Contribution of canine olfaction in the diagnostic strategy of intermediate and high-risk prostate cancer: a double-blind validation study.

PURPOSE: Prostate cancer diagnosis is confirmed with a prostate biopsy, which is invasive and unpleasant. Adding canine olfaction into the diagnostic protocol could help avoid unnecessary biopsies. This study aims to determine whether dogs can identify ISUP (International Society of Urological Pathology) > 2 prostate cancer. MATERIALS AND METHODS: This double-blind, prospective, validation study included men with suspected prostate cancer between November 2022 and April 2023 in France. They were classified into two groups according to their prostate biopsy results; cases (ISUP > 2) and controls (ISUP < 1 or negative). Seven dogs analyzed their urine. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for canine olfactory detection of ISUP ≥ 2 prostate cancer were measured and compared with that of prostate MRI versus prostate biopsy. RESULTS: The seven dogs analyzed 151 urine samples, 78 from the case group and 73 from the control group. The minimal and maximal observed values were 54% and 86% for sensitivity, and 69% and 88% for specificity. Five dogs had a sensitivity above 73% and six dogs had a specificity above 75%. The kappa coefficient quantifying agreement between the biopsy result and the MRI PI-RADS ≥ 3 was 0.17 [- 0.14; 0.17], 0.20 [0.02-0.33] for PI-RADS ≥ 4 and 0.64 [0.5-0.75] for canine olfaction meaning there is a substantial agreement between the biopsy result and canine olfaction. CONCLUSIONS: Based on this study, the non-invasive and safe canine olfaction technique seems reliable for diagnosing ISUP ≥ 2 prostate cancer. Combined with prostate MRI, it may improve the decision-making process when choosing to perform prostate biopsies.

Sniffer dogs can identify lung cancer patients from breath and urine samples.

BACKGROUND: Lung cancer is the most common oncological cause of death in the Western world. Early diagnosis is critical for successful treatment. However, no effective screening methods exist. A promising approach could be the use of volatile organic compounds as diagnostic biomarkers. To date there are several studies, in which dogs were trained to discriminate cancer samples from controls. In this study we evaluated the abilities of specifically trained dogs to distinguish samples derived from lung cancer patients of various tumor stages from matched healthy controls. METHODS: This single center, double-blind clinical trial was approved by the local ethics committee, project no FF20/2016. The dog was conditioned with urine and breath samples of 36 cancer patients and 150 controls; afterwards, further 246 patients were included: 41 lung cancer patients comprising all stages and 205 healthy controls. From each patient two breath and urine samples were collected and shock frozen. Only samples from new subjects were presented to the dog during study phase randomized, double-blinded. This resulted in a specific conditioned reaction pointing to the cancer sample. RESULTS: Using a combination of urine and breath samples, the dog correctly predicted 40 out of 41 cancer samples, corresponding to an overall detection rate of cancer samples of 97.6% (95% CI [87.1, 99.9%]). Using urine samples only the dog achieved a detection rate of 87.8% (95% CI [73.8, 95.9%]). With breath samples, the dog correctly identified cancer in 32 of 41 samples, resulting in a detection rate of 78% (95% CI [62.4, 89.4%]). CONCLUSIONS: It is known from current literature that breath and urine samples carry VOCs pointing to cancer growth. We conclude that olfactory detection of lung cancer by specifically trained dogs is highly suggestive to be a simple and non-invasive tool to detect lung cancer. To translate this approach into practice further target compounds need to be identified.

Quantitative vapor delivery for improved canine threshold testing.

