From ""Rapid Clinical Evaluation of Anosmia - The Alcohol Sniff Test" (https://jamanetwork.com/journals/jamaotolaryngology/article-...):"Standard 70% isopropyl alcohol preparation pad is opened such that 0.5 cm of the pad itself is visible. The alcohol pad is placed beneath the patient's nostrils while the patient inspires twice, to familiarize himself or herself with the alcohol odor, and the subject is asked if he or she detects an odor. Odor thresholds for alcohols are 2 or more orders of magnitude lower than trigeminal thresholds for the same stimuli.6 Thus, an anosmic will detect the presence of alcohol trigeminally only when it is extremely close to the nose. The alcohol pad is withdrawn and the threshold test begun. The subject is asked to close the mouth and eyes, breathe normally, and indicate when the odor is detected. Active sniffing and deep inspiration are discouraged. The basic procedure follows the method of limits. A standard metric tape measure is extended downward from the patient's nares and held in place (Figure I ). The alcohol pad is placed 30 cm below the nose and, with each expiration, is moved 1 cm closer to the nares until the subject detects the presence of odor. The distance from the anterior nares to the alcohol padis measured in centimeters at the point at which the subject first detects the odor. The procedure is repeated 4 times and the mean distance defines the threshold.Butanol ThresholdFor purposes of comparison, all of the subjects completed a standard olfactory threshold test. A series of 10 concentrations of butanol ( -butyl alcohol) was used to determine absolute olfactory threshold sensitivity. The highest butanol concentration consisted of 4% vol/vol in distilled water. Each successive dilution was one third of the preceding dilution. Two "blanks," containing only distilled water, were also prepared. All bottles, including blanks, contained 60 mL of liquid. Olfactory threshold was assessed with a modified version7 of a 2-alternative, forced-choice,ascending method of limits procedure.8 The subject was presented with 2 bottles, one containing the odorant and the other consisting of distilled water. Each nostril was tested separately. The spout of the bottle was inserted into the nos tril of interest. The subject was asked to squeeze the bottleto generate a puff of air. The subject did this with both bottles. Subjects were asked to identify which of the 2 bottles contained the stronger odor.All subjects began at the lowest concentration to avoidadaptation.9 Incorrect choices led to presentation of a higher concentration and correct choices led to continued presentation of the same concentration to a criterion of 5 successive correct responses. The presentation of the odorantand blank were randomized for each comparison trial and the nostril to be tested first was also randomly determined. There were approximately 45 seconds between trials to allow time for recovery of the olfactory system and for the odor molecules to collect in the head space of the bottle."

However, this test has been called imprecise (https://journals.sagepub.com/doi/abs/10.2500/ajra.2017.31.44...).

If the paper is true, one could do spot checks today to estimate the true IFR in every country tomorrow on a shoestring budget.

https://www.statnews.com/2020/03/17/a-fiasco-in-the-making-a...

Depending on the results that might save trillions of dollars.