B69-09 An Insight From a Prospective Diagnostic Study: Induced Versus 24-hour Pooled Sputum Cbnaat in Spot-negative Suspected Pulmonary Tuberculosis

Rationale Patients with a strong clinical suspicion of pulmonary tuberculosis (PTB) but negative initial spot CBNAAT (GeneXpert) results present a common diagnostic dilemma. Simple, low-cost sampling approaches such as induced sputum or 24-hour pooled sputum may enhance diagnostic yield before bronchoscopy. However, comparative data using molecular tests are limited. Methods We conducted a prospective, single-center study in adults (n = 50) with suspected PTB and negative initial spot CBNAAT. Each participant provided both an induced sputum sample (following hypertonic-saline nebulization) and a 24-hour pooled sputum sample for repeat CBNAAT testing. Mycobacterial culture or a composite clinical diagnosis served as the reference standard. Diagnostic sensitivity, specificity, accuracy, and yield were compared between methods. Results Induced sputum CBNAAT: Sensitivity 81.5%, specificity 100%, accuracy 90%.24-hour pooled sputum CBNAAT: Sensitivity 55.6%, specificity 100%, accuracy 76%.Diagnostic yield: 42% vs 30%, respectively (p < 0.05). Induced sputum CBNAAT detected additional TB cases, particularly among patients with high clinical suspicion of PTB. Conclusions Induced sputum CBNAAT demonstrates significantly higher sensitivity and diagnostic yield compared to 24-hour pooled sputum CBNAAT among patients who are spot-CBNAAT negative. Adoption of induced sputum as a second-line diagnostic step may enhance case detection and reduce the need for invasive procedures in resource-limited settings. This abstract is funded by: None