The canine olfactory system is a highly efficient and intricate tool often exploited by humans for detection for its many attributes, including impressive sensitivity to trace analyte vapors. Canine detectors are often touted as having lower limits of detection, or olfactory detection threshold (ODT), than other field-relevant detection technologies; however, previous attempts to quantify canine ODTs have resulted in reported estimates spanning multiple orders of magnitude, even for the same analyte. A major contributor to these discrepancies is the vapor delivery method used for testing, where losses due to adsorption and dilution are often unaccounted for, and the presence of unattended compounds in the vapor stream due to carryover may go unnoticed. In this research, a trace vapor generator (TV-Gen) was used to deliver quantitatively accurate amounts of vapor reproducibly over time for canine testing. Analyte losses due to adsorption to surfaces in the flow path, dilution in the sniff port at the outlet, and analyte carryover were considered. Computational fluid dynamic (CFD) modeling was used to visualize analyte vapor spread throughout the port. CFD simulations revealed the need for a diffuser to encourage the diffusion of the analyte throughout the port. As a result, the modified vapor generator provides analyte air as a diffuse flow that is evenly distributed through the custom sampling orifice, as opposed to a narrow stream of air at the chosen concentration which exits directly into the environment. Laboratory validations were carried out for three analytes, amyl acetate, 2,4-dinitrotoluene (DNT), and methyl benzoate. A linear response across more than two orders of magnitude vapor concentration range was achieved for all analytes. These efforts will be applied in further research utilizing this TV-Gen vapor delivery system for canine ODT testing, eliminating many quantitative changes seen previously. Graphical abstract.

Scent dog identification of samples from COVID-19 patients - a pilot study.

BACKGROUND: As the COVID-19 pandemic continues to spread, early, ideally real-time, identification of SARS-CoV-2 infected individuals is pivotal in interrupting infection chains. Volatile organic compounds produced during respiratory infections can cause specific scent imprints, which can be detected by trained dogs with a high rate of precision. METHODS: Eight detection dogs were trained for 1 week to detect saliva or tracheobronchial secretions of SARS-CoV-2 infected patients in a randomised, double-blinded and controlled study. RESULTS: The dogs were able to discriminate between samples of infected (positive) and non-infected (negative) individuals with average diagnostic sensitivity of 82.63% (95% confidence interval [CI]: 82.02-83.24%) and specificity of 96.35% (95% CI: 96.31-96.39%). During the presentation of 1012 randomised samples, the dogs achieved an overall average detection rate of 94% (±3.4%) with 157 correct indications of positive, 792 correct rejections of negative, 33 incorrect indications of negative or incorrect rejections of 30 positive sample presentations. CONCLUSIONS: These preliminary findings indicate that trained detection dogs can identify respiratory secretion samples from hospitalised and clinically diseased SARS-CoV-2 infected individuals by discriminating between samples from SARS-CoV-2 infected patients and negative controls. This data may form the basis for the reliable screening method of SARS-CoV-2 infected people.

A detection dog for obstructive sleep apnea.

PURPOSE: We sought to assess whether a dog can be trained to distinguish obstructive sleep apnea patients from healthy controls based on the olfactory detection of urine. METHODS: Urine samples were collected from 23 adult male obstructive sleep apnea patients and from 20 voluntary adult male volunteers. Three dogs were trained through reinforced operant conditioning. RESULTS: Two of the three dogs correctly detected two thirds of obstructive sleep apnea patients (p < 0.000194 and p < 0.000003, respectively). CONCLUSIONS: We found that dogs can be trained to distinguish obstructive sleep apnea patients from healthy controls based on the smell of urine. Potentially, dogs could be utilized to identify novel biomarkers or possibly screen for obstructive sleep apnea.

Olfactory sensitivity for mold-associated odorants in CD-1 mice and spider monkeys.

Using operant conditioning procedures, we assessed the olfactory sensitivity of six CD-1 mice and three spider monkeys for mold-associated odorants. We found that with all eight stimuli, the mice detected concentrations as low as 0.1 ppm (parts per million), and with two of them individual animals even detected concentrations as low as 1 ppt (parts per trillion). The spider monkeys detected concentrations as low as 4 ppm with all eight stimuli, and with four of them individual animals even detected concentrations as low as 4 ppb (parts per billion). Between-species comparisons showed that with all eight odorants, the mice displayed significantly lower threshold values, that is, a higher sensitivity than the spider monkeys, but not than human subjects tested in previous studies. Analysis of odor structure-activity relationships showed that in both species, the type of oxygen-containing functional group and the presence versus absence of a double bond as well as the length of the carbon backbone of the odor stimuli had a systematic effect on detectability. We conclude that both mice and spider monkeys are clearly able to detect the presence of molds and thus to assess the palatability of potential food using the volatiles produced by molds during putrefaction.

