A comparison of the clinical profile of Sarcoidosis and Mediastinal TB: A prospective cohort study in a TB endemic population

Introduction: Differentiating Sarcoidosis from Mediastinal TB is challenging, especially in TB endemic settings. There is scant literature on the comparative clinical profile of patients with histologically confirmed Sarcoidosis and Mediastinal TB. Aim: To compare the clinical profile, diagnostic investigations, and pathological findings among patients with Sarcoidosis and Mediastinal TB. Methods: Ethical approval was obtained. We prospectively enrolled subjects with a diagnosis of Sarcoidosis and Mediastinal TB from the chest clinic at a tertiary care referral facility. Treatment response at six-months was considered as the gold standard for diagnosis. Results: Compared to Mediastinal TB (n=115), patients with Sarcoidosis (n=327) were younger, had a higher BMI, longer symptom duration (308 ± 27 vs. 114 ± 11 days) and higher prevalence of diabetes and hypothyroidism. Breathlessness and cough were more frequent, while fatigue and anorexia were more common in Mediastinal TB. Serum ACE levels, urine 24-hr calcium, and blood eosinophil count were higher in sarcoidosis. Significantly more subjects with Sarcoidosis were tuberculin anergic (71.9 % vs. 7.8 %). Necrotic lymph nodes and single nodal station involvement on CT were higher in mediastinal TB. On Endobronchial Ultrasound (EBUS), coagulation necrosis sign (26.2% vs. 2.3%) and heterogenous node appearance (51.4% vs. 4.9%) were more frequent in TB. On pathology, necrosis or necrotizing granulomas were more common in TB (55.6% vs. 13.5%) compared with Sarcoidosis. Conclusion: A comprehensive clinical, radiological and pathological approach may allow accurate differentiation of Sarcoidosis from Mediastinal TB.