Olfactory Threshold Test Research Articles

The Association Between Olfaction and Depression: A Systematic Review.

Previous studies on the relationship between olfaction and depression have revealed mixed results. In addition, few have focused on the reciprocity of this association. The aim of this study is to combine depression and olfactory data in two separate patient populations to further understand their association. A systematic literature review was conducted using 3 online databases to identify studies correlating olfaction and depression in patients presenting with either primary depression or primary olfactory dysfunction. For the depressed population, weighted means and standard deviations for the Sniffin' Sticks Test and the 40-item Smell Identification Test were combined using 10 studies. For the olfactory dysfunction population, weighted means of Beck's Depression Inventory were combined using 3 studies. Independent t-tests were used to compare differences between groups. Comparing primary depressed patients with controls, depressed patients showed decreased scores in olfactory threshold (6.31±1.38 vs. 6.78±0.88, P = 0.0005), discrimination (12.05±1.44 vs. 12.66±1.36, P = 0.0073), identification (12.57±0.74 vs. 12.98±0.90, P < 0.0001), and 40-Item Smell Identification Test (35.31±1.91 vs. 37.41±1.45, P < 0.0001). In patients with primary olfactory dysfunction, Beck's Depression Inventory scores were significantly different between patients classified as normosmics, hyposmics and anosmics (5.21±4.73 vs. 10.93±9.25 vs. 14.15±5.39, P ≤ 0.0274 for all 3 comparisons). In conclusion, patients with depression have reduced olfactory performance when compared with the healthy controls and conversely, patients with olfactory dysfunction, have symptoms of depression that worsen with severity of smell loss.

Chronic rhinosinusitis in adolescence is a rare but bothersome condition ‐ data from a Swedish population based cohort

Method We used 3112 16-year-olds from a Swedish birth cohort called BAMSE. The adolescents who fulfilled the criteria of CRS according to the European Position Paper on Rhinosinusitis (EPOS) in a questionnaire, was contacted by telephone to verify the diagnosis. Those with ongoing symptoms were invited for a clinical follow up with nasal endoscopy, olfactory threshold test (Sniffin’ sticks) and the disease specific quality-of-life (QoL) questionnaire SNOT22 (Sino Nasal Outcome Test 22). QoL was compared to those without CRS with the generic EQ-5D VAS.

The Evaluation of Olfactory Function in Patients With Schizophrenia.

The aim of this study was to compare olfactory threshold, smell identification, intensity and pleasantness ratings between patients with schizophrenia and healthy controls, and (2) to evaluate correlations between ratings of olfactory probes and illness characteristics. Thirty one patients with schizophrenia and 31 control subjects were assessed with the olfactory n-butanol threshold test, the Iran smell identification test (Ir-SIT), and the suprathreshold amyl acetate odor intensity and odor pleasantness rating test. All olfactory tasks were performed unirhinally.Patients with schizophrenia showed disrupted olfaction in all four measures. Longer duration of schizophrenia was associated with a larger impairment of olfactory threshold or microsmic range on the Ir-SIT (P = 0.04, P = 0.05, respectively). In patients with schizophrenia, female subjects’ ratings of pleasantness followed the same trend as control subjects, whereas male patients’ ratings showed an opposite trend. Patients exhibiting high positive score on the positive and negative syndrome scale (PANSS) performed better on the olfactory threshold test (r = 0.37, P = 0.04). The higher odor pleasantness ratings of patients were associated with presence of positive symptoms.The results suggest that both male and female patients with schizophrenia had difficulties on the olfactory threshold and smell identification tests, but appraisal of odor pleasantness was more disrupted in male patients.

Obese individuals have higher preference and sensitivity to odor of chocolate.

The worldwide epidemic of obesity has inspired a great deal of research into its causes and consequences. It is therefore surprising that so few studies have examined such a fundamental part of eating behavior: our sense of smell. The aim of the present study was to examine the differences in olfaction in obese and nonobese individuals. Participants (n = 40) categorized as obese (body mass index ≥ 30) or nonobese (body mass index < 30) completed a standardized olfactory threshold test to an ecologically valid food-related odor (chocolate), followed by a taste test. We found that compared with those not obese, obese individuals rated the chocolate odor as more pleasant and were substantially more sensitive to the odor. There was also evidence that their sense of taste was more acute for sour and salty tastants. Correlational analyses further revealed that those measures of olfaction and taste were positively associated with body mass index. These findings suggest that obese individuals show increased sensitivity and preference for an odor associated with energy dense foods. They also suggest that differences in our sense of smell offer a promising area for future research in obesity.

