The Leicester semi-automated olfactory threshold test--a psychophysical olfactory test for the 21st century.

Objective: Develop a useful and cost-effective olfactometer for routine clinical use by providing a standardised threshold test for patients with olfactory disorders presenting in the ENT clinic.

Method Of Study: A prospective study of olfactory thresholds in 48 healthy volunteers on 2 consecutive occasions, undergoing quantitative testing with an olfactometer. Further studies of 10 subjects performing 20 tests and 100 subjects performing a single test were performed. An olfactometer was designed to deliver a semi-automated threshold test for an odour. It contains 8 logarithmic dilutions of an odour along with a control valve operated by software from a laptop computer. Common potential variables for olfactory threshold testing were considered including peak inspiratory flow rate. The odours used were phenethyl alcohol (PEA) and eucalyptol (EUC). Subjects were asked to perform 2 tests within 1 month of each other and the mean threshold score for each was calculated to derive a test-retest score.

Main Results: Consistent olfactory thresholds for PEA were achieved with a mean concentration of 10-4. Test-retest reliability score (r(x)) for the olfactometer was r(x) = 0.78 (95% CI 0.67 to 0.89).

Principal Conclusions: The Leicester Olfactometer provides a simple and cost-effective method of reliably assessing olfactory thresholds in the outpatient clinic.