Olfactory Sensitivity for the Mammalian Blood Odor Component Trans-4,5-epoxy-(E)-2-decenal in CD-1 Mice.

Using a conditioning paradigm and an automated olfactometer, we investigated the olfactory sensitivity of CD-1 mice for the mammalian blood odor component trans-4,5-epoxy-(E)-2-decenal. We found that two of the animals significantly discriminated concentrations down to 3.0 ppt (parts per trillion) from the solvent, and three animals even successfully detected dilutions as low as 0.3 ppt. Intraspecific comparisons between the olfactory detection thresholds obtained here with those obtained in earlier studies with other odorants show that mice are extraordinarily sensitive to this blood odor component. Interspecific comparisons of olfactory detection thresholds show that human subjects are even more sensitive to trans-4,5-epoxy-(E)-2-decenal than the mice tested here. Both intra- and inter-specific comparisons suggest that neither neuroanatomical properties such as the size of the olfactory epithelium, the total number of olfactory receptor neurons, or the size of olfactory brain structures, nor genetic properties such as the number of functional olfactory receptor genes or the proportion of functional relative to the total number of olfactory receptor genes allow us to reliably predict a species' olfactory sensitivity. In contrast, the results support the notion that the behavioral relevance of an odorant rather than neuroanatomical or genetic properties may determine a species' olfactory sensitivity.

Olfactory sensitivity and odor structure-activity relationships for aliphatic ketones in CD-1 mice.

Using a conditioning paradigm, the olfactory sensitivity of CD-1 mice for a homologous series of aliphatic 2-ketones (2-butanone to 2-nonanone) and several of their isomeric forms was investigated. With all 11 odorants, the animals significantly discriminated concentrations as low as 0.01 ppm (parts per million) from the solvent, and with two odorants (2-octanone and 5-nonanone), the best-scoring animals even detected concentrations as low as 3 ppt (parts per trillion). Analysis of odor structure-activity relationships showed that the correlation between olfactory detection thresholds of the mice for the 2-ketones and carbon chain length can best be described as a U-shaped function with the lowest threshold values at 2-octanone. Similarly, the correlation between olfactory sensitivity and carbon chain length of symmetrical ketones (3-pentanone to 6-undecanone) can best be described as a U-shaped function. In contrast, no significant correlation was found between olfactory detection thresholds of the mice and position of the functional carbonyl group attached to a C7 backbone. A comparison between the olfactory detection thresholds obtained here with those obtained in earlier studies suggests that mice are significantly more sensitive for 2-ketones than for n-carboxylic acids of the same carbon chain length. Across-species comparisons suggest that mice are significantly more sensitive for aliphatic ketones than squirrel monkeys and pigtail macaques, whereas the ranges of human olfactory detection threshold values overlap with those of the mice with seven of the 11 ketones tested. Further comparisons suggest that odor structure-activity relationships are both substance class and species specific.

Turning tryptophanase into odor-generating biosensors.

An odor-based sensor system that exploits the metabolic enzyme tryptophanase (TPase) as the key component is reported. This enzyme is able to convert an odorless substrate like S-methyl-L-cysteine or L-tryptophan into the odorous products methyl mercaptan or indole. To make a biosensor, TPase was biotinylated so that it could be coupled with a molecular recognition element, such as an antibody, to develop an ELISA-like assay. This method was used for the detection of an antibody present in nM concentrations by the human nose. TPase can also be combined with the enzyme pyridoxal kinase (PKase) for use in a coupled assay to detect adenosine 5'-triphosphate (ATP). When ATP is present in the low µM concentration range, the coupled enzymatic system generates an odor that is easily detectable by the human nose. Biotinylated TPase can be combined with various biotin-labeled molecular recognition elements, thereby enabling a broad range of applications for this odor-based reporting system.

Canine olfactory detection and its relevance for the medical identification of patients with COVID-19.