A pilot study of the Self-Administered Computerized Olfactory Testing System.

The Self-Administered Computerized Olfactory Testing System (SCOTS) was developed recently to perform the olfactory threshold test under computer control. The aim of this study was to evaluate the validity and test-retest reliability of the SCOTS. A total of 180 subjects were tested for olfactory thresholds using an odor detection threshold test and the SCOTS. There were 60 normosmic volunteers, 60 hyposmic patients, and 60 anosmic patients. Among them, 30 normosmic subjects were retested with the SCOTS at least 1 day after the first test occasion. The olfactory threshold test and retest results from the SCOTS were compared. The mean olfactory threshold attained from the SCOTS was -5.48 for normosmic subjects, -3.18 for hyposmic patients, and -2 for anosmic patients. The olfactory thresholds among the normosmic, hyposmic, and anosmic patients were significantly different (p < .001). The correlation coefficient between the olfactory thresholds of an odor detection threshold test and the SCOTS was 0.809 (p < .001). The test-retest correlation for the SCOTS-based olfactory thresholds was strong (r = 0.671; p < .001). Our results show that on the basis of its validity and test-retest reliability, the SCOTS was appropriate for self-administered tests of the olfactory threshold.

Evaluation of the olfactory bulb volume and olfactory threshold in patients with nasal polyps and impact of functional endoscopic sinus surgery: a longitudinal study.

Debate still persists on the relation between olfactory bulb volume (OBV) and olfactory function. Many studies suggest that olfactory deprivation decreases the OBV. The aim of this study was to compare the olfactory threshold and OBV of patients with nasal polyps to healthy individuals and to evaluate the impact of functional endoscopic sinus surgery (FESS) on OBV and olfactory threshold. A longitudinal study was carried out in Tehran between 2011 and 2012. Twenty-two patients with nasal polyps were compared with 37 healthy individuals. Olfactory threshold test and magnetic resonance imaging (MRI) were performed on all participants. Twenty-two patients in case group were followed for 6 months after FESS. OBV and olfactory threshold were measured after 6 months. There was no significant difference between the age, gender, and OBV of the 2 groups. However, the difference between olfactory threshold was significant (p = 0.005). The olfactory threshold showed no significant relation with OBV (p > 0.05). The correlation between Lund-Mackay score and the mean total OBV and left OBV was significant (r = -0.15, p = 0.045; r = -0.22, p = 0.047; respectively). The decrease in olfactory threshold measured after FESS was statistically significant. Right, left, and total OBV significantly increased after FESS. The results of our study show that FESS has a significant impact on OBV increment and olfactory threshold decrement. The olfactory bulb is a plastic structure and improvement in peripheral olfactory function results in increase in OBV. However, further studies are mandated, in order to establish this result.

Oxytocin administration selectively improves olfactory detection thresholds for lyral in patients with schizophrenia

Olfaction plays an important role in mammalian social behavior. Olfactory deficits are common in schizophrenia and correlate with negative symptoms and low social drive. Despite their prominence and possible clinical relevance, little is understood about the pathological mechanisms underlying olfactory deficits in schizophrenia and there are currently no effective treatments for these deficits. The prosocial neuropeptide oxytocin may affect the olfactory system when administered intranasally to humans and there is growing interest in its therapeutic potential in schizophrenia. To examine this model, we administered 40IU of oxytocin and placebo intranasally to 31 patients with a schizophrenia spectrum illness and 34 age-matched healthy control participants in a randomized, double-blind, placebo-controlled, cross-over study. On each test day, participants completed an olfactory detection threshold test for two different odors: (1) lyral, a synthetic fragrance compound for which patients with schizophrenia have specific olfactory detection threshold deficits, possibly related to decreased cyclic adenosine 3',5'-monophosphate (cAMP) signaling; and (2) anise, a compound for which olfactory detection thresholds change with menstrual cycle phase in women. On the placebo test day, patients with schizophrenia did not significantly differ from healthy controls in detection of either odor. We found that oxytocin administration significantly and selectively improved olfactory detection thresholds for lyral but not for anise in patients with schizophrenia. In contrast, oxytocin had no effect on detection of either odor in healthy controls. Our data indicate that oxytocin administration may ameliorate olfactory deficits in schizophrenia and suggest the effects of intranasal oxytocin may extend to influencing the olfactory system. Given that oxytocin has been found to increase cAMP signaling in vitro a possible mechanism for these effects is discussed.

