Incremental Diagnostic Yield of Bronchoscopy in Non-Resolving Pneumonia: A Prospective Observational Study from Eastern India

Technical Summary: Incremental Diagnostic Yield of Bronchoscopy in Non-Resolving Pneumonia

Problem Statement
Non-resolving pneumonia (NRP), defined as the failure of radiological resolution by at least 50% within two weeks or incomplete resolution within four weeks despite appropriate antimicrobial therapy, presents a significant diagnostic challenge. This is particularly acute in tuberculosis-endemic settings like Eastern India, where the etiology is highly heterogeneous, ranging from refractory bacterial infections and mycobacterial illnesses to occult neoplasms and inflammatory syndromes. While initial evaluations rely heavily on non-bronchoscopic methods (sputum testing, serology, image-guided biopsies), these approaches frequently yield inconclusive results when definitive diagnosis requires cytological evidence or deep tissue sampling. The study addresses the gap in understanding the specific value added by bronchoscopy when utilized as a secondary step after failed non-invasive evaluation.

Methodology
This prospective observational study was conducted at a tertiary care center in Eastern India (Kalinga Institute of Medical Sciences) between June 2024 and December 2025.

• Study Population: 130 adult patients (≥18 years) admitted with NRP.
• Exclusion Criteria: Patients with pre-diagnosed lung malignancy, sputum-positive pulmonary tuberculosis, hemodynamic instability, recent myocardial infarction, known HIV, coagulation disorders, or refusal of bronchoscopy were excluded.
• Diagnostic Protocol: A structured stepwise approach was employed:
  1. Non-Bronchoscopic Evaluation: All patients underwent sputum microbiological investigations (AFB smear, NAAT, Gram stain/culture, fungal studies), routine labs, and radiological assessment (CXR, CT). Selected patients received autoimmune serology or image-guided biopsies.
  2. Bronchoscopic Evaluation: Indicated for patients with inconclusive non-bronchoscopic findings. Procedures included bronchoalveolar lavage (BAL), bronchial brush cytology, and transbronchial lung biopsy (TBLB) using a fiberoptic video bronchoscope.
• Outcome Measures: The primary outcome was diagnostic yield (proportion of definitive etiological diagnoses). The secondary outcome was the incremental diagnostic yield of bronchoscopy (additional diagnoses established in patients with prior inconclusive non-bronchoscopic results).
• Statistical Analysis: Data were analyzed using SPSS v26.0. McNemar's test was used for paired categorical comparisons, and logistic regression was employed to identify predictors of yield.

Key Results

• Baseline Characteristics: The cohort had a median age of 51 years with 65.4% male predominance. Cough (98.5%) and fever (86.9%) were the most common symptoms. Radiologically, single-lobe involvement was most frequent (53.1%).
• Non-Bronchoscopic Yield: Initial non-bronchoscopic methods established a diagnosis in only 40.0% (n=52) of patients, primarily identifying tuberculosis (20.0%) and bacterial infections (19.2%). Consequently, 60.0% (n=78) remained undiagnosed.
• Bronchoscopic Yield: Bronchoscopy achieved an overall diagnostic yield of 66.2% (n=86).
  • Modalities: Bronchoalveolar lavage (BAL) contributed most significantly (33.8%), followed by TBLB (25.4%) and bronchial brush cytology (6.9%).
  • Incremental Yield: Crucially, bronchoscopy established a diagnosis in an additional 34 patients (26.2% of the total cohort) who had remained undiagnosed after non-bronchoscopic evaluation. This incremental gain was statistically significant (McNemar χ² = 4.21, p = 0.040).
• Etiological Spectrum: Among the 86 patients diagnosed via bronchoscopy, the distribution was:
  • Tuberculosis: 45.1%
  • Malignancy: 31.4%
  • Fungal infections: 19.6%
  • Others: 3.5%
  • Note: Bronchoscopy was particularly effective in identifying malignancy and fungal infections, which were rarely detected by non-bronchoscopic methods.
• Predictors: While univariate analysis suggested smoking history and dyspnea were associated with higher yield, multivariable logistic regression found no clinical variables to be independent predictors of diagnostic success.

Significance and Claims
The paper asserts that while non-bronchoscopic methods remain valuable as initial screening tools—especially for tuberculosis in endemic regions—they are insufficient for a majority of NRP cases. The study's primary contribution is the quantitative validation of a sequential diagnostic framework.

The authors claim that bronchoscopy provides a "significant incremental diagnostic yield" and plays a "central role" in establishing definitive etiological diagnoses for patients with inconclusive initial findings. Specifically, the study highlights that:

1. Malignancy and Fungal Detection: Bronchoscopy is critical for identifying pathologies (malignancy, fungal infections) that mimic infectious processes radiologically but require histopathological or cytological confirmation.
2. Clinical Decision-Making: The inability of baseline clinical variables to predict bronchoscopic success implies that the decision to escalate to bronchoscopy should be driven by the chronicity of findings and the failure of initial testing, rather than specific patient symptoms.
3. Avoidance of Empirical Therapy: By securing definitive diagnoses, the procedure helps avoid the hazards of prolonged, inappropriate empirical anti-tubercular or antimicrobial regimens, which is a common risk in tuberculosis-endemic zones where NRP is often misdiagnosed as refractory TB.

The study concludes that a stepwise approach—exhausting non-invasive options followed by targeted bronchoscopy—accelerates definitive diagnosis and improves patient outcomes. The authors modestly acknowledge limitations, including the single-center nature of the study and potential selection bias, noting that the true diagnostic potential of combined bronchoscopic modalities might be slightly underestimated as not all modalities were applied to every subject.