Unveiling the Silent Threat: Exploring Latent Tuberculosis in Multiple Sclerosis Patients Undergoing Novel Therapies

Introduction:

Latent tuberculosis, defined as positive IGRA or positive PPD (> 5 mm) in the absence of clinical or radiological signs of active TB or other confounding factors, prevails in a quarter of the world's population. About 10% of latent TB carriers may develop active TB, especially in the context of immunosuppression. Such context is constantly experienced by multiple sclerosis (MS) patients using Disease Modifying Drugs, raising concerns about their impact on increased incidence of latent TB and conversion to active TB. Screening for latent TB is not always recommended and/or performed in MS patients, so data from this subgroup, especially in endemic countries, is scarce.

Objective:

To define the prevalence of latent TB in MS patients screened for prescription of Alemtuzumab, Rituximab, and Oral Cladribine at a reference center in an endemic country for tuberculosis, evaluate risk factors for latent TB (e.g., smoking, diabetes) in the screened population, as well as characteristics of MS (e.g., gender, age, disease duration) in the latent TB subgroup compared to the TB-negative subgroup.

Methods:

Subgroups with and without latent TB were defined and compared in a sample of 60 MS patients screened for prescription of Alemtuzumab, Rituximab, and Oral Cladribine. Fisher's exact test was used to compare qualitative variables, while the Mann-Whitney test (non-parametric) was employed for quantitative variables. Statistical significance was established as p < 0.05.

Results:

Frequency of latent TB in the sample was approximately 24%. Smoking was the only factor presented that correlated with a higher chance of latent TB.

Conclusion:

The frequency of latent TB was significantly higher, as expected, than in similar studies conducted in North America and Europe but similar to the prevalence of the general population in endemic countries. Larger sampling is necessary to adequately correlate prevalence, risk factors for latent TB, and MS characteristics.