Should I screen my first-degree relatives, such as my brother and sister, for alpha‑1 antitrypsin deficiency?

Should You Screen Your Siblings for Alpha-1 Antitrypsin Deficiency?

Yes, testing is strongly recommended for your siblings (brother and sister) if you have been diagnosed with alpha-1 antitrypsin deficiency, particularly if you are homozygous (PI*ZZ). 1

Strength of Recommendation Based on Your Genotype

If You Are Homozygous (PI*ZZ)

Type A Recommendation: Testing is recommended for all siblings 1

Why this matters:

• Your siblings have a 25% to 100% chance of also being homozygous (PI*ZZ), depending on your parents' genotypes 1
• The most likely scenario is that both parents are heterozygous carriers (PI*MZ), giving each sibling a 25% chance of severe deficiency
• However, if one or both parents are also PI*ZZ, the risk increases dramatically to 50-100% 1
• This is especially important in northern European populations where prevalence may be higher 1

If You Are Heterozygous (PIMZ or PISZ)

Type B Recommendation: Testing should be discussed and offered 1

Why this matters:

• Each sibling has a 25% chance of being a heterozygote 1
• Even heterozygotes may be at risk for adverse health effects, particularly lung disease when combined with smoking or environmental exposures 1
• The high prevalence of being at least a carrier warrants discussion and offering of testing 1

Critical Benefits of Early Detection in Siblings

Lifestyle modification and prevention:

• Most important: smoking avoidance (including secondhand smoke) is the single most critical intervention 2, 3
• Avoidance of occupational exposures and environmental pollutants 2
• Early detection allows these interventions before lung damage occurs 2, 3

Medical management:

• Enables careful lung function monitoring through serial spirometry 4, 3
• Allows consideration of augmentation therapy while lung function is still preserved 2, 3
• Facilitates appropriate vaccinations and targeted medical care 3

Cascade screening efficiency:

• Family testing of first-degree relatives is currently the most efficient detection technique for AATD 3
• Identifies at-risk individuals who might otherwise remain undiagnosed for years 5, 6

Practical Testing Approach for Your Siblings

The 2025 Canadian Thoracic Society guidelines 7 recommend a modern, precise approach:

1. Initial step: Measure serum AAT level

   • If <23 mmol/L (<1.2 g/L), proceed to genetic testing

2. Definitive diagnosis: DNA sequencing of the SERPINA1 gene

   • This is superior to older phenotyping methods 7
   • Identifies all 300+ genetic variants in a single assay 7
   • Provides precise risk stratification (e.g., distinguishing PIMZ from PISZ, which carry different disease risks) 7

3. Genetic counseling should accompany testing to discuss implications 1, 7

Important Caveats

Potential psychosocial considerations:

• There may be adverse psychological effects from learning about genetic risk 1
• Potential concerns about insurance and employment discrimination 1, 2
• These concerns are generally outweighed by the benefits of early detection and intervention 2

The underdiagnosis problem:

• AATD remains severely underdiagnosed—fewer than 10% of affected individuals in the US have been identified 6
• Patients often see multiple physicians over many years before diagnosis 6
• Your siblings could avoid this diagnostic odyssey through proactive testing 5

Why This Matters for Morbidity and Mortality

Early identification fundamentally changes outcomes:

• Prevents progressive lung destruction through smoking avoidance and environmental modifications 2, 3
• Reduces risk of premature death from emphysema, particularly in homozygotes 1
• Enables disease-modifying therapy (augmentation therapy) when appropriate 3, 8
• Identifies liver disease risk early, allowing monitoring and timely intervention 9

The case report of a 68-year-old patient who died from complications after years of misdiagnosed "COPD" that was actually unrecognized AATD illustrates the tragic consequences of delayed diagnosis 5. Your siblings should not face this same risk when testing is readily available.

Bottom line: Offer testing to your siblings now, with appropriate genetic counseling, regardless of whether they have symptoms. The evidence strongly supports this approach for preventing disease and improving long-term outcomes.