IGRA testing in patients with immune-mediated inflammatory diseases: which factors influence the results?

Diagnosis of latent tuberculosis infection in patients with immune-mediated inflammatory chronic diseases (IMIDs) can be challenged as diagnostic test reliability could be impaired by immunosuppression. We retrospectively analyzed the Quantiferon Gold-Test in-Tube (QFT-G-IT) results of all patients with IMIDs seen at the Department of Internal Medicine of Son Llàtzer Hospital, Palma de Mallorca (Spain), looking for the factors related to QFT-G-IT indeterminate results. During the study period (2008-2015), 520 patients met the inclusion criteria. Factors associated with indeterminate QFT-G-IT results in a univariate analysis were inflammatory bowel disease, disease activity, lymphopenia, and medium-to-high doses of corticosteroids. In a subsequent multivariate analysis, only lymphopenia (defined as < 1500 cells) was associated with indeterminate QFT-G-IT results. Lymphocyte count was the only factor independently associated with an increased number of indeterminate QFT-G-IT results in patients with different autoimmune diseases. Others factors such as the use of medium-to-high doses of corticosteroids should be considered before testing with QFT-G-IT.

Use of Quantiferon-TB-Gold in Tube(®) test for detecting latent tuberculosis in patients considered as candidates for anti-TNF therapy in routine clinical practice.

BACKGROUND/METHODS: Quantiferon-TB-Gold in Tube(®) test (QFT-G-IT) may have advantages if combined with TST when screening for Latent Tuberculosis Infection (LTBI) prior to initiating anti-TNF therapy in an area of intermediate tuberculosis incidence such as Spain. In a small-scale prospective study, we evaluate the use of QFT-G-IT in combination with the screening recommended in Spain (Tuberculin-Skin Test, TST retest, clinical data, and Chest X-Ray (CXR)) for LTBI in patients considered as candidates for anti-TNFα treatment. RESULTS: From June 2008 to October 2010, 123 patients from a 300-bed hospital in Palma de Mallorca (Spain) were included in the study. The majority of patients were under immunosuppressive therapy. A positive TST and TST booster were found in 22 and 17 patients, respectively. Thus 39 (31.7%) of the 123 patients had a positive TST. QFT-G-IT was positive in 16 patients (13.6%), indeterminate in 4 (3.2%), and negative in 103 (83.7%). One of the two tests was positive and LTBI was diagnosed in 34.1% of patients. The agreement between TST and QFT-G-IT among vaccinated patients was low and not statistically significant (Kappa=0.15) and was almost perfect among non-BCG vaccinated patients (K=0.81). TST positive responses were significantly related to BCG-vaccination (p<0.05) and QFT-G-IT positive response rates were related to older age (p<0.05). CONCLUSION: QFT-G-IT may have advantages when combined with TST in immunosuppressed patients especially in older patients with a negative TST; in BCG vaccinated patients with a positive TST, QFT-G-IT could avoid unnecessary treatments and toxicities related to a false-positive TST result.

[Quantiferon-TB Gold In-Tube test in the diagnosis of pulmonary and extra-pulmonary tuberculosis]. / Valor de QuantiFERON-TB Gold Test in Tube en el diagnóstico de tuberculosis pulmonar y extrapulmonar.

INTRODUCTION: The Interferon-γ in vitro detection tests could be a useful tool in the diagnosis of active tuberculosis compared to Mycobacterium tuberculosis (MTB). METHODS: The QuantiFERON-TB-Gold in Tube (QFG-IT) test was performed on the blood of 118 patients with active tuberculosis and the results compared with the tuberculin test. RESULTS: The QFG-IT test was positive in 94 cases (79.7%), negative in 17 (14.4%) and indeterminate in 7 (5.9%). A negative or indeterminate QFG-IT test was more common in older patients (P=0.017) and in cases with negative smear tests (P=0.041). The kappa agreement between the tuberculin and QFG-IT tests was 74.5% with a kappa value of 0.45 (SE:0.136). Thirteen of the patients studied were infected with HIV and the tuberculin was positive in 5 of the 12 cases (38.5%) in whom it was performed, with the QFG-IT being positive in 9/13 (69.2%). CONCLUSIONS: The QFG-IT test may be a useful complimentary tool to the tuberculin test in the diagnosis of tuberculosis.

Role of QuantiFERON(®)-TB Gold In-Tube in tuberculosis contact investigation: experience in a tuberculosis unit.

BACKGROUND: Interferon-γ release assays (IGRAs) are increasingly used for the diagnosis of latent tuberculosis infection (LTBI). Because of the lack of a gold standard for the diagnosis of LTBI, IGRAs are compared to the tuberculin skin test (TST) and yield conflicting results. We assessed the usefulness of an IGRA test, QuantiFERON(®)-TB Gold In-Tube (QFT-G-IT), for diagnosing LTBI compared with TST in the setting of a contact screening study. METHODS: A prospective comparison between the QFT-G-IT and the TST in TB contact subjects in a low TB burden area was conducted sequentially between January 2006 and December 2012. RESULTS: A moderate concordance between the two tests (κ = 0.44 for TST cut-off of 5 mm and κ = 0.56 for TST cut-off of 15 mm) was found. A better agreement was shown in younger contacts and in non-vaccinated contacts when using a TST of 15 mm. Independent risk factors for a TST(+)/QFT-G-IT(-) discordance were history of BCG vaccination and age between 31 and 59 years. Discordance was also more frequent using a TST cut-off value of 5 mm. QFT-G-IT(+)/TST(-) was infrequent and was found in older contacts. CONCLUSIONS: Based on our data, we cannot recommend the use of QFT-G-IT as the only test to rule out LTBI, especially in older patients.

What is new in listeriosis?

Listeriosis is a disease caused by Listeria monocytogenes (L. monocytogenes). L. monocytogenes is bacteria that usually infects some determined inhabitants, especially high risk patients such as the elderly, immunosuppressed patients and pregnant women. However, it can also affect people who do not have these risk factors. L. monocytogenes is widespread in nature being part of the faecal flora of many mammals and it is a common foodborne source. It is acquired by humans primarily through consumption of contaminated food. Besides, between 1% and 10% of the population is a faecal carrier of L.monocytogenes. Listeriosis may occur sporadically or in outbreaks. Infection causes a spectrum of illness, ranging from febrile gastroenteritis to invasive disease, including bacteraemia, sepsis, and meningoencephalitis. This infection has a low incidence, although it is undeniably increasing, particularly due to the rise of population of over 60 years old or of under 60 years olds with a predisposing condition. The diagnosis is complicated because of its incubation period and the different clinical manifestations. Also listeriosis has a high mortality despite adequate and early treatment. The importance of bacteraemia for L. monocytogenes lies in the infrequency of this bacterium and the high mortality, even with appropriate antibiotic treatment.