Bronchiolitis Obliterans Syndrome After Lung Transplant MCQ — NEET PG Practice Question | NEETPGAI
Bronchiolitis Obliterans Syndrome After Lung Transplant
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stethoscope Medicine
A 52-year-old man undergoes bilateral lung transplantation for idiopathic pulmonary fibrosis. His baseline best FEV₁ (average of two measurements ≥3 weeks apart) is 3.2 L (100% predicted). At 18 months post-transplant, he presents with insidious dyspnea and dry cough. Spirometry shows FEV₁ of 2.5 L. Transbronchial biopsy shows no acute rejection, bronchoalveolar lavage is negative for infection, and bronchoscopy reveals no anastomotic complications. The structure marked **B** in the diagram—Bronchiolitis Obliterans Syndrome (BOS)—is suspected. According to ISHLT consensus criteria, what percentage decline in FEV₁ from baseline best FEV₁ is required to operationally define BOS?
A. ≥15% sustained decline beyond 3 weeks
B. ≥30% sustained decline beyond 4 weeks
C. ≥10% sustained decline beyond 2 weeks
D. ≥20% sustained decline beyond 3 weeks
Explanation
Why ≥20% sustained decline beyond 3 weeks is right
The ISHLT consensus definition of Bronchiolitis Obliterans Syndrome (BOS) requires a sustained decline of ≥20% in FEV₁ from the baseline best FEV₁, measured as the average of at least two measurements taken ≥3 weeks apart in the first post-transplant year, and this decline must persist beyond 3 weeks in the absence of acute rejection, infection, or anastomotic complications. In this case, the patient's FEV₁ dropped from 3.2 L to 2.5 L, representing a 22% decline—meeting the threshold for BOS-1 (66–80% of baseline). This 20% threshold is the operational ISHLT definition and the most reliable criterion for diagnosing BOS as the most common form of chronic lung allograft dysfunction (CLAD). [ISHLT Consensus on CLAD 2024; Verleden GM J Heart Lung Transplant 2019]
Why each distractor is wrong
≥10% sustained decline beyond 2 weeks: This threshold is too lenient and would capture normal physiologic variation and minor fluctuations in post-transplant spirometry. The ISHLT definition specifically requires ≥20%, not 10%, to reduce false-positive diagnoses.
≥30% sustained decline beyond 4 weeks: While a 30% decline would certainly indicate BOS, the ISHLT operational definition uses 20% as the threshold, not 30%. Using 30% would delay diagnosis and miss earlier-stage disease (BOS-0p, BOS-1).
≥15% sustained decline beyond 3 weeks: Although this is closer to the correct threshold, 15% is still below the ISHLT-defined 20% cutoff. This would risk overdiagnosis and misclassification of patients with borderline or reversible spirometric changes.
High-YieldNEET PG
BOS is defined by a ≥20% FEV₁ decline from baseline best FEV₁ (average of ≥2 measurements ≥3 weeks apart), sustained beyond 3 weeks, in the absence of acute rejection, infection, or anastomotic obstruction—the most common form of CLAD post-lung transplant.