INTRODUCTION: The assessment of Volatile Organic Compounds (VOCs) in exhaled breath or sweat represents a potential non-invasive and rapid diagnostic tool for respiratory diseases. OBJECTIVE: To determine if trained dogs can reliably identify the odour associated with COVID19. METHODS: This is a monocentric prospective study carried out in the Emergency Department (ED) of a university hospital fromJulyto November 2021.Axillary sweat samples from all patients were collected bytwo trained health care professionals. The samples were collected in the form of sterile gauze swabs placed under the armpits for at least 4 h for each patient.Then, Tubes wereshiftedto the double-blind dog training centre for VOC detection by two individuals. RESULTS: Dogs were tested using a total of 129 axillary sweat samples; 69 of the 107 patients who tested positive for COVID-19 based on their odours had a positive PCR/Antigen test and 19 of the 22 patients who were tested negative for COVID-19 by the dogs had a negative PCR test. The sniffer dog infection detection method had a sensitivity of 95.83% and a specificity of 33.33%. The PPV was 64.49% and the NPVwas 86.36%. The measurement of the intensity of the connection between the two variables (disease/sign) was very strong (Q = 0.84). This link is statistically significant (X2 = 19.13) with a probability p ≤ 0.001. CONCLUSION: Overall, the use of trained detection dogs as a screening method for SARS-CoV-2 is an interesting avenue of research that warrants further exploration and validation.

Parameter Mapping Sonification of Human Olfactory Thresholds.

An objective of chemical ecology is to understand the chemical diversity across and within species, as well as the bioactivity of chemical compounds. We previously studied defensive volatiles from phytophagous insects that were subjected to parameter mapping sonification. The created sounds contained information about the repellent bioactivity of the volatiles, such as the repellence from the volatiles themselves when tested against live predators. Here, we applied a similar sonification process to data about human olfactory thresholds. Randomized mapping conditions were used and a peak sound pressure, Lpeak, was calculated from each audio file. The results indicate that Lpeak values were significantly correlated with the olfactory threshold values (e.g., rS = 0.72, t = 10.19, p < 0.001, Spearman rank-order correlation; standardized olfactory thresholds of 100 volatiles). Furthermore, multiple linear regressions used the olfactory threshold as a dependent variable. The regressions revealed that the molecular weight, the number of carbon and oxygen atoms, as well as the functional groups aldehyde, acid, and (remaining) double bond were significant determinants of the bioactivity, while the functional groups ester, ketone, and alcohol were not. We conclude that the presented sonification methodology that converts chemicals into sound data allows for the study of their bioactivities by integrating compound characteristics that are easily accessible.

Identification of volatile sulfur odorants emitted from ageing wastewater biosolids.

Volatile sulfur compounds (VSCs) are important sources of unpleasant odours in biosolid emissions. However, the study of VSCs may be limited by complications in their gas phase measurements due to reactivity, transformations and varying reported odour detection thresholds. A range of methods were used to quantitatively analyse VSCs in wastewater biosolid emissions. VSCs were identified in aged biosolid emissions by gas chromatography (GC) with a sulfur chemiluminescence detector (SCD) and mass spectrometry coupled with olfactory detection port (MS/O). In total, 10 VSC's were identified with two volatile organic sulfur compounds (VOSCs), allyl methyl sulfide and methyl propyl sulfide being reported for the first time in biosolid emissions. The emission patterns of different VSCs varied as the biosolids aged. Initially, the median concentrations of H2S, dimethyl sulfide (DMS), dimethyl trisulfide (DMTS), methanethiol (MeSH) and ethanethiol (EtSH) were orders of magnitude greater than their reported odour detection threshold, suggesting they would contribute to the odorous impact of the biosolids. The maximum H2S value was equal to 59.9 × 103 µg/m3 and was at least one magnitude higher compared to VOSCs, such as dimethyl disulfide (DMDS) (3.8×103 µg/m3), DMS (4.53 × 103 µg/m3), EtSH (2.83 × 103 µg/m3) and MeSH (3.25 × 103 µg/m3). Among the identified VSCs, H2S was the prominent odorant in terms of the magnitude and the frequency of detection, both initially as well as throughout storage. However, DMTS should be considered as a high priority or key odorant due to its odour activity value (OAV) and frequency of detection (sensorially detected in more than 75% of samples, with an OAVs higher than 1).

