Interobserver agreement in determining non-small cell lung cancer subtype in specimens acquired by EBUS-TBNA

Endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration (TBNA) may diagnose suspected lung cancer. Determination of non-small cell lung cancer (NSCLC) subtype may guide therapy in select patients. Small-volume biopsies may be subject to significant interobserver variability in subtype determination. Three pathologists independently reviewed specimens from 60 patients who underwent EBUS-TBNA for diagnosis/staging of suspected/known NSCLC. Smear, haematoxylin and eosin (H&E) and immunohistochemistry (IHC) specimens were reviewed without reference to other specimen types obtained from the same patient. Final diagnoses, and degree of confidence in the diagnosis, were recorded for each specimen. Almost perfect agreement was seen for distinguishing between small cell lung cancer and NSCLC for all specimen types. Agreement in determination of NSCLC subtype for smear, H&E and IHC specimens was slight (κ=0.095, 95% CI -0.164-0.355), fair (κ=0.278, 95% CI 0.075-0.481) and moderate (κ=0.564, 95% CI 0.338-0.740), respectively. Perfect agreement was seen when all three observers were confident of diagnoses made on IHC specimens. Interobserver agreement in interpretation of EBUS-TBNA specimens is moderate for determination of NSCLC subtype. Agreement is highest following examination of IHC specimens. Clinicians should be aware of the degree of pathologist confidence in the tissue diagnosis prior to commencement of subtype-specific therapy for NSCLC.