Interferon-γ release assay as a sensitive diagnostic tool of latent tuberculosis infection in patients with HIV: a cross-sectional study

Serum cytokine biosignatures for identification of tuberculosis among HIV-positive inpatients

BACKGROUND

Serum cytokines correlate with tuberculosis (TB) progression and are predictors of TB recurrence in people living with HIV. We investigated whether serum cytokine biosignatures could diagnose TB among HIV-positive inpatients.

METHODS

We recruited HIV-positive inpatients with symptoms of TB and measured serum levels of inflammation biomarkers including IL-2, IL-4, IL-6, IL-10, tumour necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ). We then built and tested our TB prediction model.

RESULTS

236 HIV-positive inpatients were enrolled in the first cohort and all the inflammation biomarkers were significantly higher in participants with microbiologically confirmed TB than those without TB. A binary support vector machine (SVM) model was built, incorporating the data of four biomarkers (IL-6, IL-10, TNF-α and IFN-γ). Efficacy of the SVM model was assessed in training (n=189) and validation (n=47) sets with area under the curve (AUC) of 0.92 (95% CI 0.88 to 0.96) and 0.85 (95% CI 0.72 to 0.97), respectively. In an independent test set (n=110), the SVM model yielded an AUC of 0.85 (95% CI 0.76 to 0.94) with 78% (95% CI 68% to 87%) specificity and 85% (95% CI 66% to 96%) sensitivity. Moreover, the SVM model outperformed interferon-gamma release assay (IGRA) among advanced HIV-positive inpatients irrespective of CD4+ T-cell counts, which may be an alternative approach for identifying Mycobacterium tuberculosis infection among HIV-positive inpatients with negative IGRA.

CONCLUSIONS

The four-cytokine biosignature model successfully identified TB among HIV-positive inpatients. This diagnostic model may be an alternative approach to diagnose TB in advanced HIV-positive inpatients with low CD4+ T-cell counts.

Understanding the Decline of Incident, Active Tuberculosis in People With Human Immunodeficiency Virus in Switzerland

BACKGROUND

People with human immunodeficiency virus type 1 (HIV-1) (PWH) are frequently coinfected with Mycobacterium tuberculosis (MTB) and at risk for progressing from asymptomatic latent TB infection (LTBI) to active tuberculosis (TB). LTBI testing and preventive treatment (TB specific prevention) are recommended, but its efficacy in low transmission settings is unclear.

METHODS

We included PWH enrolled from 1988 to 2022 in the Swiss HIV Cohort study (SHCS). The outcome, incident TB, was defined as TB ≥6 months after SHCS inclusion. We assessed its risk factors using a time-updated hazard regression, modeled the potential impact of modifiable factors on TB incidence, performed mediation analysis to assess underlying causes of time trends, and evaluated preventive measures.

RESULTS

In 21 528 PWH, LTBI prevalence declined from 15.1% in 2001% to 4.6% in 2021. Incident TB declined from 90.8 cases/1000 person-years in 1989 to 0.1 in 2021. A positive LTBI test showed a higher risk for incident TB (hazard ratio [HR] 9.8, 5.8-16.5) but only 10.5% of PWH with incident TB were tested positive. Preventive treatment reduced the risk in LTBI test positive PWH for active TB (relative risk reduction, 28.1%, absolute risk reduction 0.9%). On population level, the increase of CD4 T-cells and reduction of HIV viral load were the main driver of TB decrease.

CONCLUSIONS

TB specific prevention is effective in selected patient groups. On a population level, control of HIV-1 remains the most important factor for incident TB reduction. Accurate identification of PWH at highest risk for TB is an unmet clinical need.

Facilitators and barriers to latent tuberculosis infection treatment among primary healthcare workers in Malaysia: a qualitative study

BACKGROUND

Healthcare workers (HCWs) have an increased risk of active and latent tuberculosis infection (LTBI) compared to the general population. Despite existing guidelines on the prevention and management of LTBI, little is known about why HCWs who tested positive for LTBI refuse treatment. This qualitative study sought to explore the facilitators and barriers to LBTI treatment uptake among primary HCWs in Malaysia.