Dogs Detecting COVID-19 From Sweat and Saliva of Positive People: A Field Experience in Mexico.

Context: Molecular tests are useful in detecting COVID-19, but they are expensive in developing countries. COVID-19-sniffing dogs are an alternative due to their reported sensitivity (>80%) and specificity (>90%). However, most of the published evidence is experimental, and there is a need to determine the performance of the dogs in field conditions. Hence, we aimed to test the sensitivity and specificity of COVID-19-sniffing dogs in the field. Methods: We trained four dogs with sweat and three dogs with saliva of COVID-19-positive patients, respectively, for 4.5 months. The samples were obtained from a health center in Hermosillo, Sonora, with the restriction to spend 5 min per patient. We calculated sensitivity, specificity, and their 95% confidence intervals (CI). Results: Two sweat-sniffing dogs reached 76 and 80% sensitivity, with the 95% CI not overlapping the random value of 50%, and 75 and 88% specificity, with the 95% CI not overlapping the 50% value. The 95% CI of the sensitivity and specificity of the other two sweat dogs overlapped the 50% value. Two saliva-sniffing dogs had 70 and 78% sensitivity, and the 95% CI of their sensitivity and specificity did not overlap the 50% value. The 95% CI of the third dog's sensitivity and specificity overlapped the 50% value. Conclusion: Four of the six dogs were able to detect positive samples of patients with COVID-19, with sensitivity and specificity values significantly different from random in the field. We considered the performance of the dogs promising because it is reasonable to expect that with gauze exposed for a longer time to sweat and saliva of people with COVID-19, their detection capacity would improve. The target is to reach the sensitivity range requested by the World Health Organization for the performance of an antigen test (≥80% sensitivity, ≥97% specificity). If so, dogs could become important allies for the control of the COVID-19 pandemic, especially in developing countries.

Developing and Understanding Olfactory Evaluation of Boar Taint.

Trained expert panels are used routinely in boar taint research, with varying protocols for training of panelists and scoring methods. We describe a standardized process for training and scoring, to contribute to standardize the olfactory detection of boar taint. Three experiments are described in which we (1) evaluate the importance of training and the effect of the previous sample, (2) determine detection thresholds on strips and in fat for our panel, and (3) test priming panelists before boar taint evaluation. For the final evaluation of boar taint, we propose a consistent three-person evaluation scoring on a 0-4 scale using a final mean score of 0.5 as the cut-off for boar taint. This gave an optimal sensitivity of 0.81 and a specificity of 0.56 compared to chemical cut-offs. Even limited training proved useful, but priming assessors with strips did not improve the evaluation of fat samples. Detection thresholds were higher in fat compared to strips, except for indole. We recommend panelists to always smell a non-tainted control sample after a tainted one as a 'reset' mechanism, before continuing. For longitudinal studies, we additionally advise to set up an expert panel with a fixed number of assessors performing each evaluation in duplicate.

Correlation between regional brain volume and olfactory function in very mild amnestic patients.

BACKGROUND & AIMS: We aimed to determine neural correlates of olfactory detection and identification and analyze associations between cognitive function and olfactory identification or detection in very mild amnestic patients. METHODS: We recruited 70 patients with chief complaints of memory impairment diagnosed as amnestic mild cognitive impairment (MCI) or Alzheimer's disease (AD) with a clinical dementia rating of 0.5. Olfactory detection and identification were assessed using T&T olfactometry. A voxel-wise correlation analysis of gray matter volume and olfactometry scores was performed. We also analyzed correlations between neuropsychological results and olfactometry scores. RESULTS: A significant negative correlation was observed between detection scores and nucleus accumbens and left parahippocampal gyrus volumes and between identification scores and orbitofrontal, right frontal, and right anterior temporal cortex volumes (p < .001). No significant correlation existed between detection and cognitive assessment scores. Identification score was significantly correlated with the Alzheimer's Disease Assessment Scale-Cognitive Part word recall score (r = 0.305, p = .01). CONCLUSIONS: Olfactory detection and identification dysfunction were attributable to impairments in different regions in MCI and very early AD; the former was attributed to the olfactory circuit, while the latter to neocortices. The dysfunction of identification of olfactory information was associated with episodic memory in those patients.

