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problems in quality of life were reported primarily in the areas of eating and safety [ 14 ] .
the major causes of olfactory disorders are head injury , infections of upper respiratory tract , sinonasal diseases , head trauma , and toxic exposure .
approximately 5% of the general population is anosmic ( no sense of smell ) , but about 15% have reduced olfactory function [ 58 ] .
a significant number of patients complain of a reduction in their olfactory function , so it becomes important to use appropriate diagnostic tools ( e.g. , the university of pennsylvania upsit smell identification test , 
quantitative smell disorders such as anosmia or hyposmia can be differentiated from normal olfactory function .
the  sniffin sticks  test was initially developed and validated on large numbers of patients in germany .
currently , the kit is used by many clinicians around the world and has been validated in various countries and populations ( e.g. , australia , greece , taiwan [ 1719 ] , italy , holland , sri lanka , and brazil ) .
the  sniffin sticks  test has been validated and normative data published on a large number of subjects in northern europe and smaller studies have proven its usefulness in assessing olfaction in populations around the world , but there is only 1 study evaluating the 
sniffin sticks  olfactory test in turkey . in that study researchers found quite poor scores in a turkish population when compared to other worldwide studies .
another goal of this study was to compare the scores of subjects with and without a complaint of olfactory dysfunction for detecting the clinical applicability of the 
this study was approved by the institutional review board of gulhane military medicine academy ( gata ) haydarpasa training hospital .
the study was conducted in otorhinolaryngology and neurology clinics of gata haydarpasa training hospital and istanbul surgery hospital and included 51 patients complaining of a reduction in their olfactory function ( abnormal group ) .
a group of 123 subjects who stated they have normal olfactory function were also enrolled ( healthy group ) .
no signs of nasal polyposis , marked septal deviation , or rhinosinusitis were found by endoscopic nasal examination in any of the subjects .
olfactory testing used 3 tests : tests for odor threshold ( testing by means of a single staircase procedure ) , odor discrimination ( 3-alternative forced choice ) , and odor identification ( 4-alternative forced choice ) .
for odor presentation , the pen cap was removed by the experimenter for approximately 3 seconds and the tip of the pen was placed approximately 12 cm in front of the nostrils . instead of liquid dye , the tampon of the pens for threshold testing was filled with phenyl ethyl alcohol ( pea , a rose - like odor ) diluted in propylene glycol ( dilution ratio 1 : 2 , starting at 4% ) .
odors were presented in a total of 16 triplets of pens , 1 containing diluted phenyl ethyl alcohol and 2 containing only propylene glycol ( negative controls ) .
the interval between presentations of individual pens of a triplet was approximately 3 seconds and presentation of the triplets to a subject occurred every 20 seconds . employing a 3-alternative , temporal forced choice paradigm , the subjects had to identify the pen that contained the odorant .
were blindfolded to prevent visual identification of the odor - containing pens . thresholds ( t ) were determined using a single - staircase technique . in the present 3-alternative , temporal forced - choice paradigm , 2 successive correct identifications of the pen containing the odor or 1 incorrect identification triggered a reversal of the staircase to the next higher or the next lower dilution step , respectively .
assessment of odor threshold was followed by a test of odor discrimination . for odor discrimination ( d ) , 16 triplets of pens were presented , with 2 containing the same odorant and 1 containing the target odorant .
the subjects task was to identify the sample that had a different smell . to prevent visual detection of the target pen
the final step a test of odor identification was performed to completely assess the subjects objective function .
odor identification ( i ) was assessed by means of 16 common odors . using a multiple forced - choice paradigm , identification of individual odors
each odorant was presented by the experimenter and there was an interval of at least 30 seconds to prevent olfactory desensitization .
subjects were free to sample the odors as often as necessary to make a decision .
overall olfactory function is expressed as the sum of the scores from the 3 individual tests ( tdi score ) .
data analysis was performed by spss 21.0 ( statistical package for social sciences , spss inc .
demographic data of the subjects were compared by t test or chi - squared test , as appropriate . to explore general olfactory sensitivity ( tdi score ) in relation to age and sex ,
data were submitted to analysis of variance ( anova ) using the general linear model with between subject factors ?
data analysis was performed by spss 21.0 ( statistical package for social sciences , spss inc .
chicago , il ) . the normal distribution of considered variables was evaluated using the shapiro - wilk test .
demographic data of the subjects were compared by t test or chi - squared test , as appropriate . to explore general olfactory sensitivity ( tdi score ) in relation to age and sex ,
data were submitted to analysis of variance ( anova ) using the general linear model with between subject factors ?
the participants were divided into 2 groups according to subjective olfactory function , either healthy or abnormal .
most participants ( 68% ) had a high educational level ( high school or university ) and there was no difference between the groups in terms of education and age ; however , there was significant difference in terms of sex .
table 1 summarizes the characteristics of each of the variables of interest by disease status .
differences in tdi , t , d , and i were significant between the abnormal and healthy groups .
descriptive statistics of normative values obtained in healthy subjects are shown in table 2 . when all the age groups were considered together in healthy subjects , the 10 percentiles of odor threshold score , odor discrimination score , odor identification score , and tdi score were 7.25 , 12 , 11 , and 32 , respectively .
