Diel or No Diel

(I really just wanted to use that Title)


The American Association for Clinical Chemistry (AACC) has published a summary of the Diel findings in their June Newsletter


I think we all know now that the Diel meta-analysis is the most important research result driving the progression of QuantiFERON TB Gold into the market. The addition of the imminent release of the CDC Guidelines should give Cellestis the opportunity that it has been waiting for to be able to aggressively market the product.


(Please also read the note below)

June 2010: Volume 36, Number 6 Interferon-g Release Assays Out-Perform Tuberculin Skin Tests in Detecting Active TB A new meta-analysis comparing interferon-g release assays (IGRAs) for detecting active tuberculosis (TB) found that in comparison to the tuberculin skin test (TST), the newest commercial IGRAs are superior for detecting the disease, particularly in developed countries (Chest 2010; 137:952–68). According to the authors, the findings support the primary use of IGRAs, especially in high-risk groups such as immunosuppressed individuals with high potential for TB reactivation. Due to the poor accuracy of TST among patients with TB, two-step screening strategies with TST as a first test and IGRA as a second should be considered for contact tracing. The authors conducted the study in response to a plethora of recent research about IGRAs, which followed an earlier meta-analysis that summarized studies involving a second-generation Quanti-FERON Gold whole blood ELISA test with a variety of ELISpot assays using different cutoffs and preparations. With Food and Drug Administration approval of both the T-Spot.TB ELISpot, and a new QuantiFERON-Gold In-Tube assay incorporating a third RD-11 antigen, TB 7.7, the authors sought to establish performance benchmarks that laboratorians can expect when using the products. From an initial 679 potentially relevant studies, the authors included 124 in their final analysis. Overall, the pooled sensitivity of TST was 70% versus 81% for Quanti-FERON-Gold In-Tube and 88% for T-Spot.TB. Sensitivities for the latter two increased to 84% and 89%, respectively, when results were restricted to developed countries. Pooled specificity was 99% and 86% for the QuantiFERON-Gold In-Tube and T-Spot.TB, respectively. The researchers also found that there was a lower frequency of indeterminate results among individuals tested with QuantiFERON-Gold In-Tube in comparison to T-Spot.TB, regardless of whether the patient was immunocompetent or immunocompromised.

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I should take the time to point out that the editing of this item from the original Diel text has resulted in a slightly changed (and incorrect) meaning in one area.


Compare the text.


Diel:

Considering sensitivity for diagnosing active TB as a surrogate parameter for LTBI, TST- based two step screening strategies (TST first, IGRA second) for contact tracing should be critically reconsidered due to the poor TST accuracy among TB patients.

AACC:

Due to the poor accuracy of TST among patients with TB, two-step screening strategies with TST as a first test and IGRA as a second should be considered for contact tracing.

Quite a significant difference in meaning!