New CDC Guidelines

TB ALERT: New CDC Guidelines for Targeted TB Testing

CDC. MMWR 2010;59(No. RR-5):1-25.

Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection - United States, 2010.

Guideline Highlights

The T-SPOT.TB test may now be used in place of the tuberculin skin test (TST) in all situations in which the CDC recommends tuberculin skin testing.¹

Targeted Testing Specific Recommendations

• “An IGRA is preferred for testing persons who have received BCG (as a vaccine of for cancer therapy).”¹
  
  
•  “An IGRA is preferred for testing persons from groups that historically have low rates of returning to have TSTs read.”¹

Routine Use

“IGRAs may be used in place of (but not in addition to) a TST in all situations in which CDC recommends tuberculin skin testing as an aid in diagnosing M. tuberculosis infection.”¹

Use of a Borderline Category

“Incorporation of a borderline category for the T-Spot as approved by the FDA increases test accuracy by classifying results near the cut point (at which small variations might affect the interpretation) as neither positive or negative.”¹

Reporting of Test Results

“Both the standard qualitative test interpretation and the quantitative assay measurements should be reported together with the criteria used for test interpretation.”¹

Contact Tracings

“An IGRA or a TST may be used without preference to test recent contacts of persons known or suspected to have active tuberculosis with special considerations for follow-up testing.”¹

Healthcare Worker Screening

“An IGRA or a TST may be used without preference for periodic screening of persons who might have  occupational exposure to M. tuberculosis (e.g., surveillance programs for healthcare workers) with special considerations regarding conversions and reversions.” ¹

Considerations for Programs

There are several programmatic considerations identified in the new CDC Guidelines. These include:

1. IGRA results can be available within 24 hours without the need for a second visit

2. IGRAs are not subject to the same biases and errors associated with TST placement and reading

3. The cost of material for an IGRA is higher than for a TST, but the increase in cost may be offset by decreases in the number of people testing positive

4. Use of an IGRA may increase acceptance of treatment for LTBI

¹ CDC. MMWR 2010;59(No. RR-5):1-25.