How do you screen for TB at 65? A guide to testing for older adults

Over one-quarter of all TB cases in the US are found in adults aged 65 and older. Understanding how do you screen for TB at 65? is crucial, as age-related immune changes and past exposures can impact testing. Health authorities recommend specific, reliable methods for this demographic.

Quick Summary

Screening for tuberculosis in adults over 65 typically involves a blood test, known as an Interferon-Gamma Release Assay (IGRA), due to its higher accuracy in older populations, unlike the less reliable skin test. A positive result warrants further evaluation, which may include a chest x-ray and symptom review to distinguish between latent and active infection.

Key Points

• IGRA Blood Test Preferred: The Interferon-Gamma Release Assay (IGRA) is the recommended TB screening method for most adults over 65 due to its higher accuracy compared to the skin test.

• TST Limitations in Seniors: The traditional TB skin test (TST) can produce less reliable results in older adults due to age-related changes in the immune system.

• BCG Vaccine Not a Factor for IGRA: The IGRA blood test is not affected by prior BCG vaccination, which can cause false-positive TST results.

• Positive Test Requires Follow-Up: A positive result from any TB test indicates infection, but not necessarily active disease. A chest x-ray is needed to determine if the infection is active or latent.

• Risk Factors Are Key: A medical history and risk assessment are crucial for all screening, as conditions like diabetes and residence in congregate settings increase risk.

• Treatment is Available for Latent TB: If diagnosed with latent TB infection, seniors can receive preventative treatment to significantly reduce the risk of it progressing to active disease.

Why Screening is Different for Seniors

As individuals age, their immune system undergoes changes, which can affect how the body responds to diagnostic tests. This makes some methods, like the traditional Tuberculin Skin Test (TST), less reliable for detecting tuberculosis (TB) infection in older adults. Age-related immune decline, or immunosenescence, can impact test accuracy. Seniors also face a higher risk of TB reactivation from past exposures. Risk factors for TB in seniors include residence in long-term care facilities, diabetes, and other co-morbidities.

The Preferred Method: IGRA Blood Tests

The CDC generally recommends an Interferon-Gamma Release Assay (IGRA) blood test for TB screening in most people over 65. IGRA tests are more specific for Mycobacterium tuberculosis and are not affected by the BCG vaccine, which many seniors may have received. FDA-approved IGRAs include QuantiFERON®-TB Gold Plus and T-SPOT®.TB. Key advantages of IGRA include requiring only a single visit for a blood draw and providing objective, lab-generated results, reducing potential for subjective interpretation.

What About the TB Skin Test (TST)?

While the TST (Mantoux test) is still used, its limitations make it less ideal for seniors, particularly those in long-term care. Challenges with TST in older adults include the "boosting phenomenon," which can cause a false-positive result on a second test in individuals with old latent infections, and reduced immune response (immunosenescence) leading to false-negative results.

Screening Process and Follow-Up

The TB screening process for seniors involves a structured approach, especially important in congregate settings with higher transmission risk.

1. Risk Assessment: Evaluation of medical history, symptoms, and risk factors for exposure is the first step.
2. Initial Testing: An IGRA blood test is typically performed. If unavailable, a TST, often a two-step process, may be used.
3. Interpreting Positive Results: A positive test indicates TB bacteria are present but doesn't differentiate between latent TB infection (LTBI) and active TB disease.
4. Further Evaluation: A positive result necessitates a chest x-ray to check for signs of active TB in the lungs. A sputum test might also be needed if the chest x-ray is abnormal or active TB symptoms are present.
5. Diagnosis and Treatment: Seniors with a positive test, but a normal chest x-ray and no symptoms, are diagnosed with LTBI and may be offered preventative treatment.

IGRA vs. TST: A Comparison for Seniors

The IGRA blood test and the Tuberculin Skin Test (TST) differ significantly, particularly in their reliability for seniors. IGRAs, requiring a single blood draw, are not affected by the BCG vaccine and offer more reliable results in older adults compared to the TST, which requires multiple visits, can be affected by the BCG vaccine, and is less reliable due to immunosenescence and the 'boosting' phenomenon. IGRAs provide objective, lab-generated results, whereas TST interpretation is subjective.

Conclusion: Prioritizing Accuracy for Senior Health

Due to the limitations of the skin test in older adults, the IGRA blood test is generally preferred for screening for latent TB infection in seniors. Its accuracy, convenience, and lack of interference from BCG vaccination make it a more reliable option. Understanding the differences between tests is crucial for effective care, especially in high-risk settings. Always consult a healthcare provider for the most appropriate screening method based on individual factors. For detailed information on TB testing, the CDC provides valuable resources: CDC Tuberculosis Information.

Frequently Asked Questions

What is the most accurate TB test for someone over 65?

For most individuals over 65, the Interferon-Gamma Release Assay (IGRA) blood test, such as QuantiFERON-TB Gold Plus, is considered the most accurate method. It is more specific for TB bacteria and is not affected by prior BCG vaccination, unlike the skin test.

Does being over 65 increase my risk of developing TB?

Yes, older adults are at a higher risk of developing active TB disease, often due to the reactivation of a latent infection acquired years ago. Age-related immune system changes (immunosenescence) are a significant contributing factor.

Is a two-step skin test necessary for seniors?

A two-step skin test procedure is often recommended when using a TST for initial screening in seniors to account for the "boosting" phenomenon, which can cause an inaccurate negative result on the first test.

What happens if a senior's TB test is positive?

A positive test, whether an IGRA or TST, indicates the presence of TB bacteria. The next step is a medical evaluation, including a chest x-ray and symptom review, to determine if the infection is latent or active disease.

Are there special considerations for seniors in long-term care facilities?

Yes. Residents in long-term care facilities are often screened upon admission. Guidelines for these settings emphasize accurate baseline testing, often favoring IGRAs over TSTs, and ongoing vigilance for symptoms of active TB.

Why is the skin test less reliable in older adults?

The skin test relies on a strong T-cell response. As people age, immunosenescence can weaken this response, potentially leading to a false-negative test result even if an infection is present.

Do I need to be retested for TB every year after 65?

Annual re-testing is not typically recommended for asymptomatic seniors with a previously documented negative result, unless they have a known exposure or new risk factors. For those in high-risk congregate settings, an annual clinical evaluation for symptoms is often sufficient after baseline testing.