579. Variability in QuantiFeron Gold In-Tube Mitogen Tube Performance Necessitating Quality Control Improvement
Session: Poster Abstract Session: Mycobacterial Diagnostics
Friday, October 21, 2011
Room: Poster Hall B1
  • Guerrera_Pirrotta_TB_Poster X (3).pdf (759.1 kB)
  • Background: The Palo Alto Veterans Administration Hospital had run over 6,000 QuantiFeron-TB Gold In-Tube (QFT-GIT) (Cellestis) tests for the detection of latent tuberculosis infection when, without deviating from any procedure in the assay, our facility observed a radical increase in Indeterminate results from 1% to 14.7% during a 10 week period in 2011. The assay’s mitogen tubes are coated with a peptide cocktail to stimulate cells in heparinized whole blood, and it is low mitogen tube levels that cause Indeterminate test results.

    Methods: In order to resolve this inconsistency, we reviewed every procedure variable including (QFT-GIT) blood collection tubes. We identified that all of our Indeterminate results had come from the same lot of mitogen tubes.  We parallel tested this lot of freight-shipped tubes against air-shipped tubes from a different lot on 10 patients with known results.

    Results:  In parallel check, we observed great variation in the level of response between two mitogen tube lots with the same blood samples. Four out of ten of the parallel samples showed variability >40% between the mitogen tube results. After determining that this particular lot of mitogen tubes was performing erratically, the lot’s transportation route was traced and it was found to have passed through the Panama Canal, on deck, during July 2010.  The manufacturer (Greiner) lists the upper temperature limit for the tube’s transport as 25 degrees C. The shipping containers were not temperature-controlled.

    Conclusion: It is probable that this lot of tubes were heat-damaged during transportation. These unique peptide coated tubes are an integral part of the assay and act similarly to the reagent components of the testing kit. Therefore, the QuantiFeron-GIT peptide-coated tubes should be included in a regulated quality assurance program and parallel checks between tubes lots should be performed in accordance with the College of American Pathologists (CAP) regulation IMM.33150.

    Subject Category: D. Diagnostic microbiology

    Virginia Pirrotta, MS, MLS1, Lorraine Guerrera, MLS, SI1, Grace Cheung, MLS1 and Wendy Thanassi, MA, MD2,3, (1)Immunology, Palo Alto Veterans Administration Hospital, Palo Alto, CA, (2)Medicine, Palo Alto Veterans Administration Hospital, Palo Alto , CA, (3)Emergency Medicine, Stanford Hospital and Medical Center, Palo Alto, CA


    V. Pirrotta, None

    L. Guerrera, None

    G. Cheung, None

    W. Thanassi, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.