|Year : 2017 | Volume
| Issue : 2 | Page : 143-148
Olfactory function and its association with ABO blood group in adults: A cross-sectional study
Anuran Mukherjee, Abhishekh Basavarajegowda, KT Harichandrakumar
Department of Transfusion Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
|Date of Web Publication||11-Sep-2017|
Department of Transfusion Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry
Source of Support: None, Conflict of Interest: None
Background: The effect of blood group antigens in human olfactory performance has not been established yet. This study was designed to find out the association if any of blood groups ABO of a person with the olfactory performance by some simple standard established olfactory tests. Materials and Methods: Olfactory threshold testing and olfactory identification testing were performed using the standard “i-smell” test using the common household items such as asafoetida (heeng), camphor, cardamom, clove oil, cumin seeds, lemon, and Vicks. The results were compared to see for association with ABO blood groups. The statistical analysis was done using IBM SPSS Statistics for Windows, Version 21.0., 2013 (Armonk, NY; IBM Corp.). Results: Among the 329 individuals participated in the study who were age and sex matched, there was an equal representation of all ABO blood groups. There was no statistically significant difference between the ABO groups either with olfactory threshold testing or with olfactory identification testing. Conclusion: Blood group is not proximally associated with olfactory function of an individual. A more objective test which may include complex or invasive studies in controlled environment with bigger sample may be planned for.
Keywords: Blood groups, i-smell test, olfactory testing
|How to cite this article:|
Mukherjee A, Basavarajegowda A, Harichandrakumar K T. Olfactory function and its association with ABO blood group in adults: A cross-sectional study. Glob J Transfus Med 2017;2:143-8
|How to cite this URL:|
Mukherjee A, Basavarajegowda A, Harichandrakumar K T. Olfactory function and its association with ABO blood group in adults: A cross-sectional study. Glob J Transfus Med [serial online] 2017 [cited 2022 Sep 25];2:143-8. Available from: https://www.gjtmonline.com/text.asp?2017/2/2/143/214274
| Introduction|| |
Blood group antigens and their association with body function and disease have been the subject of research in quite long time. There are 34 blood group systems, each with their characteristic antigens. ABO system is one of the most important, clinically significant, and vastly studied systems. Along with their expression on red blood cells, ABO antigens are also highly expressed on the surface of a variety of human cells and tissues, including the epithelium, sensory neurons, platelets, and the vascular endothelium  and in various sites of the body in different phases of embryogenesis, especially in animals. The clinical significance of the ABO blood group system extends beyond transfusion medicine, and several reports have suggested an important involvement in the development of cardiovascular, oncological, and other diseases., Recent research has also carved out a role for ABO blood group antigens in neuroscience. In fact, these antigens have been implicated in the development of olfactory nerve connectivity. In 1985, Mollicone et al. described the expression of B and H antigens on primary sensory cells of the rat olfactory apparatus and inner ear. Five years after this early report, Villaroya et al. suggested a possible role of the A gene or a gene closely linked to the ABO locus in the differential susceptibility to experimental allergic encephalomyelitis in rabbits.
Olfactory system and its elaborate role in controlling various physiologic processes have been a mystery for many years. Several molecular factors and downstream signaling pathways are involved in recognizing odor from the external environment. Furthermore, the olfactory neurons project to various parts of the brain to generate appropriate response. Some studies show that the olfactory system of humans has a subsystem mode of organization, meaning as per the stimulus of odor, there are specific regions in the nasal cavity containing neurons that will get stimulated, and various molecules will be employed to generate electrical stimulus that will be matched as per various modes of neural coding and various other neural recognition mechanisms.
Of particular interest, in lower animals, carbohydrate antigens have been shown to be present in various parts of the olfactory system. Their function and role in controlling olfactory function need much more assessment. Studies have shown that H carbohydrate is expressed in sensory neurons in the main and accessory olfactory system while blood group A antigen expressed in vomeronasal organs. The vomeronasal organ has shown the presence of some taste receptors, particularly the bitter taste receptors.
Several molecular factors and an elaborate network of neurons are involved in this very process of olfaction. The odor molecules present in substances bind to G-protein-coupled receptors that lead to nerve depolarization in the olfactory rootlets that finally culminate in the brain lobe, more precisely the olfactory cortex, where signals are interpreted and the appropriate response is generated. However, apart from the conventional G-protein-coupled receptors, the olfactory rootlets and the neurons also express many other molecules, one of them being the ABO blood group antigens. In studies done in lower animals, it has been shown that blood group A antigen has been shown to regulate selective nerve fasciculation in regenerating olfactory accessory neurons. Furthermore, blood group H antigen has been shown to be present in both primary and olfactory sensory neurons. Such cell–cell interaction molecules that play a role in regulating fasciculation are thought to direct projection of the nerve to the target site, and hence, the absence or misexpression of such molecules affects convergence of neurons, giving rise to faulty response.
