Odor test for autism diagnosis

Researchers determine autism based on the odor reaction
As a result of impaired sensorimotor coordination, autistic children do not exhibit the usual defensive reaction to the perception of unpleasant odors. They continue to breathe deeply, instead of reflexively slowing their breathing, says the Israeli research team around Liron Rozenkrantz of the Weizmann Institute of Science in the journal "Current Biology". A simple odor test could therefore facilitate the diagnosis of autism significantly in the future.

According to the researchers, the reaction to odors in the current studies has proven to be a relatively reliable indicator of autistic disorders. In their study, the scientists used the odor reaction to determine with more than 80% certainty whether a child was suffering from autism. In addition, the extent of the lack of defense reaction was related to the severity of the disease. The more pronounced the autistic disturbances were, the longer the children breathed the unpleasant odors in the experiment. In practice, the test could significantly simplify the diagnosis of autism.

With the help of the smell test, autism could be determined in early childhood. (Image: S.Kobold / fotolia.com)

Odor test with rotten fish and spoiled milk
The Israeli researchers of the Weizmann Institute have taken a closer look at the sense of smell in 18 healthy children and 18 autistic children. The mean age of the subjects was seven years. The scientists connected the children to a special device, where two nasal cannulae can be used to blow various odors into the nose while at the same time measuring nasal breathing. The children were then exposed to pleasant odors of roses and shampoo and unpleasant odors of sour milk and rotten fish. Normal is here an odor reaction in which pleasant odors are deeply inhaled and unpleasant odors cause a knee-jerk reduction of the breathing volume. Within ten minutes, the children were confronted with 20 different smells (10 pleasant / 10 uncomfortable) while the scientists observed how the tidal volume, peak air flow rate, air flow rate and duration of sniffing were.

Lack of defense reaction in autistic children
The observation of the four parameters had a significant interaction with the perfume value (pleasant to unpleasant) in the healthy subjects, which is evaluated as a normal odor reaction, the researchers report. The children had shown a corresponding reaction to the odorant properties within 305 milliseconds. In the case of autistic children, however, no comparable reaction was observed. They showed significantly less difference between the reaction to unpleasant and pleasant odors. Instead of stopping at the stench of rotten fish, the autistic children continued to take a deep breath. In addition, the researchers observed a correlation between the extent of the lack of defense response and the severity of the autistic disorder. The longer the subjects also inhaled the unpleasant odors normally, the more the impairments of social communication had turned out. According to their own information, the researchers were unable to establish a comparable relationship with motor skills.

Test independent of language ability
According to the scientists, the differences between the autistic children and the healthy children were so pronounced that it was possible to determine whether a child was suffering from autism on the basis of the odor test alone with an 81% certainty. The diagnostic possibilities could be significantly improved with the help of the test in her opinion, especially since this is not influenced by the language ability of the children. The scientists see the cause of the lack of odor reaction in autistic children in the "limited sensorimotor coordination." The control of breathing in unpleasant and pleasant odors is a highly complex procedure that will be permanently impaired in autistic disorders. In addition, the altered sense of smell in turn contributes to an impairment of social communication, so the researchers hypothesis. Therefore, the extent of the lack of odor reaction "predictive of impaired social communication, but not for generalized motor impairment."

Smelling test could make the autism diagnosis much easier
According to the researchers, the development of an appropriate odor test could make the diagnosis of autism much easier in the future, but further investigations would be necessary to clear up existing uncertainties. For example, it remains unclear whether this indicator is specific to autism or also occurs in other developmental disorders. Also, the sample in the current study was too small to be able to make clear statements here. Last but not least, some technical issues need to be resolved before the test can be a useful tool in everyday clinical practice, write Liron Rozenkrantz and colleagues. In the end, with his help, however, autism may be diagnosed relatively reliably - even in toddlers - within about ten minutes. (Fp)