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. 