Genetic Concerns in Public Health (PHELO)

Introduction

Genetic concerns in the context of Population Health, Ethical, Legal, and Organizational (PHELO) aspects of medicine constitute a high-yield area for the MCCQE1. As a Canadian medical graduate, you must navigate not only the clinical indications for genetic testing but also the complex ethical frameworks, legal statutes (such as the Genetic Non-Discrimination Act), and the public health principles governing screening programs.

This guide aligns with the CanMEDS framework, specifically highlighting the roles of Health Advocate (identifying at-risk populations) and Communicator (counseling patients on sensitive genetic data).

Principles of Genetic Screening

For the MCCQE1, understanding the difference between screening and diagnostic testing is fundamental. Public health initiatives rely on screening to identify individuals at higher risk who benefit from further investigation.

Wilson and Jungner Criteria

Any population-based genetic screening program in Canada (e.g., Newborn Screening) must adhere to classic public health criteria:

1. The condition should be an important health problem.
2. There should be an accepted treatment for patients with recognized disease.
3. Facilities for diagnosis and treatment should be available.
4. There should be a recognizable latent or early symptomatic stage.
5. There should be a suitable test or examination.
6. The test should be acceptable to the population.
7. The natural history of the condition should be adequately understood.
8. There should be an agreed policy on whom to treat as patients.
9. The cost of case-finding should be economically balanced in relation to possible expenditure on medical care as a whole.
10. Case-finding should be a continuing process and not a “once and for all” project.

Comparison: Screening vs. Diagnostic Testing

Canadian Genetic Guidelines & Clinical Context

1. Prenatal Screening

The Society of Obstetricians and Gynaecologists of Canada (SOGC) guidelines are the gold standard for MCCQE1 preparation.

• Universal Offer: All pregnant women, regardless of age, should be offered prenatal screening for aneuploidy (Trisomy 13, 18, 21).
• Age Factor: While risk increases with maternal age, age alone is no longer used as the sole criterion for invasive testing.

2. Newborn Screening (NBS)

In Canada, NBS is a provincial responsibility, leading to slight variations in the panel of diseases screened. However, core conditions are consistent.

Commonly Screened Conditions:

• Metabolic: Phenylketonuria (PKU), MCAD deficiency, Galactosemia.
• Endocrine: Congenital Hypothyroidism (CH), Congenital Adrenal Hyperplasia (CAH).
• Hematologic: Sickle Cell Disease.
• Other: Cystic Fibrosis (using IRT), Severe Combined Immunodeficiency (SCID).

3. Hereditary Cancer Syndromes

Recognizing “Red Flags” for referral to medical genetics is a key competency.

Referral Indications:

• Cancer diagnosed at a young age (e.g., breast cancer <50 years).
• Multiple primary cancers in one individual.
• Cancer in paired organs (e.g., bilateral breast or renal cancer).
• Multigenerational pattern of inheritance.
• Rare tumors (e.g., male breast cancer, ovarian cancer).

Ethical and Legal Frameworks in Canada

This section is critical for the PHELO component of the MCCQE1.

The Genetic Non-Discrimination Act (GNDA)

Passed in 2017, this Canadian law protects individuals from genetic discrimination.

Duty to Warn vs. Confidentiality

Canadian privacy laws (e.g., PHIPA, PIPEDA) emphasize patient confidentiality. However, genetic information is familial by nature.

• General Rule: Maintain confidentiality.
• The Conflict: A patient refuses to tell family members about a serious, treatable genetic condition.
• Canadian Approach:
  1. Maximize efforts to persuade the patient to disclose.
  2. Offer to assist in disclosure (e.g., family letter).
  3. Breaching confidentiality to warn at-risk relatives is a last resort and legally complex. It is generally only considered if there is a high risk of serious bodily harm or death that is preventable. Always consult CMPA or legal counsel in exam scenarios before choosing “breach confidentiality” as an answer.

Genetic Counseling Process

For the MCCQE1, you are not expected to be a geneticist, but you must know how to facilitate the process.