METHODS

This qualitative study used a phenomenological research design and was conducted from July 2019 to January 2021. A semi-structured topic guide was developed based on literature and the Common-Sense Model of Self-Regulation. We conducted one focus group discussion and 15 in-depth interviews with primary care HCWs. Interviewees were 7 physicians and 11 allied HCWs who tested positive for LTBI by Tuberculin Skin Test or Interferon Gamma Release Assay. Audio recordings were transcribed verbatim and thematic analysis was used to analyse the data.

RESULTS

We found four factors that serve as barriers to HCWs' LTBI treatment uptake. Uncertainties about the need for LTBI treatment, alongside several other factors including the attitude of the treating physician towards treatment, time constraints during clinical consultations, and concerns about the treatment itself. On the other hand, facilitators for LTBI treatment uptake can be grouped into two themes: diagnostic modalities and improving knowledge of LTBI treatment.

CONCLUSIONS

Improving HCWs' knowledge and informative clinical consultation on LTBI and its treatment benefit, aided with a definitive diagnostic test can facilitate treatment uptake. Additionally, there is a need to improve infection control measures at the workplace to protect HCWs. Utilizing behavioural insights can help modify risk perception among HCWs and promote treatment uptake.

Prevalence and predictors of tuberculosis infection among people living with HIV in a high tuberculosis burden context

BACKGROUND

Tuberculosis (TB) disease is the leading cause of mortality among people living with HIV (PLHIV). Interferon-gamma release assays (IGRAs) are approved for TB infection ascertainment. However, current IGRA data on the prevalence of TB infection in the context of near-universal access to antiretroviral therapy (ART) and TB preventive therapy (TPT) are lacking. We estimated the prevalence and determinants of TB infection among PLHIV within a high TB and HIV burden context.

METHODS

This cross-sectional study included data from adult PLHIV age ≥18 years in whom QuantiFERON-TB Gold Plus (QFT-Plus) assay, an IGRA, was performed. TB infection was defined as a positive or indeterminate QFT-Plus test. Participants with TB and those who had previously used TPT were excluded. Regression analysis was performed to identify independent predictors of TB infection.

RESULTS

Of 121 PLHIV with QFT-Plus test results, females were 74.4% (90/121), and the mean age was 38.4 (SD 10.8) years. Overall, 47.9% (58/121) were classified as TB infection (QFT-Plus test positive and indeterminate results were 39.7% (48/121) and 8.3% (10/121), respectively). Being obese/overweight (body mass index ≥25 kg/m²; p=0.013, adjusted OR (aOR) 2.90, 95% CI 1.25 to 6.74) and ART usage for >3 years (p=0.013, aOR 3.99, 95% CI 1.55 to 10.28) were independently associated with TB infection.

CONCLUSION

There was a high TB infection prevalence among PLHIV. A longer period of ART and obesity were independently associated with TB infection. The relationship between obesity/overweight and TB infection may be related to ART use and immune reconstitution and requires further investigation. Given the known benefit of test-directed TPT among PLHIV never exposed to TPT, its clinical and cost implications for low and middle-income countries should be explored further.

Predictors for False-Negative Interferon-Gamma Release Assay Results in Hemodialysis Patients with Latent Tuberculosis Infection

