Abstract Rationale Differentiating sarcoidosis from tuberculosis (TB) remains a diagnostic challenge. A positive Tuberculin Skin Test (TST) has traditionally been considered for ruling out sarcoidosis. However, patients with Sarcoidosis can demonstrate TST-reactivity. Using TST reactivity to diagnose TB has the potential for misdiagnosing patients with sarcoidosis who do not have concurrent TB. We aimed to study the characteristics of TST-reactive sarcoidosis patients in India. Methods This retrospective observational study included histologically diagnosed sarcoidosis patients from a large Sarcoidosis cohort at a tertiary care centre in India between January 2013 and July 2019. Ethical approval was obtained. All patients underwent standardised clinical, radiological, and laboratory evaluation. Histological confirmation was obtained through bronchoscopy, endosonography, or extrathoracic sampling, depending on the site of involvement. Data were recorded in the REDCap (Research Electronic Data Capture) portal, and analyses were performed. Results We compared 211 TST-anergic and 80 TST-reactive patients with sarcoidosis. The two groups were similar in age (mean 42.7 ± 10.5 vs 41.9 ± 10.6 years) and had comparable gender distributions (Males 53.6% vs 45.0%, Females 46.4% vs 55.0%). Visual symptoms were noted in 16/200 (8.0%) symptomatic TST-anergic and 18/79 (22.8%) symptomatic TST-reactive patients (p 0.001). Mediastinal lymph node calcification was observed in 22/198 (11.1%) TST-anergic and 19/78 (24.4%) TST-reactive patients (p = 0.005). Endobronchial biopsy detected granulomas (necrotising and non-necrotising) in 59/145 anergic patients (40.7%) versus 13/58 reactive patients (22.4%) (p = 0.014). Transbronchial lung biopsy detected granulomas (necrotising and non-necrotising) in 94/150 anergic patients (62.7%) compared to 29/62 reactives (46.8%) (p = 0.033). Thus, mucosal and lung biopsies were significantly more likely to demonstrate granulomas in TST-anergic sarcoidosis. There were no other significant differences in most of the clinical characteristics and outcomes of patients from both subgroups. Conclusions TST-anergic and reactive sarcoidosis patients demonstrated broadly similar demographic and clinical characteristics. However, visual symptoms and mediastinal lymph node calcification were significantly more frequent among TST-reactive patients, whereas endobronchial and transbronchial biopsies showed higher granuloma detection rates in the anergic subgroup. Hence, given the broadly similar characteristics between the two subgroups, the presence of TST reactivity should not exclude the diagnosis of sarcoidosis. The similarity in most of the clinical features supports that TST reactive sarcoidosis is a distinct entity, and the presence of tuberculin reactivity in isolation should not lead to exclusion of the diagnosis of sarcoidosis. Further studies are warranted to elucidate the relationship between mycobacterial exposure and sarcoidosis development, especially in TB-endemic settings. This abstract is funded by: None
Bharathkumar et al. (Fri,) studied this question.