Since the role and the effect of blood group antigens in human olfactory performance need to be established yet, this study was designed to find out the association if any of blood groups ABO of a person with the olfactory performance by some simple standard established olfactory tests.
| Materials and Methods|| |
This study was conducted as an observational cross-sectional study. The study was carried out as pilot study as no previous data or study has been conducted in this arena. The study was conducted in the institute premises, mainly in the department of transfusion medicine based on the convenience of the study participants. It was conducted over a period of 2 months, after obtaining ethical approval by the Institute Ethics Committee.
Based on the prevalence of the least common ABO phenotype which is AB (around 5% in our population), sample size of 300 (75 in each blood group) was decided to be included in this study. However, a total of 329 participants, all above 18 years of age, participated in this study (75 belonging to A blood group, 80 B, 87 O, and 87 AB). In each group, the number of males and females was almost similar. The study population included faculty, students, and staff of the institute, as well as healthy voluntary blood donors, who were willing to take part in this study. Pregnant mothers were excluded from this study as pregnancy alters human olfactory function. Furthermore, morbid individuals were also excluded from this study., People who had rhinitis during the time of conducting the test were asked to take the test later after resolving the condition. People known to be allergic to any of the substance that was used in this study were proposed to be excluded though we did not have any.
Every participant was briefed of the study procedure and concerns if any was addressed. The study was conducted in a single-blinded manner, wherein the principal investigator performed the tests without having the knowledge of the blood group of the participant. The other investigator selected the participants after obtaining consent from them, and their blood group data were kept concealed from the person conducting the olfactory tests. Each participant was assigned a unique identification number. The blood group data of the participants were obtained from institute identity (ID) card for staff and students as the institute verifies the blood group of every new admission and recruitment by performing relevant testing in the blood bank as a part of filling up ID card information. For blood donors, the blood group data were confirmed by tube agglutination method.
The olfactory function of participants was assessed by two tests – the olfactory threshold test and the olfactory identification testing. The tests were conducted as per “i-smell” test, which used test reagents that were easily obtained and were easily identifiable by the individuals.
For olfactory threshold testing, eight dilutions of commercial rose water in distilled water were prepared. Rose water contains phenyl ethyl alcohol, which is selective to olfactory neuron, and it does not stimulate trigeminal neuron extensively., The concentration of the solutions ranged from 0.25%, 1%, 2%, 4%, 8%, 16%, 32%, and 64% (v/v). The solutions were kept in airtight bottles and were replaced every alternate day. The container was selected such that the diameter of its mouth was just adequate to be smelt clearly by one nostril.
For olfactory identification testing, seven commonly used household substances were used – asafoetida (heeng), camphor, cardamom, clove oil, cumin seeds, lemon, and Vicks. These were selected for this test based on cost, easy of availability, and more importantly the fact that these are commonly used substances in home, kitchen, and are likely to be identified easily. Furthermore, cardamom and cumin seeds were included in the test on consideration those they were part of “i-smell” test.
The tests were either performed on the same day or on the next day by the principal investigator. For people who had any upper respiratory tract infection, the tests were done only after their infection resolved. In case of females, the tests were done mostly on the second half of their menstrual cycle, to account for the changes in olfactory function with menstrual cycle.
The individuals were asked if they knew the smell of the substances that will be used in the test. If not, they were made familiar to the smell well in advance of doing the test. The tests were conducted only after the entire procedure was clear to the individual.
The individuals were blindfolded using black inert silk cloth. First, olfactory threshold test was performed. Each bottle containing rose water solution from the highest dilution to lowest was placed in front of each nostril, first left followed by the right, and the person was asked to gently sniff. This was alternated with a bottle containing normal saline solution as a control. The minimum concentration at which the person was able to detect the smell of rose water was taken as the olfactory threshold of the substance. Thirty-second time gap was given between testing two consecutive dilution bottles. Sufficient time interval was given before the next test was conducted as per the individual's convenience.
Next, olfactory identification test was performed. Seven opaque plastic boxes containing the aforementioned substances were used. The individual was blindfolded. Each container containing the substances was placed in front of the nose of the participant and was asked to gently smell and name the substance. The number of substances that were correctly identified by the individual was noted.
After the test was complete, the performance of the individual was told. The substances that were not able to be identified by the individual were shown to the individual after the test was completed. The signature of the individual was obtained.