The present study aimed to clinically evaluate the effect of T-cell dysfunction in hemodialysis (HD) patients with latent tuberculosis (TB) infection (LTBI) who were false-negatives in the QuantiFERON-TB Gold In-Tube (QFT-GIT) test. Whole blood samples from a total of 20 active TB patients, 83 HD patients, and 52 healthy individuals were collected, and the QFT-GIT test was used for measuring Mycobacterium tuberculosis (MTB)-specific interferon gamma (IFN-γ) level. The positive rate of the IFN-γ release assays (IGRAs) in HD patients was lower than the negative rate. The mean value of MTB-specific IFN-γ level, which determines the positive rate of the IGRA test, was highest in active TB, followed by HD patients and healthy individuals. Among HD patients, phytohemagglutinin A (PHA)-stimulated IFN-γ levels of approximately 40% were 10.00 IU/mL or less. However, there was no low level of PHA-stimulated IFN-γ in the healthy individuals. This reveals that T-cell function in HD patients was reduced compared to healthy individuals, which leads to the possibility that QFT-GIT results in HD patients are false-negative. The clinical manifestations of TB in patients on HD are quite non-specific, making timely diagnosis difficult and delaying the initiation of curative treatment, delay being a major determinant of outcome.

Comparison of interferon gamma release assay and CXCL9 gene expression assay for the detection of Mycobacterium bovis infection in African lions (Panthera leo)

Mycobacterium bovis (M. bovis) infection has been identified in both domestic and wild animals and may threaten the conservation of vulnerable species including African lions (Panthera leo). There is a need to develop accurate ante-mortem tools for detection of M. bovis infection in African big cat populations for wildlife management and disease surveillance. The aim of this study was to compare the performances of two immunological assays, the QuantiFERON®-TB Gold Plus (QFT) Mabtech Cat interferon gamma release assay (IGRA) and QFT CXCL9 gene expression assay (GEA), which have both shown diagnostic potential for M. bovis detection in African lions. Lion whole blood (n=47), stimulated using the QFT platform, was used for measuring antigen-specific CXCL9 expression and IFN-γ production and to assign M. bovis infection status. A subset (n=12) of mycobacterial culture-confirmed M. bovis infected and uninfected African lions was used to compare the agreement between the immunological diagnostic assays. There was no statistical difference between the proportions of test positive African lions tested by the QFT Mabtech Cat IGRA compared to the QFT CXCL9 GEA. There was also a moderate association between immunological diagnostic assays when numerical results were compared. The majority of lions had the same diagnostic outcome using the paired assays. Although the QFT Mabtech Cat IGRA provides a more standardized, commercially available, and cost-effective test compared to QFT CXCL9 GEA, using both assays to categorize M. bovis infection status in lions will increase confidence in results.

Diagnostic accuracy of the interferon-gamma release assay in acquired immunodeficiency syndrome patients with suspected tuberculosis infection: a meta-analysis

Purpose

The diagnostic accuracy of the interferon-gamma release assay (IGRA) in immunosuppressed patients remains unclear.

Methods

A systematic review and meta-analysis were performed for diagnostic test accuracy of IGRA in tuberculosis (TB) infection among people living with HIV (PLWHIV). Summary estimates of sensitivity and specificity were calculated using both univariate and bivariate models.

Results

The meta-analysis included 45 of the 1,242 first-screened articles. The total number of PLWHIV was 6,525; 3,467 had TB disease, including 806 cases of LTBI and 2,661 cases of active TB. The overall diagnostic odds ratio (DOR) of IGRA in the diagnosis of TB disease was 10.0 (95% confidence interval (CI) 5.59, 25.07), with an area under the curve (AUC) of 0.729. The DOR was better for QFT (14.2 (95%CI 4.359, 46.463)) than T-SPOT (10.0 (95%CI 3.866 26.033)). The sensitivity and specificity of QFT and T-SPOT were 0.663 (95%CI 0.471, 0.813), 0.867 (95%CI 0.683 0.942), and 0.604 (95%CI 0.481, 0.715), 0.862 (95%CI 0.654, 0.954), respectively, in the bivariate model. The sensitivity of IGRA in the diagnosis of LTBI was 0.64 (95%CI 0.61, 0.66).

Conclusion

IGRA was useful in the diagnostic of TB disease in PLWHIV, and QFT showed a better tendency of DOR than T-SPOT. IGRA showed a limited effect to rule out LTBI in PLWHIV.

