Sensitivity analysis and diagnostic accuracy of the Brief Smell Identification Test in patients with chronic rhinosinusitis

Background: The Brief Smell Identification Test (BSIT) is an abbreviated version of the Smell Identification Test (SIT) used to assess olfactory function. Although the BSIT can be efficiently administered in under 5 minutes, the accuracy of the BSIT in relation to the SIT in patients with chronic rhinosinusitis (CRS) is unknown. Methods: Patients with CRS were recruited as part of an ongoing multi-institutional observational cohort study. A total of 183 participants provided both BSIT and SIT olfactory function scores during initial enrollment. Linear associations between BSIT and SIT scores were evaluated using Pearson's correlation coefficients (r_p). The sensitivity, specificity, and accuracy of BSIT scores were determined using SIT scores as the "gold standard." Results: A strong bivariate linear association was found between BSIT and SIT scores (r_p = 0.893; p < 0.001) for all participants. A significantly lower proportion of patients were identified as having abnormal olfaction using the BSIT compared to the SIT (47% vs 68%, respectively; p < 0.001). Using the currently defined score of ≤8 as a cut-point for abnormal olfactory function, the BSIT demonstrated a sensitivity of 63% and specificity of 88% with an overall accuracy of 71%. Increasing the cut-point to ≤9 resulted in an increased sensitivity of 86%, a specificity of 76%, and an improved overall accuracy of 83%. Conclusion: In patients with CRS, BSIT scores strongly correlate with SIT scores; however, the BSIT underestimates olfactory dysfunction as defined by the suggested cut-point of ≤8. Increasing the cut-point to ≤9 increased the sensitivity and accuracy of the BSIT.