Pollock Nira R, Campos-Neto Antonio, Kashino Suely, Napolitano Danielle, Behar Samuel M, Shin Daniel, Sloutsky Alex, Joshi Swati, Guillet Jasmine, Wong Michael, Nardell Edward
Department of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02115, USA.
Infect Control Hosp Epidemiol. 2008 Sep;29(9):878-86. doi: 10.1086/590262.
In late 2006, our hospital implemented use of the QuantiFERON-TB Gold (QFT-G) assay, a whole-blood interferon-gamma release assay, for detection of tuberculosis infection. All newly hired healthcare workers (HCWs) with positive Mantoux tuberculin skin test (TST) results were routinely tested with the QFT-G assay, to take advantage of its higher specificity. We then undertook a quality assurance review to evaluate the QFT-G test results in HCWs with multiple risk factors for latent tuberculosis infection (LTBI).
The clinical records for TST-positive HCWs tested with the QFT-G assay were reviewed. HCWs with 2 or more risk factors commonly associated with LTBI were classified as "increased risk" (IR). IR HCWs who had negative QFT-G test results underwent repeat QFT-G testing and were offered testing with a different interferon-gamma release assay (T-SPOT.TB) and with extended T cell stimulation assays.
Of 143 TST-positive HCWs tested with the QFT-G assay, 26 (18%) had positive results, 115 (81%) had negative results, and 2 (1%) had indeterminate results. Of 82 IR HCWs, 23 (28%) had positive QFT-G test results, and 57 (70%) had negative results. Of the 57 IR HCWs with negative results, 43 underwent repeat QFT-G testing: 41 had negative results again, and 2 had positive results. These 43 HCWs were also offered additional testing with the T-SPOT.TB diagnostic, and 36 consented: 31/36 tested negative, and 5/36 tested positive. Extended assays using the antigens ESAT-6 and CFP-10 confirmed the positive results detected by the overnight assays and yielded positive results for an additional 7/36 (19%) of individuals; strikingly, all 36 HCWs had strongly positive test results with assays using purified protein derivative.
The extreme discordance between the results of our clinical diagnostic algorithm and the results of QFT-G testing raises concern about the sensitivity of the QFT-G assay for detection of LTBI in our HCWs. Results of extended stimulation assays suggest that many of our IR HCWs have indeed been sensitized to Mycobacterium tuberculosis. It is possible that the QFT-G assay identifies those at higher reactivation risk rather than all previously infected, but, in the absence of long-term follow-up data, we should interpret negative QFT-G results with some caution.
2006年末，我院开始使用全血干扰素-γ释放试验QuantiFERON-TB Gold（QFT-G）检测结核病感染情况。所有新入职的结核菌素皮肤试验（TST）结果呈阳性的医护人员（HCW）均常规接受QFT-G检测，以利用其较高的特异性。随后，我们进行了质量保证评估，以评价QFT-G检测在具有多种潜伏性结核感染（LTBI）风险因素的医护人员中的检测结果。
回顾了接受QFT-G检测的TST阳性医护人员的临床记录。具有2种或更多种通常与LTBI相关的风险因素的医护人员被归类为“高风险”（IR）。QFT-G检测结果为阴性的IR医护人员接受了重复QFT-G检测，并接受了另一种干扰素-γ释放试验（T-SPOT.TB）和延长T细胞刺激试验的检测。
在143名接受QFT-G检测的TST阳性医护人员中，26名（18%）结果为阳性，115名（81%）结果为阴性，2名（1%）结果不确定。在82名IR医护人员中，23名（28%）QFT-G检测结果为阳性，57名（70%）结果为阴性。在57名结果为阴性的IR医护人员中，43名接受了重复QFT-G检测：41名再次检测结果为阴性，2名结果为阳性。这43名医护人员还接受了T-SPOT.TB诊断的额外检测，36名同意：36名中有31名检测为阴性，5名检测为阳性。使用抗原ESAT-6和CFP-10的延长试验证实了过夜试验检测到的阳性结果，并使另外7/36（19%）的个体检测结果呈阳性；引人注目的是，所有36名医护人员使用纯化蛋白衍生物进行的试验检测结果均为强阳性。
我们的临床诊断算法结果与QFT-G检测结果之间的极度不一致引发了对QFT-G检测在我院医护人员中检测LTBI敏感性的担忧。延长刺激试验的结果表明，我们的许多IR医护人员确实对结核分枝杆菌敏感。有可能QFT-G检测识别出再激活风险较高的人，而不是所有既往感染者，但在缺乏长期随访数据的情况下，我们对QFT-G阴性结果的解释应谨慎。
