requires the treating physician to understand the injured or ill person’s roles in the family and the workplace. It requires the treating physician to recognize and support the employee-employer relationship and the primary importance of this relationship in the return to work. Finally, it requires the treating physician to have a good understanding of the potential roles of a return-to-work coordinator and of other health care professionals and employment personnel in assisting and promoting the return to work.

The Canadian Medical Association recognizes the importance of people returning to all possible functional activities relevant to their life as soon as possible after an injury or illness. The treating physician should encourage a return to function and work as soon as possible after an illness or injury. A safe and timely return to work benefits the employee and their family by enhancing recovery and reducing disability.

It is the role of the decision-maker to use the functional information provided to make decisions about the person’s ability to work.

Our health care programs and services provide an injured or ill person with faster access to specialized and integrated health care. The programs make recommendations that incorporate recovery and return-to-work planning and enhanced communication, making a common understanding of the recommendations, and enabling us to provide timely benefits and services.

Weighing of medical information

We receive medical information relating to the case from a variety of health care professionals, including the programs and services noted above. The decision-maker assesses and weighs each report to reach a decision. The Nurse Consultant involved in health care decisions may be engaged to help identify missing medical information or to help understand medical findings in the file.

Where decision-making is impeded by a lack of pertinent medical information, or by varied opinions from treating health care professionals, the decision-maker may consider a referral to the programs and services offered through the WSIB.

An Occupational Health Assessment Program case consult offers quality medical opinions to help improve recovery and return-to-work outcomes for people with work-related injuries or illness. There are three types of case consult services: general, occupational disease and specialty, all performed by physician specialists.

Communication with treating health care professionals 

Decision-makers make sure all available and relevant information is on file, particularly medical information from the treating health care professional. 

Decision-makers or Nurse Consultants make reasonable attempts to contact the injured or ill person’s treating health care professional to get additional or outstanding information when their recommendations or opinion:

  • does not provide supporting medical findings, or 
  • differ from the recommendations or opinions of other health care professionals involved in the case, or 
  • the treating health care professional has not provided an opinion or recommendation on the issue and a referral for an Occupational Health Assessment Program case consult is being considered. 

Decision-makers or Nurse Consultants advise the treating health care professional when there is a referral for an assessment or an Occupational Health Assessment Program case consult. 

When an Occupational Health Assessment Program needs to consult with the treating physician, the Occupational Health Assessment Program will arrange this. 

When referring a file to one of the WSIB’s contracted programs and services such as an Occupational Health Assessment Program case consult, the decision-maker must outline the details of the case, including the accepted incident history, exposure details or mechanics of the work that may be responsible for the injury or illness or the accepted diagnosis. They must also determine the issues they need help with and frame their questions to the case consult physician or other WSIB assessment service in a clear and objective way.

The following is a list of some points the decision-maker may consider when weighing medical evidence and opinions:

  • The health care professional’s access to all the relevant medical records, including diagnostic reports available to review in order to obtain a complete understanding of the person’s relevant medical history and the injury process involved 
  • Timeliness of the medical examination in relation to the issue at hand. 
  • Degree of the health professional’s knowledge of past and present medical history and its impact on the medical opinion. 
  • Extent of the health professional’s knowledge and understanding of the injured or ill person’s employment environment in relation to ongoing impairment.
  • Expertise of those offering an opinion and relevance to the issue. Reference to relevant medical literature that supports the opinion and recommendations.
  • Evidence or opinion based on an examination of the injured or ill person. Evaluation of the person’s complaints and symptoms relative to the medical findings.
  • Well-explained and logical conclusion of opinion, including supporting medical findings.

The significance of these factors is dependent on the individual circumstances. Even after weighing the medical evidence, based on the considerations noted above, there may still be opposing opinions that the decision-maker determines to be of equal weight. In these cases, the equally weighed medical opinions are assessed together with all other relevant information and weighed to make a decision.

The “Benefit of Doubt” is an adjudicative principle outlined in s.119 (2) of the WSIA. This principle is used where the evidence for or against a particular result is approximately equal in weight, with the benefit of doubt given to the injured or ill person.

The “Benefit of Doubt” principle is not applied to the weighing of the medical evidence or to conflicting medical opinions of equal weight in order to give greater weight to the opinion that favours the injured or ill person. When the body of all of the evidence for and against a particular outcome is approximately equal in weight, then the principle is applied. It is always the decision-maker who makes a benefit of doubt ruling.

Communication of decisions

Wherever possible, we communicate all adjudicative decisions verbally to the workplace parties and then confirm in writing. The decision letter must:

  • identify the issue decided,
  • provide a summary of the facts of the case,
  • provide the entitlement rules that apply to the issue (legislative or policy criteria, or standards),
  • provide the rationale for the decision reached, explaining how the entitlement rules were or were not met,
  • reference only evidence that is relevant to the decision, and
  • include the timeframe for appealing the decision for all adverse decisions.

We communicate decisions in plain language to make sure everyone involved understands the decision and reasons for it. We outline the relevant evidence considered in decision-making.  Where the decision-maker must weigh medical information or opinions that are different or appear to conflict, the decision letter includes an explanation of the relative weight of the evidence. The explanation indicates whether the evidence or opinion was accepted or not, and the reasons the evidence or opinion was given more or less weight.


All decisions are based on the information relevant to the issue being decided. Where medical information is relevant, the decision is based on information received from the treating health care professionals as well as all other sources of medical information, including WSIB health care programs and services.

Decisions aren’t made in the absence of pertinent information – including medical reports from all health care professionals, unless all reasonable attempts to get the missing documents have failed. Where there is varied or differing medical information or opinions, we make effort to understand and integrate the information or reconcile differences. This may include contacting the health care professional. If required, a medical opinion, response to specific questions posed by the case management team, and/or physician-to-physician communication is requested through an Occupational Health Assessment Program case consult, or an appropriate program or service from the WSIB health care continuum.

Evidence or opinions that are not accepted or are given less weight are identified and the reasons for the decision-maker’s assessment of their relative weight is explained.

Document history: 

September 2023 - reviewed

May 2017 – revised to enhance direction on communication with workers’ treating health care professionals (page 5)

March 2015 – replaces Best Approaches Guide, Weighing of Medical Evidence, October 2005.

Scheduled review: 

September 2028