When Is an IGRA Conversion False Positive?

Among hospital employees who underwent serial interferon-γ release assay testing, converters with interferon levels close to the cutoff value often tested negative months later.

In high-income western countries, interferon-γ release assays (IGRAs) have largely replaced the classic tuberculin skin test for diagnosing latent tuberculosis (TB). They appear promising for serial testing, but determining the clinical significance of conversions with low-positive IGRA results has been problematic.

Researchers recently published their experience with repeat testing of healthcare workers (HCWs) at the Cleveland Clinic. From 2007 through 2010, 52 of 1857 HCWs (2.8%) with negative pre-employment IGRA screening results subsequently had positive results on annual testing. Repeat IGRA values were ≤1 IU/mL in 71% of the converters and 0.35 to 0.5 IU/mL — near the cutoff — in 37%; the median value was 0.63 IU/mL. Forty-four percent…

Reviewing Author

Thomas Glück, MD

Disclosures

Editorial BoardsConsilium Infectiorum by InfectoPharm, Infection

Thomas Glück, MD

Disclosures

Editorial BoardsConsilium Infectiorum by InfectoPharm, Infection

When Is an IGRA Conversion False Positive?

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Reviewing Author