The data were entered using redcap after creating an appropriate form. The statistical analysis was done using IBM SPSS Statistics for Windows, Version 21.0., 2013 (Armonk, NY, IBM Corp.).
| Results|| |
A total of 329 individuals participated in this study. About 26.4% of individuals had O and AB blood group in this study followed by 24.3% of patients with B blood group and 22.8% with A blood group. The majority of the patients (93.9%) are Rh positive and only few of them (6.1%) are Rh negative. The details are given in [Table 1].
|Table 1: Blood group-wise and sex-wise distribution of study participants (n=329)|
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The analysis is based on the association of olfactory threshold with ABO blood group and Rh type. AB blood type and olfactory threshold solution strength are not found to be statistically significantly associated (P > 0.05), which means smelling power in different solution strength is equally distributed in all the blood groups (P > 0.05). Rh type was not found to be significantly associated with solution strength (P > 0.05) as well. The details are given in [Table 2a] and [Table 2b], [Figure 1].
|Table 2a: Association of olfactory threshold with ABO blood group (n=329)|
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|Table 2b: Association of olfactory threshold testing with Rh type (n=329)|
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|Figure 1: Bar diagram showing the association of olfactory threshold value with ABO blood groups|
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The association of olfactory identification with ABO blood group is presented in [Table 3]. Regarding olfactory identification testing of asafoetida, 89.7% of the patients with AB group were able to detect its smell and 80% of A, B, and O blood group donors. However, this difference was not found to be statistically significant (P > 0.05), and this indicates that the asafoetida identification capacity is independent of ABO blood group. Camphor, clove oil cumin seeds, lemon, and Vicks are also not found to be significantly associated with ABO blood groups. However, in case of olfactory identification of cardamom, 70.7% are able to identify the smell of cardamom in Group A, 71.3% in Group B, 67.8% in Group O, and 89.47% in Group AB, and this difference was found to be significantly different between the ABO blood groups. The details can be inferred from [Table 3].
|Table 3: Association of olfactory identification with ABO blood group (n=329)|
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The association of olfactory identification function with Rh type is described in [Table 3] and [Figure 2]. Eighty-three percent are able to identify the smell of asafoetida in Rh positive and 80% in Rh negative. This difference was not found to be statistically significant (P > 0.05). Similarly, the olfactory identification of camphor, cardamom, clove oil, cumin seeds, and lemon was also not found to be significantly associated with Rh type. About 77.7% of participants were able to detect the Vicks smell in Rh positive and 55% in Rh negative, and this shows that a proportion of donors with Rh positive were able to detect the smell of Vicks more than the donor with Rh negative (P < 0.05). The details are given in [Table 4].
|Figure 2: Bar diagram showing number of people belonging to different blood groups who correctly identified each substance|
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|Table 4: Association of olfactory identification function with Rh type (n=329)|
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| Discussion|| |
The objective of this study was to observe if there is any association between olfactory function and the ABO blood group of a person. The association of Rh and olfactory function was also investigated. With regard to results obtained of olfactory threshold association with ABO blood group in adults, we found that there was no statistically significant finding. This can be explained due to multitude of factors. First, studies that have been done to investigate olfactory function and blood group association were done in animals using complex invasive procedures, whereas in our studies, we used simple noninvasive procedure to verify the hypothesis. Probably, ABO blood group antigens play a more distal role compared to the direct olfactory recognition pathways. Moreover, in animals, studies show that the blood group antigens are merely present in the olfactory neurons and their functional role in directly affecting the sense of olfaction need to be elaborately elicited. Furthermore, several confounding factors were not taken into account in the study like olfactory function variation with changes in hormonal status of an individual, the current mental status of the individual  to name a few.
With regard to results of olfactory identification tests with ABO blood group, we found that only in the identification of cardamom, statistically significant results were obtained. This is, however, irrelevant to the overall conclusion of the study. This is most probably an incidental result. As commonly household items were used for this test, more than 75% of people were able to identify each substance. However, no significant results relevant to research hypothesis can be concluded from this data, probably due to the same factors that were responsible for olfactory threshold results.
| Conclusion|| |
Based on the study carried out, we conclude that blood group is not proximally associated with olfactory function of an individual. A more objective test which may include complex or invasive studies in controlled environment with bigger sample may be thought of. However, this study opens the scope of further research of such nonhematological functions of blood group.
This study was conducted under the short-term studentship (STS) program of ICMR for the year 2016.
Financial support and sponsorship
This study was financially supported by ICMR STS 2016.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2a], [Table 2b], [Table 3], [Table 4]