Snapshot of Quantiferon TB gold testing in Northern Mexico

QuantiFERON TB-gold conversion rate among psoriasis patients under biologics: a 9-year retrospective study

BACKGROUND

Tuberculosis (TB) screening is mandatory for psoriasis biologic treatment. However, evidences regarding TB screening results during biologic treatment are conflicting.

OBJECTIVES

The aim of this study is to evaluate the rate of QuantiFERON TB Gold test (QFT) conversion in psoriasis patients during biologics over time.

METHODS

A 9-year single center retrospective study was performed in order to evaluate the rate of QFT conversion in patients affected by moderate-to-severe plaque psoriasis under available biological therapies (anti-TNF-α, IL-12/23, IL-17). For each patient, demographic data, age, gender, comorbidities, previous psoriasis therapy, as well as ongoing treatment type were registered. Five-hundred twenty-six patients (61.2% male, with a mean age of 52.6 ± 13.9 years) treated with biologics were enrolled.

RESULTS

QFT conversion occurred in 6.5% of patients over a mean treatment duration of 3.2 years. On average, QFT conversion occurred after 34.05 months of treatment. Anti-TNF-α drugs, and among them, adalimumab above all (35.5% of all cases), were the most commonly involved treatment during QFT conversion, followed by anti-IL-12/23 (17.6%) and anti-IL-17 (14.7%). However, differences among biologics class or single biologics (adalimumab, etanercept, infliximab, golimumab, certolizumab, ustekinumab, ixekizumab, secukinumab) did not approach statistical significance.

CONCLUSIONS

Annual TB screening is important in psoriasis patients under biologic treatment in order to avoid possible latent TB infection reactivation. Indeed, our data showed that even in a low TB prevalence country like Italy, QFT may convert over time in psoriasis patients under biologics in 6.5% of the cases.

Detection of latent tuberculosis infection among migrant farmworkers along the US-Mexico border

Background

Migrant farmworkers are among the highest-risk populations for latent TB infection (LTBI) in the United States with numerous barriers to healthcare access and increased vulnerability to infectious diseases. LTBI is usually diagnosed on the border using the tuberculin skin test (TST). QuantiFERON-TB Gold In-Tube (QFT-GIT) also measures immune response against specific Mycobacterium tuberculosis antigens. The objective of this study is to assess the comparability of TST and QFT-GIT to detect LTBI among migrant farmworkers on the border, as well as to examine the effects of various demographic and clinical factors on test positivity.

Methods

Participants were recruited using mobile clinics on the San Luis US-Mexico border and tested with QFT-GIT and TST. Demographic profiles and clinical histories were collected. Kappa coefficients assessed agreement between TST and QFT-GIT using various assay cutoffs. Logistic regression examined factors associated with positive TST or QFT-GIT results.

Results

Of 109 participants, 59 of 108 (55 %) were either TST (24/71, 34 %) or QFT-GIT (52/106, 50 %) positive. Concordance between TST and QFT-GIT was fair (71 % agreement, ĸ = 0.38, 95 % CI: 0.15, 0.61). Factors associated with LTBI positivity included smoking (OR = 1.26, 95 % CI–1.01–1.58) and diabetes/high blood sugar (OR = 0.70, 95 % CI = 0.51–0.98).

Discussion

Test concordance between the two tests was fair, with numerous discordant results observed. Greater proportion of positives detected using QFT-GIT may help avoid LTBI under-diagnosis. Assessment of LTBI status on the border provides evidence whether QFT-GIT should replace the TST in routine practice, as well as identifies risk factors for LTBI among migrant populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1959-3) contains supplementary material, which is available to authorized users.

Assessing the Prevalence of Latent Tuberculosis among Health Care Providers in Zagazig City, Egypt Using Tuberculin Skin Test and QuantiFERON-TB Gold In-Tube Test

AIM

Early detection of latent tuberculosis infection (LTBI) will prevent development of active TB among health care providers. The aim of the study was to assess the prevalence of LTBI among health care providers and compare the QuantiFERON-TB Gold In-Tube Test (QFT-GIT) and Tuberculin skin test in efforts to detect LTBI and to investigate possible associated risk factors of infection.

METHODS

A cross sectional study was carried out during the period of 6 months in the Chest Hospital in Zagazig city and the Nephrology Unit at Zagazig University Hospitals in 132 randomly selected health care providers who were examined for LTBI by QFT-GIT and Tuberculin skin test and for the associated risk factors as well.

