573. Predicting Indeterminate QuantiFERON-TB Gold (QFT) Test Results in an HIV Infected Population
Session: Poster Abstract Session: Mycobacterial Diagnostics
Friday, October 21, 2011
Room: Poster Hall B1
Handouts
  • IDSA_QFT_17Oct11 Final[1].pdf (743.3 kB)
  • Predicting Indeterminate QuantiFERON-TB Gold (QFT) Test Results in an HIV Infected Population

    Background: The QuantiFERON-TB Gold (QFT) test was approved by the U.S. Food and Drug Administration in 2005 to aid in diagnosing and screening Mycobacterium tuberculosis (TB) infection.  HIV infection is a known risk factor for reactivation of TB. In HIV individuals, QFT has been shown to be more sensitive than Tuberculin Skin Test; however, indeterminate results are known to be more prevalent in this patient population, especially in those who have lower CD4 counts. The purpose of this study is to identify factors that promote QFT indeterminate results in an urban HIV Clinic. Methods: Medical records and laboratory data of all HIV+ patients at the Erie County Medical Center Immunodeficiency Clinic in Buffalo, NY were reviewed for both QFT and previous Purified Protein Derivative (PPD) testing. CD4 count, viral load, and anti-retrovirals taken at the time of blood draw for QFT were also recorded. Results: A total of 1,422 QFT tests were done in 1,023 patients (Median age: 49; Median CD4: 524; Median VL: <48 copies; 331 F/ 692 M; 552 W/ 434 B/ 37 others) between 10/1/09 – 4/1/11. A total of 60 (4.3%) positive (P), 51 (3.6%) indeterminate (I) and 1310 (92.1%) negative (N) QFT results were identified.  The prevalence of P-QFT is calculated as 5.2% in this HIV cohort whereas the regional incidence of TB is approximately 1.5/100,000/year. Based on logistic regression analysis, a CD4 <100 and a higher HIV viral load were predictive of I-QFT results.   The rate of I-QFT results in HIV+ patients ranged from 1.7% to 37% based on both factors. Conclusion:  The chance of an indeterminate result increased as VL increased with this effect being more predominant in patients with CD4<100.  With controlled HIV viral replication and CD4 > 100, the I-QFT rate may be reduced to less than 2%.  Using QFT in an advanced AIDS patient may not be clinically useful, and may unnecessarily increase health care spending.


    Subject Category: C. Clinical studies of bacterial infections and antibacterials including sexually transmitted diseases and mycobacterial infections (surveys, epidemiology, and clinical trials)

    Chiu-Bin Hsiao, MD, MSBS1, Eva Mok, MD2, Brent Footer, PharmD3, Mark Paul Visitacion, MD4, Laurie Abbatessa, RNP1, Adel Sulaiman, MD1 and Daniel Amsterdam, PhD5, (1)Medicine, University at Buffalo/ Erie County Medical Center, Buffalo, NY, (2)University at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, NY, (3)University at Buffalo, School of Pharmacy , Buffalo, NY, (4)Medicine, University at Buffalo, School of Medicine and Biomedical Sciences, Buffalo, NY, (5)Laboratory Medicine, University at Buffalo/Erie County Medical Center, Buffalo, NY

    Disclosures:

    C. B. Hsiao, None

    E. Mok, None

    B. Footer, None

    M. P. Visitacion, None

    L. Abbatessa, None

    A. Sulaiman, None

    D. Amsterdam, 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.