The Correlation between the Results of the Sniffin' Sticks Test, Demographic Data, and Questionnaire of Olfactory Disorders in a Hungarian Population after a SARS-CoV-2 Infection

Abstract

Background: After a severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, smell disorders frequently occur, significantly affecting patients' quality of life (QoL).

Methods: 110 patients with persistent olfactory disorder after coronavirus infection were enrolled. These patients underwent chemosensory testing using the Sniffin' Sticks test, and completed the Questionnaire of Olfactory Disorders (QOD).

Results: 30% of the patients reported anosmia, and 70% reported hyposmia. Upon comparing subjective and chemosensory testing categories, good category matching was observed in 75.3% (i.e., anosmia based on both methods in 10 and hyposmia in 48 cases). Statistical analysis using the Chi-square test revealed a significant result (p = 0.001 *). Between the TDI (i.e., Threshold, Discrimination, Identification) results of the three subjective report groups (i.e., hyposmia, anosmia, and parosmia), no significant differences were observed. When the TDI and QOD results were compared, no consistent significant correlations were found in most TDI and QOD outcomes. Between the TDI and Scale 2 results, a significant, although slight correlation was observed by the Spearman's (rho = 0.213, p = 0.027 *) and Pearson's (rho = 0.201, p = 0.037 *) tests.

Conclusions: The nonsignificant correlation between objective and subjective methods suggests that these results should be interpreted independently. Moreover, adequate management is essential even in mild cases.

Keywords: SARS-CoV-2; Sniffin’ Sticks test; olfactory disorders; patient-reported outcome measures; quality of life.

Figure 1

Comparison between the TDI values according to gender. The boxes represent the middle 50% of the data, and the whiskers represent the upper and lower 25%. The black line inside the boxes represents the median value. Differences were analysed using the Mann–Whitney U test (p < 0.05 *). TDI = Threshold, Discrimination, Identification.

Figure 2

Correlation analysis between TDI and duration of symptoms and the participants’ age. Quadratic and linear regressions were used to analyse the relationship in the trends of the parameters (i.e., when age/duration is increasing, the TDI parameter is decreasing, or the contrary). The R²-values show the correlation coefficients, where a perfect correlation has an R²-value of 1. R² = coefficient of determination; TDI = Threshold, Discrimination, Identification.

Figure 3

Comparison between TDI scores and subjective categories reported by the patients. (1): Reference line for anosmia (showing 16). (2): Reference line for normosmia (showing 31). The boxes represent the middle 50% of the data and the whiskers the upper and lower 25%. The black line inside the boxes represents the median value. Differences were analysed using the Mann–Whitney U test (p < 0.05 *). TDI = Threshold, Discrimination, Identification.