Effect of Strong Fragrance on Olfactory Detection Thresholds of Health Workers at UCH Ibadan, Nigeria

Objectives: Assess the effect of perfume on olfactory detection thresholds of health workers at the University College Hospital, Ibadan. Methods: This was a quasi-experimental study on olfactory detection thresholds of one hundred healthy health workers in a tertiary health institution from September 2013-November 2013. A structured questionnaire was administered to participants 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 and thereafter had olfactory detection threshold testing done with varied concentrations of n-butanol in a forced triple response and staircase fashion. Olfactory detection thresholds at baseline and after exposure to Lynx perfume were determined and compared. Results: Thirty-seven males and 63 females were evaluated. Their ages ranged from 19-59 years with a mean age 31 years ± 8. Subjectively, 94% participants had excellent olfactory function. In the pre-exposure forced triple response, 88% participants were able to detect the odor at ≤0.25 mmol/L concentrations while in the post-exposure forced triple response, only 66% participants were able to detect the odor at ≤0.25 mmol/L concentrations. There was also a statistically significant difference in the olfactory detection threshold score between the pre-exposure and post-exposure period in the participants ( P &lt; .05). Conclusions: Use of fragrance affects the olfactory detection threshold. Therefore, wearers should be aware of this and its implications on test of olfaction.

Olfactory Bulb Volume in Nasal Polyposis

Objectives: There is still a debate about the relation of olfactory bulb volume (OBV) to olfactory function. Many studies suggest that olfactory deprivation decreases olfactory bulb volume. The aim of this study was to compare the olfactory threshold and olfactory bulb volume of patients with nasal polyps and healthy individuals. Methods: This was a case control study that was carried out in Valiasr hospital of Tehran University of Medical Sciences in 2010-2011. 22 patients with nasal polyps were compared with 37 healthy individuals. Olfactory threshold test and magnetic resonance imaging (MRI) were performed in all participants. Age, gender, left OBV, right OBV, total OBV, and olfactory threshold were recorded. Results: There was no significant difference between the age, gender, and olfactory bulb volume of patients of the two groups (P &gt; 0.05). However, the difference between olfactory threshold of the two groups was significant (P &lt; 0.0001). Also, olfactory function and threshold showed no significant relation with olfactory bulb volume (P &gt; 0.05). Conclusions: The results of this study show that MRI and OBV cannot be trusted in determining the olfactory function of patients with nasal polyps. However, further research needs to be done in order to establish this relationship. Also, considering the duration of olfactory dysfunction may be helpful in this research.

Intranasal Insulin Reduces Olfactory Sensitivity in Normosmic Humans

High densities of insulin receptors are found throughout the human brain, including the olfactory bulb, an essential brain area for odor processing. This brain region is the phylogenetically oldest part of the olfactory central nervous system. We hypothesized that enhanced brain insulin signaling would modulate olfactory processing in humans. We applied a double-blind, placebo-controlled, balanced within-subject design. This study was conducted in the research unit of a university hospital. INTERVENTIONS/PARTICIPANTS/MAIN OUTCOME MEASURES: A single dose of either insulin (40 IU) or placebo was intranasally administered to 17 normal-weight normosmic participants (7 women). Subjects' olfactory abilities were examined by means of an olfactory threshold test (odorant n-butanol) and an olfactory discrimination test. In addition, circulating concentrations of glucose, insulin, and cortisol levels were measured. After intranasal insulin administration, subjects' sensitivity for the odorant n-butanol was significantly decreased compared with that for the placebo condition (-13%; P = .025), whereas olfactory discrimination ability was not (P = .841). While serum insulin and serum cortisol were not altered after intranasal insulin administration, there was a small but significant drop in plasma glucose levels. Importantly, a correlational analysis demonstrated that this treatment-induced drop in plasma glucose was not related to the effects of intranasal insulin on olfactory sensitivity. These findings suggest that intranasal insulin impairs olfactory sensitivity for a nonfood odorant, whereas no such effects were found for olfactory discrimination. Thus, variations in brain insulin signaling most likely have implications for the olfactory threshold of normosmic humans. Bearing in mind the fact that insulin acts as an anorexigenic signal in the human brain, further studies are needed to test whether intranasal insulin also impairs the ability of humans to perceive food-related odors.