RESULTS

The prevalence of LTBI identified by QFT-GIT and by Tuberculin skin test was 28.8% and 59.1%, respectively. Poor agreement was observed between the two tests (kappa=0.10). Working more than 10 years, being nurse, diabetic and smoker were risk factors significantly associated with LTBI (p<0.05).

CONCLUSIONS

QFT-GIT is considered a useful tool in detecting LTBI cases, especially in a country where BCG vaccination is a national policy (as in Egypt). Duration of work, profession, diabetes and smoking are the risk factors for LTBI. Active surveillance and infection control measures are recommended to reduce the risk of LTBI.

Interferon Gamma-Based Detection of Latent Tuberculosis Infection in the Border States of Nuevo Leon and Tamaulipas, Mexico

Nearly one-third of the world’s population is infected with latent tuberculosis (LTBI). Tuberculosis (TB) rates in the border states are higher than national rates in both the US and Mexico, with the border accounting for 30% of total registered TB cases in both countries. However, LTBI rates in the general population in Mexican border states are unknown. In this region, LTBI is diagnosed using the tuberculin skin test (TST). New methods of detection more specific than TST have been developed, although there is currently no gold standard for LTBI detection. Our objective is to demonstrate utility of the Quantiferon TB gold In-Tube (QFT-GIT) test compared with the TST to detect LTBI among border populations. This is an observational, cross-sectional study carried out in border areas of the states of Nuevo Leon and Tamaulipas, Mexico. Participants (n = 210) provided a TST and blood sample for the QFT-GIT. Kappa coefficients assessed the agreement between TST and QFT-GIT. Participant characteristics were compared using Fisher exact tests. Thirty-eight percent of participants were diagnosed with LTBI by QFT-GIT. The proportion of LTBI detected using QFT-GIT was almost double [38% (79/210)] that found by TST [19% (39/210)] (P < 0.001). Concordance between TST and QFT-GIT was low (kappa = 0.37). We recommend further studies utilizing the QFT-GIT test to detect LTBI among border populations.

Tuberculin skin test versus interferon-gamma release assays for the diagnosis of tuberculosis infection

OBJECTIVE

Accurate detection of latent tuberculosis infection (LTBI) is becoming increasingly important due to the increasing use of immunosuppressive medications and the human immunodeficiency epidemic, which have increased the risk for reactivation to active tuberculosis (TB) infection. LTBI is detected by tuberculin skin test (TST) and interferon-gamma release assays (IGRAs). The latter include T-SPOT(®).TB (Oxford Immunotec) and QuantiFERON(®)-TB Gold In-Tube (QFT-GIT; Cellestis). We examined the value of TST versus IGRAs in the diagnosis of TB infection by meta-analysis based on data derived from a systematic literature review.

METHODS

PubMed was searched for articles in English published between January 2010 and July 2012 in which TST and IGRA were performed simultaneously in individuals with and without active TB infection. A random effect model meta-analysis was performed to determine pooled sensitivity and specificity values for TST, T-SPOT.TB, and QFT-GIT. Owing to the absence of a gold standard for the diagnosis of LTBI, active TB infection was used as a surrogate for LTBI.

RESULTS

Nineteen studies were included. T-SPOT.TB was significantly more sensitive [90% (95% confidence interval: 85-95) versus 64% (46-81)] than TST. The specificity of T-SPOT.TB was higher than the specificity of TST, but there was overlap between confidence intervals [77% (68-85) versus 57% (41-72)]. QFT-GIT seemed to be more sensitive than TST [75% (61-86) versus 64% (48-78)] but similarly specific [71% (62-86) versus 70% (57-81)].

CONCLUSIONS

IGRAs, especially T-SPOT.TB, are more effective at detecting TB infection than TST. Despite their higher cost, they have added value and can be requested in addition to TST.

Two-step tuberculin skin testing in school-going adolescents with initial 0-4 millimeter responses in a high tuberculosis prevalence setting in South India

Background

The utility of two-step tuberculin skin testing among adolescents in high tuberculosis prevalence settings is not well established.

Objectives

To determine the proportion and determinants of a 0-4 mm response to an initial standard tuberculin skin test (TST) and evaluating 'boosting' with repeat testing.

Methods

Adolescents between 11 and 18 years attending schools/colleges underwent a TST; those with a response of between 0–4 mm had a repeat TST 1-4 weeks later.

