Positiveness of purified protein derivatives in rheumatoid arthritis patients who are not receiving immunosuppressive therapy

Screening for latent tuberculosis infection among patients with rheumatoid arthritis in the era of biologics and targeted synthetic disease-modifying anti-rheumatic drugs in India, a high-burden TB country: The importance of Mantoux and Quantiferon-TB Gold tests

AIM

To test the validity of an augmented tuberculosis skin test (a-TST) combined with Quantiferon TB-gold^® (QFTG) test for the screening of latent tuberculosis infection (LTBI) in patients with rheumatoid arthritis (RA) being considered for treatment with biologic disease-modifying anti-rheumatic drugs or targeted synthetic disease-modifying anti-rheumatic drugs.

METHOD

Standard TST using 1 tuberculin unit (TU) of purified protein derivative (PPD, RT23 strain) was carried out. If the positivity was less as compared to the general population, then a-TST using 10 TU PPD was employed. Simultaneously, QFTG test was also performed.

RESULTS

Using standard TST, 6/44 (13.6%), patients were positive compared to the reported figures of ~ 40% of the general population; 38 of the remaining TST-negative patients were then given an a-TST with 10 TU PPD; eight of them dropped out. Of the remaining 30 patients, eight (26.6%) were positive. Another 70 patients tested directly with a-TST; 22 (31.4%) were found positive. Thus, of a total of 100 patients tested with a-TST, 30 (30%) were positive. In 54 a-TST negative patients, QFTG was done; seven (13%) were positive. Thus, in combined a-TST with QFTG, 43% of the RA patients were found positive, suggestive of the presence of LTBI.

CONCLUSION

Combined a-TST with QFTG testing gave 43% positivity among RA patients, which is close to the reported ~ 40% Mantoux positivity in the general population. Therefore, this method for the screening of LTBI in Indian patients with RA being considered for tumor necrosis factor alpha treatment could be satisfactory for offsetting TB flare. It may apply to other high-burden TB countries around the world.

Purified protein derivative test and its booster phenomenon in patients with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a common disease in the community, with various complications. An appropriate solution is immunosuppressive drugs, which may lead to weakening of the cellular immune system and body unresponsiveness to tuberculosis (TB). As TB sensitivity is determined by the amount of induration created in the Purified Protein Derivative (PPD) test, this study aims to evaluate the immune response to the PPD test and its booster in RA patients.

MATERIALS AND METHODS

This cross-sectional study was performed on rheumatoid arthritis patients referred to Alzahra Hospital, Isfahan, treated with ‹20 mg glucocorticoid daily or 7.5 mg Methotrexate (MTX) weekly. The sampling method was simple and accessible. The PPD test was performed in patients using the Mantoux method after 72 hours, and seven days later, the results were interpreted in 72 hours after the PPD booster injection. Induration ≥5 mm was considered to be positive. The data was analyzed using the SPSS software.

RESULTS

Nineteen patients had positive results in the initial and reminder tests and 81 patients had negative results in both tests. Six patients (6.9%) with negative results in the initial test changed to positive in the reminder test. There was no positive result in the initial test and negative result in the reminder one. The frequency distribution of the reminder test, based on the initial test was significant (P < 0.001). Also, the McNemar test showed that the changes in the reminder test based on the initial test had a significant difference (P = 0.031).

CONCLUSION

It seems that in the endemic and developing areas, the PPD booster is applicable for diagnosing latent tuberculosis in patients with rheumatoid arthritis.

Challenges in Diagnosing Latent Tuberculosis Infection in Patients Treated with Tumor Necrosis Factor Antagonists

Reactivation of latent tuberculosis infection (LTBI) is well recognized as an adverse event associated with anti-tumor necrosis factor-α (anti-TNF-α) therapy. The strengths and weaknesses of current techniques for detecting LTBI in patients with chronic inflammatory diseases such as rheumatoid arthritis (RA) and psoriasis have not been fully examined. T cell hyporesponsiveness due to immunosuppression caused by illness or drugs, referred to as anergy, may produce false-negative tuberculin skin test (TST) and interferon-γ release assay (IGRA) results. The literature suggests that anergy may influence screening performance of TST and IGRA tests in candidates for anti-TNF-α therapy. Conversely, the potential for false-positive TST and IGRA results must be considered, as treatment for LTBI may be associated with significant morbidity. This review examines the reliability issues related to LTBI diagnostic testing and provides practical direction to help prevent LTBI reactivation and facilitate successful anti-TNF-α treatment.

[Tuberculosis in rheumatoid arthritis patients: the difficulty in making the diagnosis of latent infection]

Since the beginning of the use of anti-TNF in the treatment of rheumatoid arthritis and other inflammatory diseases, cases of pulmonary tuberculosis and extrapulmonary tuberculosis have been reported in patients receiving such treatment. In most cases, the disease develops by the time the patient has received the sixth infusion. Every patient should be evaluated for latent tuberculosis infection prior to the use of a TNF inhibitor. However, the diagnosis of latent tuberculosis infection is a challenge. The tuberculin test, which was the only test available to detect latent tuberculosis infection for nearly a century, presents a number of limitations. Tests based on the detection of the in-vitro production of IFN-gamma by mononuclear cells activated by specific antigens appear to be more accurate and have been studied in patients with rheumatoid arthritis.