Olfactory Disorders in HIV Positive Patients

Objective: Chemosensory disorder in HIV-infected patients can lead to lack of intake and subsequently malnutrition, weight loss, and wasting. In this study we aimed to evaluate the prevalence and probable associated factors of olfactory disorder in HIV-positive patients. Method: This case-control study was conducted in Tehran, Imam Khomeini Hospital on 70 HIV-positive patients and 70 control subjects in 2011. Variables of age, gender, route of transmission, duration of infection, last CD4 count, opportunistic infection, drug history, HCV concurrent infection, patient’s self-evaluation of his own olfactory function, and threshold test were extracted and evaluated. Results: Male to female ratio in case and control groups was 0.89 and 1.69, respectively. Age was 43 ± 15 years and 35 ± 7 years in case and control groups, respectively. Case groups showed a significant lower result in threshold test scores, considering smoking cofounder effect. Independent variables of gender, antiretroviral therapy, and duration of infection have significant effect on threshold test scores. Conclusion: Olfactory threshold test disorders are common in HIV-positive patients. Age, gender, and smoking are probably effective on threshold test scores. CD4 count most likely does not have effect on threshold test. Recommendation on the effect of antiretroviral-therapy, duration of infection, route of transmission, opportunistic infection and HCV co-infection needs further investigations.

Applicability of the Cross-Culturally Modified University of Pennsylvania Smell Identification Test in a Japanese Population

The University of Pennsylvania Smell Identification Test (UPSIT) is a popular olfactory function test used throughout the world. In Japan, however, it is not widely used because it is written in English and some of the test odorants are unfamiliar to the Japanese population. Recently, a cross-culturally modified UPSIT was developed. This study was designed to determine if the Japanese version of the UPSIT (UPSIT-J) is effective in Japanese populations. We administered the UPSIT-J to 50 normosmic Japanese subjects and 54 Japanese patients with known olfactory dysfunction. Subjects were also administered the Japanese standard olfactory threshold test (T&T olfactometry), the Odor Stick Identification Test for Japanese (OSIT-J) and i.v. olfactometry (the Alinamin test). Test results from the UPSIT-J and subjects' opinions were compared with the standard Japanese tests of olfactory function. Most subjects reported that the UPSIT-J was easy and interesting compared with OSIT-J and easier and more interesting than the T&T olfactometry and Alinamin test. Identification rates for nine of the UPSIT-J odorants were found to be <80% for normal subjects. UPSIT-J scores correlated with subjects' self-reported levels of olfactory function (r(s) = 0.85), OSIT-J score (r(s) = 0.86), recognition threshold of the T&T olfactometry (r(s) = 0.80), and Alinamin test results (r(s) = 0.38 for latency; r(s) = 0.52 for duration time). Although a cultural bias was detected for some test odorants, this study indicates that the UPSIT-J is effective for use in the clinic to assess olfactory function in the Japanese population.

Olfactory function improves following hemodialysis

Olfactory function has been shown to be affected in chronic kidney disease; however, studies are contradictory and little is known on the effects of dialysis. To resolve these issues we tested olfactory function in 24 healthy controls and in 28 patients with chronic kidney disease receiving hemodialysis (20 patients) or peritoneal dialysis (the other 8). As assays for olfactory function we measured smell identification, n-butanol and acetic acid thresholds, Kt/V urea, percentage reduced urea, and weights before and after dialysis. Olfactory function was also self-rated by the participants. Compared to healthy controls, predialysis olfactory function was moderately but significantly decreased in the two dialysis groups, with hemodialysis patients being more affected. Patients self-rated olfactory function similar to that of healthy controls, suggesting that patients are unaware of the olfactory decrease. Olfactory function was significantly improved by one hemodialysis session. Neither body mass index, total volume loss, nor any other dialysis parameter correlated with olfactory function or its restitution following hemodialysis. The observed pattern of improvement suggests underlying mixed peripheral and central mechanisms. Thus, olfactory dysfunction in patients with chronic kidney disease is readily reversible by hemodialysis.