Identification of 3-(trifluoromethyl)phenol as the malodorous compound in a pollution incident in the water supply in Catalonia (N.E. Spain).

A study of organic compounds that caused a serious taste and odor episode of water supply in two residential areas in Catalonia (N.E. Spain) was carried out. Sweet and paint/solvent odor were the main descriptors used by consumers. Some cases of sickness and nausea were also associated with drinking water consumption by the consumers. Closed-loop stripping analysis (CLSA) combined with sensory gas chromatography and gas chromatography mass spectrometry detection were used to study the problem. As a result, 3-(trifluoromethyl)phenol (CAS number 98-17-9) was for the first time identified as a responsible of an odor incident in drinking water. Concentration levels of this compound were up to 17,000 ng/L in groundwater and up to 600 ng/L in distributed water. Odor threshold in water for 3-(trifluoromethyl)phenol was determined as 13 ng/L (45 °C).

Assessing individual performance and maintaining breath sample integrity in biomedical detection dogs.

In empirical tests of biomedical detection dogs, exhaled breath samples are often used because breath contains volatile organic compounds that can signal metabolic states, infection, or disease. However, in studies that present dogs with breath samples, results show a notable degree of variability both between and within studies. Differing protocols for the collection and storage of exhaled breath samples may contribute to this observed variability. The goal of the current study was therefore to test whether there was a difference in the detectability of breath samples collected using silicone-coated versus uncoated cotton balls. This was tested in two experiments. In the first experiment, breath samples were prepared using both silicone-coated and uncoated cotton balls, which were then left exposed to the surrounding air. Four dogs' detection of the samples was tested using a cued, three alternative forced choice (3AFC) procedure at regular intervals up to two hours after the samples were prepared. The results of Experiment 1 showed that the dogs' performance was above chance and there was no significant difference in the dogs' detection of the breath samples across conditions. In the second experiment, a series of breath samples were prepared and stored for one, two, three, and four week periods. The same four dogs' ability to detect the breath samples was tested each week using the same cued 3AFC procedure. The results of Experiment 2 showed that when silicone-coated cotton balls were used, all four dogs could detect the breath samples at above chance levels after the samples were stored for three weeks, and two dogs could detect the samples that were stored for four weeks. When the dogs were tested on their ability to detect the breath samples prepared using uncoated cotton, two dogs' performance fell to below chance levels at one week of storage time, while the other two dogs could detect the breath samples at above chance levels after the samples were stored for four weeks. Taken together, the results of the two experiments illustrate that silicone-coated cotton balls do not improve detectability of breath samples within two hours, but can greatly improve the detectability of breath samples stored over longer periods of time. Since the use of silicone-coated cotton balls only improved the detectability of the breath samples for two of the four dogs, these results highlight the importance of examining individual differences in dogs' performance. Furthermore, we argue that, given the inherent differences in olfactory ability across dogs, widespread use of silicone-coated cotton balls for the collection of breath samples would increase the pool of testable dogs for biomedical detection studies and would decrease the degree of variability both within and between studies.

Assessment of olfactory detection thresholds in children with autism spectrum disorders using a pulse ejection system.