Key Points to Remember for MCCQE1

• Consent: Genetic testing requires informed consent, specifically addressing the implications for family members and potential incidental findings.
• Consanguinity: Increases the risk of autosomal recessive conditions.
• Founder Effects: Be aware of specific Canadian populations with higher carrier rates (e.g., Tay-Sachs in Ashkenazi Jewish populations; Tyrosinemia type 1 in Saguenay-Lac-Saint-Jean region of Quebec).
• Abbreviations:

  NIPT  = Non-Invasive Prenatal Testing
  CVS   = Chorionic Villus Sampling
  PKU   = Phenylketonuria
  BRCA  = BReast CAncer gene
  HNPCC = Hereditary Non-Polyposis Colorectal Cancer (Lynch Syndrome)

Sample Question

Clinical Scenario

A 32-year-old woman, G1P0, presents to your office at 10 weeks gestation for her first prenatal visit. She has no significant past medical history. Her partner is 34 years old and healthy. She expresses concern about the risk of Down syndrome because her friend recently had a baby with the condition. She asks if she qualifies for screening given that she is “under 35.”

Question

Which of the following is the most appropriate response regarding prenatal screening guidelines in Canada?

Options

• A. Screening is only covered by provincial health plans for women over the age of 35.
• B. She should be offered invasive testing with amniocentesis immediately to provide a definitive diagnosis.
• C. All pregnant women, regardless of age, should be offered prenatal screening for fetal aneuploidy.
• D. Since she is young and low risk, an anatomy ultrasound at 18 weeks is sufficient screening.
• E. Screening is unnecessary because she has no family history of chromosomal abnormalities.

Explanation

The correct answer is:

• C. All pregnant women, regardless of age, should be offered prenatal screening for fetal aneuploidy.

Detailed Breakdown:

• Option C is correct: According to SOGC guidelines, all pregnant women, regardless of age, should be offered the option of prenatal screening for the most common fetal aneuploidies (Trisomy 21, 18, 13). While the risk of aneuploidy increases with maternal age, a significant number of children with Down syndrome are born to women under 35 because this demographic has the highest birth rate.
• Option A is incorrect: This is an outdated practice. Age >35 is a risk factor, but it is not the sole criterion for offering screening. Provincial funding models have shifted to offer screening (FTS or biochemical) to all women.
• Option B is incorrect: Invasive testing (Amniocentesis or CVS) carries a risk of pregnancy loss. It is a diagnostic test, not a screening test, and is generally reserved for women with a high-risk screening result or specific genetic history. It is not the first-line offer for a low-risk asymptomatic woman.
• Option D is incorrect: While the 18-22 week anatomy scan can detect “soft markers” for aneuploidy, it has lower sensitivity than combined first-trimester screening or NIPT. Relying solely on the second-trimester ultrasound is not the standard of care for aneuploidy screening.
• Option E is incorrect: Most cases of Trisomy 21 are sporadic (due to non-disjunction) and not familial. Lack of family history does not eliminate the risk.

Canadian Guidelines

• SOGC Clinical Practice Guideline No. 348: Joint SOGC-CCMG Guideline: Update on Prenatal Screening for Fetal Aneuploidy, Fetal Anomalies, and Adverse Pregnancy Outcomes (2017/Updated 2022).
• CCMG (Canadian College of Medical Geneticists): Position statements on direct-to-consumer testing and genetic non-discrimination.
• Government of Canada: Genetic Non-Discrimination Act (S.C. 2017, c. 3).

References

1. Audibert, F., De Bie, I., Adamo, L., et al. (2017). Joint SOGC-CCMG Guideline: Update on Prenatal Screening for Fetal Aneuploidy, Fetal Anomalies, and Adverse Pregnancy Outcomes. Journal of Obstetrics and Gynaecology Canada, 39(9), 805-817. Link 
2. Government of Canada. (2017). Genetic Non-Discrimination Act. Available at: https://laws-lois.justice.gc.ca/eng/acts/G-2.5/index.html 
3. Public Health Agency of Canada. (2018). Newborn Screening in Canada.
4. Medical Council of Canada. (n.d.). MCCQE Part I Objectives: Population Health. Available at: https://mcc.ca/