Tuberculin skin test and ELISPOT/T. SPOT.TB in children and adolescents with juvenile idiopathic arthritis

Spotlight on latent tuberculosis infection screening for juvenile idiopathic arthritis in two countries, comparing high and low risk patients

Background

Rheumatic diseases are associated with an increase in overall risks of tuberculosis (TB). The aim of this study was to evaluate the frequency of TB and the frequency of latent TB infection (LTBI), in clinical practice, for juvenile idiopathic arthritis (JIA) patients from high and low risk of TB incidence endemic countries.

Methods

This is an international, multicenter, cross-sectional, observational study of data collection from Brazil and Registry of Portugal at REUMA.PT. The inclusion criteria were patients with Juvenile Idiopathic Arthritis (JIA) with age ≤ 18 years who underwent screening for Mycobacterium tuberculosis infection [tuberculin skin test (TST) and/or interferon gamma release assay (IGRA)]. Chest X-rays and history of exposure to TB were also assessed.

Results

292 JIA patients were included; mean age 14.3 years, mean disease duration 7.5 years, 194 patients (66.4%) performed only TST, 14 (4.8%) only IGRA and 84 (28.8%) both. The frequency of LTBI (10.6%) and TB was similar between the two countries. The reasons for TB screening were different; in Brazil it was performed more often at JIA onset while in Portugal it was performed when starting Disease Modified Anti-Rheumatic Drugs (DMARD) treatment (p < 0.001). Isoniazid therapy was prescribed in 40 (13.7%) patients (31 with LTBI and 9 with epidemiologic risks and/or due to contact with sick people). Only three patients (1%) developed active TB.

Conclusion

We found nearly 10% of patients with LTBI, a small percentage of patients with treatment due to epidemiologic risks and only 1% with active TB. Distinct reasons and screening methods for LTBI were observed between the two countries.

Lateral Flow Genochromatographic Strip for Naked-Eye Detection of Mycobacterium Tuberculosis PCR Products with Gold Nanoparticles as a Reporter

Background

Mycobacterium tuberculosis (MTB) is a pathogen causing tuberculosis (TB) in human, and TB can cause enormous social and economic disruptions. Lateral flow test strips (LFTSs) are inexpensive, portable, disposable, rapid, and easy-to-use analytical tools.

Objective

LFTSs were prepared for the detection of MTB. LFTSs were fabricated using a new specific probe for MTB H37Rv, based on IS6110 sequence gene, and tailed with poly deoxyadenine (dA).

Material and Methods

In this experimental study, to create test and control zones, streptavidin (STP) and a 150-mer dA were dotted on a nitrocellolose membrane. Gold nanoparticles (GNPs) were conjugated with poly deoxythymidine sequence and placed on the conjugate pad. The composition of immersion buffers for sample pad and conjugate pad, running solution, solutions of GNPs-S-dT150 and STP were introduced. DNA genome of MTB and Mycobacterium bovis in clinical samples was amplified with PCR, and then detected by the LFTSs. During the assay, samples were firstly hybridized in two steps and then placed on a conjugate pad in a manner that positive and negative samples provided two and one red lines, respectively, on the detection pad.

Results

After PCR reaction with biotinylated primer, hybridization process with specific MTB probe-dA70-100 toke 10 min, and running process on the strip was performed within 5 min.

Conclusion

We showed that LFTS can discriminate a particular bacteria strain from others. The LFTSs can be redesigned for detection of other pathogenic genomes.

High rates of tuberculin skin test positivity due to methotrexate therapy: False positive results?

RATIONALE

The tuberculin skin test (TST) and interferon ? release assays (IGRAs) are commonly used for latent tuberculosis infection (LTBI) screening. Unexpectedly high TST positivity rates have been reported in patients with rheumatic diseases, and methotrexate is frequently used in this population. We hypothesized that methotrexate use could be associated with false-positive TST results.

OBJECTIVES

To investigate whether treatment with methotrexate and other factors are associated with false-positive TST results in patients with rheumatic diseases.

METHODS

Prospective single-center study conducted between April 2013 and March 2016. Adult patients with rheumatic diseases were evaluated with a TST and two IGRAs for LTBI screening. We compared TST and IGRA results in patients treated and not treated with methotrexate and analyzed for factors associated with positive TST results.

CONCLUSIONS

Our data suggest false-positive TST results associated with methotrexate therapy. Thus, we recommend against using the TST for LTBI screening in patients receiving methotrexate and the preferential use of IGRAs in such patients.

MEASUREMENTS AND MAIN RESULTS

We studied 393 patients with rheumatic diseases, including ankylosing spondylitis (ASP, n = 90), rheumatoid arthritis (RA; n = 120), psoriatic arthritis (PA, n = 126), and other disorders (n = 57). The rate of TST positivity varied across the groups: ASP 22.2%, RA 25%, PA 35.7%, and other disorders (22.8%). Positivity rates were lower with IGRAs. Methotrexate use was associated with a statistically significant two-fold increase in the risk of a positive TST and a dose\x96 response relationship was observed. We found no statistically significant associations between methotrexate use and IGRA test positivity.

Latent tuberculosis infection screening in juvenile idiopathic arthritis patients preceding anti-TNF therapy in a tuberculosis high-risk country

OBJECTIVES

To evaluate, in an endemic country, the long-term efficacy of latent tuberculosis infection (LTBI) screening and primary prophylaxis in patients with JIA receiving TNF blockers.

METHODS

This was a retrospective cohort that included JIA patients eligible to anti-TNF therapy. Patients were screened for LTBI prior to anti-TNF using tuberculin skin test (TST), chest X-ray and history of exposure to TB. Subjects were regularly followed at 2-month intervals.

RESULTS

Sixty-nine JIA patients with current age of 17.4±5.8 years, mean disease duration of 5.0±4.9 years were included. Forty-seven patients received a single anti-TNF, while 22 patients switched to another anti-TNF once or twice: 57 were treated with etanercepte, 33 patients with adalimumab and 3 infliximab. LTBI screening was positive in three patients: one had TST-positive and history of TB exposure and two had solely TST-positive. No active TB was diagnosed during the study period (median of follow-up was 3.8 years).

CONCLUSION

Long-term evaluation revealed that LTBI screening and primary prophylaxis before anti-TNF treatment was effective in a high-risk country and TST was the most sensitive parameter to identify these patients.