BACKGROUND: Atypical responsiveness to olfactory stimuli has been reported as the strongest predictor of social impairment in children with autism spectrum disorders (ASD). However, previous laboratory-based sensory psychophysical studies that have aimed to investigate olfactory sensitivity in children with ASD have produced inconsistent results. The methodology of these studies is limited by several factors, and more sophisticated approaches are required to produce consistent results. METHODS: We measured olfactory detection thresholds in children with ASD and typical development (TD) using a pulse ejection system-a newly developed methodology designed to resolve problems encountered in previous studies. The two odorants used as stimuli were isoamyl acetate and allyl caproate. RESULTS: Forty-three participants took part in this study: 23 (6 females, 17 males) children with ASD and 20 with TD (6 females, 14 males). Olfactory detection thresholds of children with ASD were significantly higher than those of TD children with both isoamyl acetate (2.85 ± 0.28 vs 1.57 ± 0.15; p < 0.001) and allyl caproate ( 3.30 ± 0.23 vs 1.17 ± 0.08; p < 0.001). CONCLUSIONS: We found impaired olfactory detection thresholds in children with ASD. Our results contribute to a better understanding of the olfactory abnormalities that children with ASD experience. Considering the role and effect that odors play in our daily lives, insensitivity to some odorants might have a tremendous impact on children with ASD. Future studies of olfactory processing in ASD may reveal important links between brain function, clinically relevant behavior, and treatment.

Spider monkeys (Ateles geoffroyi) are less sensitive to the odor of aliphatic ketones than to the odor of other classes of aliphatic compounds.

Aliphatic ketones are widely present in body-borne and food odors of primates. Therefore, we used an operant conditioning paradigm and determined olfactory detection thresholds in four spider monkeys for a homologous series of aliphatic 2-ketones (2-butanone to 2-nonanone) and two of their isomers (3- and 4-heptanone). We found that, with the exception of the two shortest-chained ketones, all animals detected concentrations <1 ppm (parts per million), and with five odorants individual animals even reached threshold values <0.1 ppm. Further, we found a significant correlation between olfactory sensitivity of the spider monkeys and carbon chain length of the 2-ketones which can best be described as a U-shaped function. In contrast, no significant correlation was found between olfactory sensitivity and position of the functional carbonyl group. Across-odorant and across-species comparisons revealed the following: spider monkeys are significantly less sensitive to the odors of aliphatic ketones than to the odor of other classes of aliphatic compounds (1-alcohols, n-aldehydes, n-acetic esters, and n-carboxylic acids) sharing the same carbon length. Spider monkeys do not differ significantly in their olfactory sensitivity for aliphatic ketones from squirrel monkeys and pigtail macaques, but are significantly less sensitive to these odorants compared to human subjects and mice. These findings support the notion that neuroanatomical and genetic properties do not allow for reliable predictions with regard to a species' olfactory sensitivity. Further, we conclude that the frequency of occurrence of a class of odorants in a species' chemical environment does not allow for reliable predictions of the species' olfactory sensitivity.

Effect of strong fragrance on olfactory detection threshold.

OBJECTIVE: To assess the olfactory threshold of healthy volunteers at the University College Hospital, Ibadan and to investigate the effect of perfume on their olfactory detection thresholds. STUDY DESIGN: A quasi-experimental study on olfactory detection thresholds of healthy volunteers from September 2013 to November 2013. SETTING: Tertiary health institution. SUBJECTS AND METHODS: A structured questionniare was administered to the participants in order to obtain information on sociodemographics, occupation, ability to perceive smell, use of perfume, effects of perfume on appetite and self-confidence, history of allergy, and previous nasal surgery. Participants subjectively rated their olfactory performance. Subsequently, they had olfactory detection threshold testing done at baseline and after exposure to perfume with varied concentrations of n-butanol in a forced triple response and staircase fashion. RESULTS: Healthy volunteers, 37 males and 63 females, were evaluated. Their ages ranged from 19 to 59 years with a mean of 31 years ± 8. Subjectively, 94% of the participants had excellent olfactory function. In the pre-exposure forced triple response, 88% were able to detect the odor at ≤.25 mmol/l concentration while in the post-exposure forced triple response, only 66% were able to detect the odor at ≤.25 mmol/l concentration. There is also a statistical significant difference in the olfactory detection threshold score between the pre-exposure and post-exposure period in the participants (P < .05). CONCLUSION: Use of strong fragrances affects the olfactory detection threshold. Therefore patients and clinicians should be aware of this and its effects on the outcome of test of olfaction.