The pyridine scale for clinical measurement of olfactory threshold: a quantitative reevaluation.

Serial dilutions of pyridine in water are employed for measuring the olfactory detection thresholds of patients. Experimental precautions are described that improve the precision and accuracy of the method. Existing data on the sensitivities of hyposmic patients are confirmed, but the sensitivities of normal subjects and of hyperosmic patients are believed to have been substantially overestimated in some earlier publications. Routine clinical applications of the revised pyridine odor threshold test are discussed. In the author's experience, the average cystic fibrosis patient is slightly hyposmic, and some cases of pituitary tumor are accompanied by a 100,000-fold hyperosmia.