The minimal clinically important difference for the Sniffin’ Sticks Identification Test-16 in patients with chronic rhinosinusitis with nasal polyps treated with biologics

Background: The Minimal Clinically Important Difference (MCID) reflects the smallest change in a test score perceived as relevant by the patient. MCIDs vary according to disease and clinical context. The Sniffin’ Sticks Identification Test 16 (SSIT-16) is a commonly used smell assessment tool, but its MCID in severe chronic rhinosinusitis with nasal polyps (CRSwNP) is unknown. Objective: To determine the MCID of SSIT-16 in severe CRSwNP treated with biologics. Materials and methods: We analysed change scores from baseline to week 24 in 313 patients. The MCID was estimated using anchor-based and distribution-based methods. Anchors included a visual analogue scale (VAS) for smell, the rhinologic domain of SNOT-22, and the smell/taste item of SNOT-22. Distribution-based analyses included half a standard deviation of baseline SSIT-16 scores, the standard error of measurement (SEM), and the individual-level smallest detectable change. Results: The smell VAS performed best and was therefore chosen as the primary anchor. The optimal ΔSSIT-16 cut-off, balancing sensitivity (78%) and specificity (84%), was 3.5 points. This estimate was supported by distribution-based, sensitivity, and subgroup analyses. Conclusion and significance: An improvement of approximately 3.5 SSIT-16 points appears to reflect clinically meaningful change in biologically treated patients with severe CRSwNP and may serve as a pragmatic threshold for interpreting olfactory outcomes.