Diagnostic value of interferon-γ release assay in HIV-infected individuals complicated with active tuberculosis: a systematic review and meta-analysis

OBJECTIVE

Although the interferon-γ release assay (IGRA) has become a common diagnostic method for tuberculosis, its value in the diagnosis of tuberculosis in human immunodeficiency virus (HIV) seropositive patients remains controversial. Therefore, this systematically reviews the data for exploring the diagnostic value of IGRA in HIV-infected individuals complicated with active tuberculosis, aiming to provide a clinical basis for future clinical diagnosis of the disease.

METHODS

Relevant studies on IGRA for diagnosing tuberculosis in HIV-infected patients were comprehensively collected from Excerpta Medica Database (EMBASE), Medline, Cochrane Library, Chinese Sci-tech Periodical Full-text Database, Chinese Periodical Full-text Database, China National Knowledge Infrastructure (CNKI) and China Wanfang Data up to July 2020. Subsequently, Stata 15.0, an integrated statistical software, was used to analyse the sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratio (PLR) and negative likelihood ratio (NLR) to create receiver operator characteristic (ROC) curves.

RESULTS

A total of 18 high-quality articles were selected, including 20 studies, 11 of which were related to QuantiFERON-TB Gold In-Tube (QFT-GIT) and nine to T-SPOT.TB. The meta-analysis indicated that the pooled sensitivity = 0.75 (95% CI 0.63-0.85), the pooled specificity = 0.82 (95% CI 0.66-0.92), PLR = 4.25 (95% CI 1.97-9.18), NLR = 0.30 (95% CI 0.18-0.50), DOR = 14.21 (95% CI 4.38-46.09) and the area under summary ROC curve was 0.85 (95% CI 0.81-0.88).

CONCLUSION

IGRA has a good diagnostic value and therefore can aid in the preliminary screening of active tuberculosis in HIV-infected individuals. Its diagnostic effectiveness can be improved by modifying and optimizing the assay design.

TST conversions and systemic interferon-gamma increase after methotrexate introduction in psoriasis patients

Background

Tuberculosis screening in psoriasis patients is complex due to the immunological alterations associated with psoriasis, the presence of comorbidities, and the effect of immunosuppressive treatment. However, it is not established whether the results of screening tests are affected by these factors in psoriasis patients.

Objectives

To determine whether there is a change in the results of the tuberculin skin test (TST) or the interferon-gamma release assay (IGRA) in psoriasis patients living in tuberculosis (TB)-endemic area after 12 weeks of methotrexate (MTX) treatment and to investigate the association of the test results with clinical and inflammatory markers.

Methods

Forty-five patients were selected for a prospective single-arm self-controlled study and followed for at least 18 months. The TST, IGRA, Psoriasis Area and Severity Index (PASI), and inflammatory factors (erythrocyte sedimentation rate (ESR), C-reactive protein, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha levels), were determined before and after 12 weeks of oral 15 mg per week MTX administration and compared. The associations between the IGRA and TST results were verified before and after treatment according to inflammatory factors and clinical characteristics (age, blood glucose, weight, body mass index, disease duration, and PASI).

Results

We collected data on 25 patients who completed the full course of therapy and the follow-up. None of the patients developed TB. TST positivity was significantly elevated at week 12 (25% baseline vs 44% at week 12, P < 0.037). Three IGRAs followed the TST conversions. There was no difference between TST and IGRA pre- or posttreatment. Serum IFN-γ increased significantly in week 12 (15.95 pg/ml baseline vs 18.82 pg/ml at week 12, P < 0.005) and tended to be higher among TST-positive patients (P = 0.072). The baseline IGRA was associated with a higher ESR (P = 0.038). None of the test results were associated with clinical characteristics.

Conclusions

In addition to the classic booster effect, TST conversions in patients using MTX can occur due to an increase in IFN-γ. However, it is not possible to exclude true TST conversions. Therefore, other diagnostic methods, like IGRA or chest tomography, should be used when the TST has intermediate results.

