How does measured olfactory function correlate with self-ratings of the sense of smell in patients with nasal polyposis?

Abstract

The objectives of this study were to investigate correlations, before and after surgery, between olfactory function self-ratings and measurements, and self-ratings of nasal obstruction and smell; and to establish cutoff points of self-rating scores for smell reduction in patients with nasal polyposis (NP). Prospective study. A total of 80 patients with NP (36 women, 44 men; aged 49 ± 4 years) were enrolled. Self-ratings (0- to 10-point scale) and measurements of olfactory function with standardized Sniffin' Sticks odor threshold and identification tests were assessed 1 day before surgery, and at 6 weeks (26-78 days) and 7 months (132-318 days) after surgery. Relationships were studied with Spearman correlation coefficients. Cutoff points of self-rating scores for olfactory deficit were established using the receiver operating characteristic curve. Overall, olfactory function self-ratings and measurements correlated strongly preoperatively (r = -0.66, P < .0001) and postoperatively (r = -0.67 at 6 weeks and -0.66 at 7 months, P < .0001). This relationship was better in patients with previous surgery. The correlation was weaker before surgery (r = -0.35, P = .01) than after in hyposmic/anosmic patients (r = -0.74, P < .0001 at 6 weeks and r = -0.73, P = .0002 at 7 months) and was not found in normosmic patients. Self-ratings of nasal patency and smell were not correlated when two complaints were dissociated. Cutoff points of self-rating scores for smell reduction were nine units preoperatively and five units postoperatively. Self-ratings and measurements of olfactory function correlated well before and after surgery in NP patients with olfactory deficits. Self-ratings were not reliable pre- and postoperatively in normosmic patients.