anova testing did not reveal a significant effect of age on t , d , or tdi scores but a significant decrease was detected in i scores in subjects over the age of 55 ( p=0.04 ) .
a significant effect of subject sex was found in the i score ( p=0.03 ) and tdi score ( p=0.02 ) , with females being more sensitive than males . in the healthy group ,
peppermint , rose , fish , banana , cloves , garlic , and coffee were the odorants most reliably identified correctly , while turpentine , apple , leather , lemon , and liquorice were most commonly mistaken ( figure 1 ) . in the abnormal group , as expected , a larger proportion of subjects wrongly identified odorants ( figure 2 ) .
considering the 2 groups together , apple and turpentine were the least well - recognized odors from the 16 presented .
also , the present study validated that the  sniffin sticks  olfactory test is suitable for clinical usage in turkish populations . 
sniffin sticks  is a modern olfactory test recommended by the german olfactology and gustology association as a standard for olfactory testing .
however , cultural differences make the application of the odor identification tests in different countries difficult , because odor identification is strongly dependent on familiarity with the odors tested . when applied cross - culturally , the  sniffin sticks  test appears to perform well , but in some populations the test required adaptation using different distracters in the 4 alternative forced multiple - choice identification subtest [ 1619 ] . in a validating study conducted in taiwan , although the odorants were kept the same , some descriptors were changed from the original version . the authors concluded that the  sniffin sticks  test appears to be suited for the assessment of olfactory identification in an asian population after revision of the descriptors .
the authors did not encounter any problematic items in the identification list and found the 
the other , larger , study showed decreased identification ( < 70% ) for 6 of the odorants : aniseed , turpentine , liquorice , apple , lemon , and cinnamon .
the modifications in the list of descriptors after linguistic changes significantly increased the identification of problematic items .
translation and cultural adaptation of the descriptor list in the identification subtest was used in studies conducted in brazil , sri - lanka , and the netherlands , with the test being validated against normative data from germany [ 2123 ] . in a randomized crossover study on patients with hyposmia and anosmia ,
patients with hyposmia performed better in the contrasted test in odor identification , but patients with anosmia did not .
it appears that the use of more contrasted distracters can contribute to better discrimination between patients with hyposmia and anosmia , which is important in a clinical context . in our turkish population ,
the odors most commonly mistaken in the healthy group were turpentine ( 54% ) , apple ( 25% ) , lemon ( 21% ) , liquorice ( 21% ) , and pineapple ( 17% ) . in the abnormal group , the most commonly mistaken odorants were apple ( 72% ) , cinnamon ( 67% ) , turpentine ( 63% ) , pineapple ( 55% ) and liquorice ( 55% )
. a possible explanation for these results could be the similarity of distracters with the odorant , as in the case of apple ( distracters are orange , peach , and melon ) , cinnamon ( distracters are honey , vanilla , and chocolate ) and lemon ( distracters are grapefruit , apple , and peach ) or unfamiliarity with an odorant such as turpentine , liquorice , and pineapple . another possible reason for the difficulties in identification could lie in the odor itself : the currently used apple odor smells like granny smith apple and the participants confused this odor with air freshener . in turkish culture , people are accustomed to more sugary and sweet apple types . also , some of the odors presented as distracters may not be very familiar to turkish populations , for example ham , wine , rum , or gummy bears . according to hummel et al .
, a criterion for the selection of odorants was the successful identification of individual odorants from a list of 4 descriptors should be > 75% in healthy subjects . based on this view
our study had a limitation due to the low number of participants over the age 55 .
thus , further studies with a higher number of participants including all age groups are needed for the turkish population .
these results provide the basis for routine clinical evaluation of patients with olfactory disorders using the  sniffin sticks  test in turkish populations .
backgroundolfactory assessment is often neglected in clinical practice , although olfactory loss can assist in diagnosis and may lead to significant morbidity .  
 sniffin sticks  is a modern test of nasal chemosensory performance that was developed in germany and validated in many countries . 
 our aim was to validate the applicability of  
 sniffin sticks  in a turkish population.material/methodsthe study included 123 healthy volunteers with a reported normal sense of smell and 51 patients complaining of a reduction in their olfactory function presenting either at rhinology or neurology clinics . 
 the mean age of the subjects tested was 30.212.5 years in 126 males and 48 females . 
 the participants were divided into 2 groups according to subjective olfactory function  
 healthy or abnormal . 
 each subject s olfactory function was assessed using the  
 sniffin sticks  
 test.resultswe found significant differences in  
 sniffin sticks  test results between the abnormal and healthy groups . in healthy subjects , 
 the 10th percentiles of odor threshold score , odor discrimination score , odor identification score , and tdi score were 7.25 , 12 , 11 , and 32 , respectively . 
 considering the 2 groups together , apple and turpentine were the least well - recognized odors from the 16 odors presented.conclusionsour study provides an update of normative values for routine clinical use of  
 sniffin sticks  in a turkish population . 
 also , the present study validates that  
 sniffin sticks  olfactory test was applicable for clinical usage in a turkish population .