Clinical Diagnostic Error in Primary Care – Understanding the Harm

By Ruth L Stewart, BA, RN, MHA, CHE | Published July 20, 2022

When an individual interacts with the healthcare system, that person expects to receive safe, high-quality care. Unfortunately, inadvertent harm – a diagnostic error – may occur at any point along the continuum of patient care. Diagnostic error may cause avoidable illness, injury, disability and even death. Although hard data on the prevalence of diagnostic error is sparse, the U.S. Institute of Medicine (IOM) estimates that a person will experience at least one consequential diagnostic error in her or his lifetime1.


Diagnostic errors – delayed or inaccurate diagnoses – occur in all healthcare settings, including primary care (non-acute, community-based care delivered by a range of healthcare providers [HCPs]), which is regarded as a high-risk setting for the commission of a diagnostic error. The World Health Organization (WHO) “Diagnostic Errors” report2 and other publications consider diagnostic errors a high-priority problem in primary care because the majority of clinical encounters occur in primary care3. The primary care provider (e.g., physician, nurse practitioner, naturopathic doctor, etc.) is the patient’s first point of contact with and entry point into the healthcare system, which is why correct diagnosis in primary care is important. WHO considers primary care to be the foundation of the healthcare system.


Understanding Diagnostic Error

For the purposes of this document, WHO’s definition of diagnostic error will be used:

“A diagnostic error emerges when a diagnosis is missed, inappropriately delayed or is wrong.

Diagnoses can be completely missed (cancer missed despite symptoms), wrong (patients told they have one diagnosis when there is evidence of another) or delayed (abnormal test result suggestive of cancer, but no one has told the patient).”4


Incidence of Diagnostic Error

Neither Canada nor the U.S. has hard data on the prevalence of diagnostic error in primary care. A Canadian study of the incidence of patient harm was limited to data specific to hospitalized patients5. From an analysis of the study’s data, it was determined that harm occurred in one in five of 138,000 hospitalizations6. The study did not capture data on misdiagnosis as an element causing patient harm7.


Why Diagnostic Error Occurs in Primary Care

Although the majority of patients have positive interactions with primary care, diagnostic error may occur during any clinical encounter (appointment) a patient has with a primary care provider. Factors that contribute to diagnostic error include, but are not limited, to:


The patient’s symptoms do not fit the usual symptoms (e.g., right and not left arm pain associated with a heart attack) of a known medical condition


  • Non-specific symptoms such as a cough that are associated with several medical conditions
  • The patient’s symptoms are not taken seriously
  • The medical condition is infrequent or rare (e.g., monkeypox)
  • The HCP’s failure to perform a physical examination
  • Minimization of women’s complaints, leading to gender disparities in diagnosis (e.g., heart attack)
  • The family of a cognitively impaired individual or child is unable to provide a clear patient history/symptoms
  • Failure to order appropriate diagnostic tests


A number of non-clinical variables may contribute to a diagnostic error, including:


  • The brevity of the typical patient appointment
  • A patient’s limited proficiency in English
  • The provider is pressed for time due to the patient backlog in the waiting room
  • Provider inattention/distraction (e.g., documenting clinical notes on a computer while the patient is speaking)
  • Virtual care (no physical examination) for all clinical patient visits


Strategies to Reduce the Risk of Diagnostic Error

An analysis of diagnostic-related malpractice claims in the U.S. revealed that 57% of errors occur in primary and ambulatory care, with cancer, heart disease and orthopedic injury as the top three missed diagnoses9. Diagnostic errors may occur in commonly encountered routine and infrequent/rare conditions.


Four types of information-gathering activities have been identified in the diagnostic process10:


  • Taking a clinical history and patient interview
  • Performing a physical exam
  • Obtaining diagnostic testing
  • Sending a patient for referrals or consultations


While there is no one way to prevent diagnostic error in primary care, providers can reduce error within their practice by adopting the following strategies:


  • Listening carefully to the reason the patient is seeking clinical care, without interrupting
  • Conducting regular physical examinations when following a patient for a known medical condition to check for changes that occur over time
  • Reconsidering a diagnosis when a patient’s condition is deteriorating despite treatment
  • Referring the patient to a specialist when the diagnosis is not clear



Misdiagnosis errors in primary are derived from studies of malpractice claims or self-report surveys, therefore, medical malpractice coverage is vital.  CNA provides medical malpractice insurance to healthcare facilities and practitioners except for physicians, as all licensed Canadian physicians are members of the Canadian Medical Protective Association (CMPA), which provides medico-legal assistance to physicians including legal defence. Need more information about managing your healthcare business risk? Contact us today. 


[1]Singh H, Meyer AND, Thomas EJ. (2014.) The frequency of diagnostic errors in outpatient care: estimations from three large observational studies involving US adult populations. Retrieved at:

[2]CRICO. (2014.)  Annual Benchmarking Report: Malpractice Risks in the Diagnostic Process. Retrieved at:

[3]Op. cit, Institute of Medicine.

[1] Institute of Medicine (IOM). (2015.) Improving Diagnosis in Health Care. Retrieved at:

[2] World Health Organization (WHO). (2016.) Diagnostic Errors: Technical Series on Safer Primary Care. Retrieved at:

[3] Olga Kostopoulou, Brendan C Delaney and Craig W Munro. (2008.) Diagnostic difficulty and error in primary care—a systematic review. Retrieved at:

[4] Ibid.

[5] Canadian Institute for Health Information (CIHI). (2016.) Measuring Patient Harm in Canadian Hospitals. Retrieved at:

[6] Ibid.

[7] Ibid.

[9]CRICO. (2014.)  Annual Benchmarking Report: Malpractice Risks in the Diagnostic Process. Retrieved at:

[10]Op. cit, Institute of Medicine.

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Ruth L Stewart, BA, RN, MHA, CHE
Senior Risk Control Consultant, Healthcare

Ruth Stewart is the Senior Risk Control Consultant, Healthcare for CNA Canada. Ruth brings to her role a background in clinical nursing which includes experience in surgical, intensive care and trauma nursing as well as management of risk in the not-for-profit sector. She left the healthcare sector to work with an international broker using her clinical and operational knowledge to assist acute care and long term care insureds better manage their risks. Ruth works directly with insureds to manage operational risk, and develops publications, tools and other resources to help insureds manage risk. Ruth collaborates with a team of seasoned Healthcare Risk Control/Risk and Governance professionals in the US and UK to provide a comprehensive range of risk services to CNA’s insureds.

Ruth received her nursing training from George Brown College, and her Master in Health Administration from the University of Ottawa. She is a member of the College of Nurses of Ontario (CNO), and a certified member (CHE) of the Canadian College of Health Leaders (CCHL).