Comparison between the Interferon γ Release Assay-QuantiFERON Gold Plus (QFT-Plus)-and Tuberculin Skin Test (TST) in the Detection of Tuberculosis Infection in Immunocompromised Children

Background

Immunocompromised patients are at a higher risk of having latent tuberculosis infection (LTBI). QuantiFERON-TB Gold Plus (QFT-Plus) has been proven to perform effectively in LTBI detection among immunocompromised adults and can overcome the limitations of the tuberculin skin test (TST). However, the role of QFT-Plus in detecting LTBI in immunocompromised paediatric patients has not been well established. Therefore, the aim of this study was to assess the test agreement between QFT-Plus and the TST in LTBI detection among immunocompromised children.

Method

In this cross-sectional study, we enrolled immunocompromised paediatric patients, aged between 5 and 18 years, who were treated with corticosteroids and/or chemotherapy from June to November 2019. We categorized them into three groups based on the following diseases: hematologic malignancies and nephrological and immunological diseases. We recorded the patient characteristics and QFT-Plus and TST results, in which the positive result of the TST was induration ≥ 5 mm. Within the same group, comparisons between the two tests were performed using the McNemar test, and results were statistically significant for p values of <0.05. The kappa index was used to assess the agreement between the two test results.

Results

Among 71 patients (median age: 11.8 years) who underwent TST and QFT-Plus testing, 52% were females, and 69% had a normal nutritional status. Chemotherapy was the most common treatment modality for hematologic malignancy compared to other immunosuppressive treatments. The total number of patients with positive QFT-Plus and TST results was 11/71 (15.5%) and 4/71 (5.6%), respectively, among whom 3/11 patients had positive results in both tests, and one patient with positive TST results exhibited a discrepancy, as this was not followed by positive QFT-Plus results. QFT-Plus generated more positive results than the TST in immunocompromised children (McNemar, p = 0.039 (p < 0.05)). The diagnostic agreement between the tests was fair (K = 0.345, 95% CI: 0.05–0.745).

Conclusion

QFT-Plus detected LTBI more effectively than the TST in immunocompromised children.

The Prevalence and Demographic Risk Factors for Latent Tuberculosis Infection (LTBI) Among Healthcare Workers in Semarang, Indonesia

Purpose

To determine the prevalence and demographic risk factors for latent tuberculosis infection (LTBI) among healthcare workers in Semarang, Indonesia.

Methods

A cross-sectional study involving 195 healthcare workers from 34 primary health centers was conducted from August to October 2019. The relationship between independent variables and dependent variables was analyzed using a multivariable logistic regression analysis.

Results

The prevalence of LTBI among healthcare workers in this study was 23.6%. Comorbidities were the only risk factor for LTBI identified among other risk factors (OR=3.39, 95% CI: 0.99–11.62, p=0.04). Other demographic factors such as age (OR=0.93, 95% CI: 0.45–1.92, p=0.839), gender (OR=0.79, 95% CI: 0.23–2.72, p=0.708, smoking habits (OR=2.54, 95% CI: 0.52–12.38, p=0.247), and length of work (OR=1.43, 95% CI: 0.70–2.91, p=0.331) were not significant risk factors for LTBI.

Conclusion

Healthcare workers suffering from comorbidity have a high risk for tuberculosis infection, and should not work in areas where they would be exposed to patients with tuberculosis. Healthcare workers need to apply occupational safety standards during contact with TB patients or specimens to minimize the disease transmission.

Good Agreement between an Interferon Gamma Release Assay and Tuberculin Skin Tests in Testing for Latent Tuberculosis Infection among HIV-Infected Patients in Indonesia

BACKGROUND

Latent tuberculosis infection is a condition where there is a persistent immune response to Mycobacterium tuberculosis without clinical manifestations of tuberculosis. Currently, there is no gold standard to diagnose latent tuberculosis infection. The tuberculin skin test and interferon-gamma release assay are currently used to diagnose latent tuberculosis infection. However, studies have shown inconsistencies regarding the level of agreement between these tests in different settings. In this study, we aimed to evaluate the agreement between these two tests for diagnosing latent tuberculosis infection in human immunodeficiency virus (HIV)-infected individuals.