Results

Initial TST was done for 6608/6643 participants; 1257 (19%) developed a 0-4 mm response to the initial TST. Younger age and under-nutrition were more likely to be associated with a 0-4 mm response, while the presence of BCG (Bacillus Calmette Guerin) scar and higher socio-economic class were less likely to be associated with a 0-4 mm response. On repeat testing boosting was seen in 13.2% (145/1098; ≥ 6 mm over the initial test) while 4.3% showed boosting using a more conservative cutoff of a repeat TST ≥ 10 mm with an increment of at least 6 mm (47/1098). History of exposure to a tuberculosis (TB) case was associated with enhanced response.

Conclusion

The proportion of adolescents who demonstrated boosting on two-step TST testing in our study was relatively low. As a result repeat testing did not greatly alter the prevalence of TST positivity. However, the two-step TST helps identify individuals who can potentially boost their immune response to a second test, and thus, prevents them from being misclassified as those with newly acquired infection, or tuberculin converters. While two-step tuberculin skin testing may have a limited role in population- level TST surveys, it may be useful where serial tuberculin testing needs to be performed to distinguish those who show an enhanced response or boosters from those who indeed have a new infection, or converters.

Performance of tuberculin skin test compared to QFT-IT to detect latent TB among high-risk contacts in Mexico

BACKGROUND AND AIMS

We undertook this study to compare the performance of tuberculin skin test (TST) and QuantiFERON-TB-Gold In-tube assay (QFT-IT) to identify latent TB infection (LTBI) among close contacts of pulmonary TB cases.

METHODS

A cross-sectional study was conducted in north central Mexico. Thirty nine TB index cases diagnosed between 2008 and 2010 and 123 corresponding close contacts were interviewed regarding their exposure time to the index case prior to TB diagnosis and relevant sociodemographic factors. TST (induration ≥5 and ≥10 mm) and QFT-IT (≥0.35 IU/mL) were tested to determine LTBI status. Kappa coefficients were used to assess the agreement between TST and QFT-IT. Multivariate logistic regression modeling using TST and QFT-IT as dependent variables, and cumulative exposure time and sociodemographic variables associated with LTBI were used as independent variables.

RESULTS

LTBI prevalence in adult contacts was 53.6 and 34.1% when TST cut-offs were set at ≥5 mm and ≥10, respectively, and 41.4% according to QFT-IT. Agreement between TST and QFT-IT was 73.1 and 74.8%, and kappa coefficients 0.47 and 0.46, for TST ≥5 and ≥10 mm, respectively, although these were higher when data were stratified by cumulative exposure, reaching 84.9% and 0.70 for TST ≥5 mm if exposure was ≥500 h/month. None of the predictive variables analyzed for LTBI using multivariate regression was significantly associated.

CONCLUSIONS

TST ≥5 mm appears to be a useful test to identify LTBI among closely exposed contacts in this geographic setting.

Dynamic QuantiFERON Response in Psoriasis Patients Taking Long-Term Biologic Therapy

Introduction

The risk of active tuberculosis is increased in psoriasis patients receiving biologic drug therapy. The QuantiFERON-TB Gold In-Tube assay (QFT) is used for latent tuberculosis screening in these patients. This study presents a retrospective analysis on repeated QFT assays, investigating the influence of biologic drugs and isoniazid therapy on the outcome of the assay.

Methods

Serial QFTs of 58 psoriasis patients, who received biologic drug therapy, were evaluated at baseline and after 12 months of treatment. Patients were retrospectively divided in four groups according to QFT results at baseline and at follow-up: patients having a QFT reversion (from positive to negative results); patients with a conversion (from negative to positive); patients confirming the baseline results, either positive or negative.

Results

At the end of the 12-months period, 11.1% of patients with a negative QFT result at baseline presented a conversion, showing low interferon (IFN)-gamma values, whereas 6.9% of positive patients presented a QFT reversion. When the test was repeated after 2–3 months without isoniazid chemoprophylaxis, patients with QFT conversion showed negative results. No patient developed active tuberculosis.

Conclusions

In patients undergoing biologic therapy, a positive QFT assay needs to be further confirmed, as false-positive results may occur after long-term therapy. Repeating QFT tests in patients with low IFN-gamma values could reduce the incidence of false-positive latent tuberculosis infection diagnosis, thus preventing unnecessary tuberculosis chemoprophylaxis. In conclusion, a dynamic QFT response is possible in psoriasis patients undergoing biologic therapy.