Latent Tuberculosis in Psoriasis Patients Planned for Systemic Therapy – A Prospective Observational Study

BACKGROUND: India has a high prevalence of tuberculosis and latent tuberculosis infection (LTBI) is common in the general population. LTBI can progress to active tuberculosis in almost 10% patients and the risk increases with immunosuppression. This predisposes patients of psoriasis on systemic therapy for the development of active tuberculosis. AIMS: To find the prevalence of LTBI in patients with psoriasis planned for systemic therapy. METHODOLOGY: It was a prospective observational study conducted in a tertiary care center during period Jan-Dec 2019. Patients older than 18 years with chronic plaque psoriasis planned for systemic therapy and willing to be part of the study were included. Baseline clinical data were collected. Radiograph of chest and tuberculin skin test (TST) was performed in all patients. Detailed evaluation including sputum examination and computed tomography of the chest and abdomen were performed in patients with TST >10 mm. RESULTS: A total of 105 patients met the inclusion criteria of the study, with the mean age of patients being 29.5 ± 2.12 years. Out of these patients, 58 were males and 47 females. The mean duration of psoriasis was 2.95 ± 1.3 years. The mean PASI score was 16.71 ± 4.384. Mantoux was positive (>10 mm) in 33 (31.42%) patients. Two patients were found to have features of active tuberculosis based on imaging and microbiological investigations. Totally, 31 (29.5%) patients had LTBI and were treated with isoniazid and rifampicin for three months while 2 (1.9%) patients were treated with four drugs antitubercular regimen. LIMITATIONS: Small sample size, convenience method of sampling and study population limited to those visiting medical college hospital are its major limitations. CONCLUSION: LTBI is common in study population and screening for LTBI should be performed in all patients of psoriasis planned for systemic therapy. A thorough search for active tuberculosis should be performed. Timely detection of LTBI helps in the prevention of development of active tuberculosis in the patients on immunosuppressive treatment.