High Hunger State Increases Olfactory Sensitivity to Neutral but Not Food Odors

Understanding how hunger state relates to olfactory sensitivity has become more urgent due to their possible role in obesity. In 2 studies (within-subjects: n = 24, between-subjects: n = 40), participants were provided with lunch before (satiated state) or after (nonsatiated state) testing and completed a standardized olfactory threshold test to a neutral odor (Experiments 1 and 2) and discrimination test to a food odor (Experiment 2). Experiment 1 revealed that olfactory sensitivity was greater in the nonsatiated versus satiated state, with additionally increased sensitivity for the low body mass index (BMI) compared with high BMI group. Experiment 2 replicated this effect for neutral odors, but in the case of food odors, those in a satiated state had greater acuity. Additionally, whereas the high BMI group had higher acuity to food odors in the satiated versus nonsatiated state, no such differences were found for the low BMI group. The research here is the first to demonstrate how olfactory acuity changes as a function of hunger state and relatedness of odor to food and that BMI can predict differences in olfactory sensitivity.

Comparison of two different odorants in an olfactory detection threshold test of the Sniffin’ Sticks

The olfactory test battery Sniffin’ Sticks is a test of nasal chemosensory function that is based on pen-like devices for odour presentation. It consists of three olfactory subtests: threshold, discrimination, and identification. The detection threshold can be measured using two different odorants--n-butanol or PEA (phenylethyl alcohol). Both tasks are commonly applied in published studies, but little is known about the formal comparison of values obtained using them. Unlike the Sniffin’ Sticks with n-butanol as odorant, there is poor validation for the threshold subtest with the odorant PEA. The purpose of this study was to compare these two different odorants. Both odorants were applied to 100 normosmic, healthy subjects (50 females). The experiment was divided into two sessions performed on two different days. After each threshold test the discrimination and identification subtests were conducted. We obtained significant differences in detection thresholds of PEA and n-butanol. The mean score of PEA threshold and PEA TDI (sum of threshold, discrimination, identification) was significantly higher compared to n-butanol. No significant correlation between individual PEA and n-butanol thresholds was observed. The differences between both odorants indicate that a formal validation of the Sniffin’ Sticks with PEA as odorant for probing olfactory thresholds may be required.

Comparison of two different odorants in an olfactory detection threshold test of the Sniffin’ Sticks

The olfactory test battery Sniffin’ Sticks is a test of nasal chemosensory function that is based on pen-like devices for odour presentation. It consists of three olfactory subtests: threshold, discrimination, and identification. The detection threshold can be measured using two different odorants--n-butanol or PEA (phenylethyl alcohol). Both tasks are commonly applied in published studies, but little is known about the formal comparison of values obtained using them. Unlike the Sniffin’ Sticks with n-butanol as odorant, there is poor validation for the threshold subtest with the odorant PEA. The purpose of this study was to compare these two different odorants. Both odorants were applied to 100 normosmic, healthy subjects (50 females). The experiment was divided into two sessions performed on two different days. After each threshold test the discrimination and identification subtests were conducted. We obtained significant differences in detection thresholds of PEA and n-butanol. The mean score of PEA threshold and PEA TDI (sum of threshold, discrimination, identification) was significantly higher compared to n-butanol. No significant correlation between individual PEA and n-butanol thresholds was observed. The differences between both odorants indicate that a formal validation of the Sniffin’ Sticks with PEA as odorant for probing olfactory thresholds may be required.