METHODS

We screened HIV patients with no clinical symptoms of tuberculosis, a normal chest X-ray, and no history of tuberculosis or use of antituberculous drugs. Participants were tested with tuberculin skin test (TST) and T-SPOT.TB (an interferon gamma release assay) simultaneously. Participants' HIV stage was determined by measuring the level of CD4+ T-lymphocytes. Tuberculosis status was confirmed by sputum examination using GeneXpert. The level of agreement between the TST and T-SPOT.TB results was measured using Cohen's κ coefficient.

RESULTS

Of the 112 participants, 20 had a positive T-SPOT.TB test result, and 21 had a positive TST result. The TST and T-SPOT.TB test results showed a high level of agreement (κ = 0.648, P < 0.001). Performance of the tests did not vary with CD4+ level. However, in participants with CD4+ < 200 cells/mm³, T-SPOT.TB detected more latent tuberculosis infections than the TST.

CONCLUSION

There was good agreement between the TST and T-SPOT.TB results of latent tuberculosis infection in participants. TST is the preferred test for diagnosing latent tuberculosis infection in HIV-infected patients, especially in resource-limited settings, because it is simple and cost-effective. However, T-SPOT.TB may be useful to rule out latent tuberculosis infection in patients with severe immunodeficiency.

Asymptomatic immune responders to Leishmania among HIV positive patients

Concomitant infection with human immunodeficiency virus (HIV) and the Leishmania parasite is a growing public health problem, the result of the former spreading to areas where the latter is endemic. Leishmania infection is usually asymptomatic in immunocompetent individuals, but the proportion of HIV+ individuals in contact with the parasite who remain asymptomatic is not known. The aim of the present work was to examine the use of cytokine release assays in the detection of asymptomatic immune responders to Leishmania among HIV+ patients with no previous leishmaniasis or current symptomatology. Eighty two HIV+ patients (all from Fuenlabrada, Madrid, Spain, where a leishmaniasis outbreak occurred in 2009) were examined for Leishmania infantum infection using molecular and humoral response-based methods. None returned a positive molecular or serological result for the parasite. Thirteen subjects showed a positive lymphoproliferative response to soluble Leishmania antigen (SLA), although the mean CD4+ T lymphocyte counts of these patients was below the normal range. Stimulation of peripheral blood mononuclear cells (PBMC) or whole blood with SLA (the lymphoproliferative assay and whole blood assay respectively), led to the production of specific cytokines and chemokines. Thus, despite being immunocompromised, HIV+ patients can maintain a Th1-type cellular response to Leishmania. In addition, cytokine release assays would appear to be useful tools for detecting these individuals via the identification of IFN-γ in the supernatants of SLA-stimulated PBMC, and of IFN-γ, MIG and IL-2 in SLA-stimulated whole blood. These biomarkers appear to be 100% reliable for detecting asymptomatic immune responders to Leishmania among HIV+ patients.

The proportion of patients with HIV+ who have at some time been infected with the Leishmania parasite, but who remain asymptomatic, is unknown. It is important to be able to identify such patients to determine the prevalence of asymptomatic leishmaniasis in the HIV+ population, and because these persons are at increased risk of developing symptomatic visceral leishmaniasis. In the present work, a population of HIV+ patients showing a cellular immune response to Leishmania infantum was identified. These subjects all showed a clear Th1-type response when their PBMC or blood were stimulated in vitro with soluble Leishmania antigen (SLA). Cytokine release assays and the detection of IFN-γ, MIG and IL-2 (specific biomarkers for immunity to Leishmania) were found to be useful for detecting this population of HIV+ patients. New studies with larger numbers of patients are needed to confirm the present results.