Nasal functional modifications after physical exercise: olfactory threshold and peak nasal inspiratory flow

Statement of problem: The respiratory nasal effects of physical exercise have been extensively investigated; on the other hand there are no data regarding olfactory threshold modification after aerobic physical exercise. Methods: The present prospective study investigated the modifications in nasal respiratory flows and olfactory thresholds after controlled aerobic physical exercise in a cohort of 15 adult, healthy volunteers. The Peak Nasal Inspiratory Flow (PNIF), and the Sniffin’ Sticks olfactory threshold test were used for our determinations. Main results: The mean PNIF after physical exercise was significantly higher than the mean PNIF value found before physical exercise. Statistical analysis ruled out any significant difference between mean olfactory thresholds pre vs post physical exercise. Principal conclusions: These outcomes confirmed PNIF sensitivity and reliability also in determining the changes in nasal patency occurring after physical exercise. The active vasoconstriction of nasal mucosa associated with the reduction of blood flow to the olfactory epithelium due to physical exercise may be compensated for by the increase of olfactory molecules that reach the olfactory mucosa because of nasal mucosal shrinkage: this mechanism could explain the stability of mean olfactory threshold after physical exercise.

Nasal functional modifications after physical exercise: olfactory threshold and peak nasal inspiratory flow

The respiratory nasal effects of physical exercise have been extensively investigated; on the other hand there are no data regarding olfactory threshold modification after aerobic physical exercise. The present prospective study investigated the modifications in nasal respiratory flows and olfactory thresholds after controlled aerobic physical exercise in a cohort of 15 adult, healthy volunteers. The Peak Nasal Inspiratory Flow (PNIF), and the Sniffin’ Sticks olfactory threshold test were used for our determinations. The mean PNIF after physical exercise was significantly higher than the mean PNIF value found before physical exercise. Statistical analysis ruled out any significant difference between mean olfactory thresholds pre vs post physical exercise. These outcomes confirmed PNIF sensitivity and reliability also in determining the changes in nasal patency occurring after physical exercise. The active vasoconstriction of nasal mucosa associated with the reduction of blood flow to the olfactory epithelium due to physical exercise may be compensated for by the increase of olfactory molecules that reach the olfactory mucosa because of nasal mucosal shrinkage: this mechanism could explain the stability of mean olfactory threshold after physical exercise.

Endoscopic Sinus Surgery improves olfaction in nasal polyposis, a multi-center study

A positive effect of Endoscopic Sinus Surgery (ESS) as sole treatment on olfactory thresholds and sense of smell in patients with nasal polyposis has been questioned. The aim of this study was to test the hypothesis that ESS has a positive effect on sense of smell and olfactory threshold in nasal polyposis. Uncontrolled post-hoc analysis of a prospective study of 160 patients, > or = 18 years, with bilateral nasal polyps that underwent ESS to treat bilateral nasal polyposis. The effect of ESS was assessed with an olfactory threshold test, a diary score and a smell and taste score, pre-, and post-ESS. All three effect measures were improved from pre-ESS to post-ESS. Olfactory threshold increased from 0.0 pre-ESS to 3.0 (p < 0.001), two weeks after surgery, and the smell diary score decreased from 3.0 to 1.7 during the same period (p < 0.001), i.e. improvement. The smell and taste score increased from 1.0 pre-ESS to 2.0 post-ESS (p = 0.002). Overall, the results were similar for patients with and without previous surgery, as well as for men and women. ESS without concomitant medical therapy seems to improve both sense of smell and olfactory thresholds in patients with nasal polyposis in the short term.

The Leicester semi-automated olfactory threshold test--a psychophysical olfactory test for the 21st century

Develop a useful and cost-effective olfactometer for routine clinical use by providing a standardised threshold test for patients with olfactory disorders presenting in the ENT clinic. A prospective study of olfactory thresholds in 48 healthy volunteers on 2 consecutive occasions, undergoing quantitative testing with an olfactometer. Further studies of 10 subjects performing 20 tests and 100 subjects performing a single test were performed. An olfactometer was designed to deliver a semi-automated threshold test for an odour. It contains 8 logarithmic dilutions of an odour along with a control valve operated by software from a laptop computer. Common potential variables for olfactory threshold testing were considered including peak inspiratory flow rate. The odours used were phenethyl alcohol (PEA) and eucalyptol (EUC). Subjects were asked to perform 2 tests within 1 month of each other and the mean threshold score for each was calculated to derive a test-retest score. Consistent olfactory thresholds for PEA were achieved with a mean concentration of 10-4. Test-retest reliability score (r(x)) for the olfactometer was r(x) = 0.78 (95% CI 0.67 to 0.89). The Leicester Olfactometer provides a simple and cost-effective method of reliably assessing olfactory thresholds in the outpatient clinic.