***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Olfactory impairment is increasingly recognized as an early symptom in the development of Parkinson 's disease . Testing olfactory function is a non-invasive method but can be time-consuming which restricts its application in clinical setting s and epidemiological studies . Here , we investigate odor identification as a supportive diagnostic tool for Parkinson 's disease and estimate the performance of odor subsets to allow a more rapid testing of olfactory impairment . Methodology /Principal Findings Odor identification was assessed with 16 Sniffin ' sticks in 148 Parkinson patients and 148 healthy controls . Risks of olfactory impairment were estimated with proportional odds models . R and om forests were applied to classify Parkinson and non-Parkinson patients . Parkinson patients were rarely normosmic ( identification of more than 12 odors ; 16.8 % ) and identified on average seven odors whereas the reference group identified 12 odors and showed a higher prevalence of normosmy ( 31.1 % ) . Parkinson patients with rigidity dominance had a twofold greater prevalence of olfactory impairment . Disease severity was associated with impairment of odor identification ( per score point of the Hoehn and Yahr rating OR 1.87 , 95 % CI 1.26–2.77 ) . Age-related impairment of olfaction showed a steeper gradient in Parkinson patients . Coffee , peppermint , and anise showed the largest difference in odor identification between Parkinson patients and controls . R and om forests estimated a misclassification rate of 22.4 % when comparing Parkinson patients with healthy controls using all 16 odors . A similar rate ( 23.8 % ) was observed when only the three aforementioned odors were applied . Conclusions / Significance Our findings indicate that testing odor identification can be a supportive diagnostic tool for Parkinson 's disease . The application of only three odors performed well in discriminating Parkinson patients from controls , which can facilitate a wider application of this method as a point-of-care test Few detailed clinico-pathological correlations of Parkinson 's disease have been published . The pathological findings in 100 patients diagnosed prospect ively by a group of consultant neurologists as having idiopathic Parkinson 's disease are reported . Seventy six had nigral Lewy bodies , and in all of these Lewy bodies were also found in the cerebral cortex . In 24 cases without Lewy bodies , diagnoses included progressive supranuclear palsy , multiple system atrophy , Alzheimer 's disease , Alzheimer-type pathology , and basal ganglia vascular disease . The retrospective application of recommended diagnostic criteria improved the diagnostic accuracy to 82 % . These observations call into question current concepts of Parkinson 's disease as a single distinct morbid entity The Sniffin ' Sticks 12‐ identification test ( SIT‐12 ) is the most commonly applied Danish olfaction screening tool ; however , it has never been vali date d in a Danish population . The screening score depends on familiarity with descriptors , which is strongly influenced by linguistic and cultural factors , why validation is m and atory . This study aim ed to vali date the SIT‐12 in a Danish population OBJECTIVE To investigate whether a new clinical olfactory test , the Odor Stick Identification Test for Japanese ( OSIT-J ) , can be used to assess olfactory function cross-culturally in a US patient population . DESIGN Cross-sectional prospect i ve study . SETTING A university medical center otolaryngology clinic . PATIENTS Fifty US patients presenting with complaints of olfactory dysfunction from December 2004 to January 2006 . INTERVENTIONS Olfactory testing and patient interview . MAIN OUTCOME MEASURES Comparison of test results obtained with the OSIT-J , the Connecticut Chemosensory Clinical Research Center ( CCCRC ) olfactory function test , and patients ' self-reported level of olfactory function . Patients ' opinions regarding the 2 test methods were also recorded . RESULTS The mean + /- SD time required to administer the OSIT-J ( 8 + /- 1 minutes ) was shorter than that required for the st and ard CCCRC test ( 21 + /- 6 minutes ) . Significant Spearman rank correlations were found between the OSIT-J and CCCRC test scores ( r(s ) = 0.80 , P<.001 , n = 50 ) , and patients ' self-reported level of olfactory function ( r(s ) = 0.73 , P<.001 , n = 50 ) . Although 3 of the 13 odors used in the OSIT-J were not familiar to US subjects , patients reported that the OSIT-J was easier , more interesting , and the odors used more pleasant than the CCCRC test . CONCLUSIONS Olfactory function tests developed in different countries should be evaluated to determine if a cross-cultural bias exists among test odorants . Although a cultural bias was detected for a few odorants , this study demonstrates that a modified version of the OSIT-J can be used to assess olfactory function in US patients The study aim ed to compare olfactory function in idiopathic Parkinson 's disease ( IPD ) and nonidiopathic Parkinson 's syndrome ( PS ) . At their first visit 50 PS patients ( age 38 - 80 years ) received testing for odor threshold , olfactory discrimination and identification . All patients underwent extensive neurological diagnostics including PET scans . Patients were followed up for 6 - 12 months . Most of IPD patients were functionally anosmic ( n=19 ) , the remaining IPD patients had severe/moderate hyposmia ( n=18 ) . PS patients diagnosed with multiple system atrophy had less severe olfactory deficits ( 7 hyposmia , 1 normosmia ) . With the exception of 1 hyposmic patient , other PS patients had no olfactory deficits ( progressive supranuclear palsy , corticobasal degeneration , psychogenic PS , essential tremor ) . This study added to previous findings : ( 1 ) there was no major difference betwesen olfactory function in IPD subtypes ; ( 2 ) all olfactory tests differentiated IPD from nonIPD . These data suggest that olfactory probes improve the diagnostic armamentarium in IPD The aim of this study was to determine whether extended olfactory testing within a single olfactory task and /or across olfactory tasks increases diagnostic accuracy of olfactory testing in Parkinson 's disease ( PD ) . Olfactory function was assessed using an extended version of the " Sniffin ' Sticks " , comprising 32-item odor identification and discrimination tasks , and a detection threshold task in 52 PD patients and 50 controls , all aged between 49 and 78 years .  ROC curves based on sensitivity and specificity estimates were used to compare the diagnostic accuracy of extended and combined olfactory testing . There was no significant difference in diagnostic accuracy between the 16-item and the 32-item versions of the odor identification or discrimination test . The single olfactory test that was best in discriminating between PD patients and controls was a 16-item odor identification test . A combination of the 16-item identification test and the detection threshold task had a significantly higher area under the curve than the 16-item odor identification test alone . In conclusion , extended testing across , and not within , olfactory tasks increases diagnostic accuracy of olfactory testing in PD . A combination of an odor detection threshold task and a 16-item odor identification test had the highest sensitivity and specificity in distinguishing between PD patients and controls Previous studies suggested that olfaction is normal in progressive supranuclear palsy ( PSP ) . We applied the University of Pennsylvania Smell Identification Test ( UPSIT ) to 36 patients with PSP who scored more than 18 on the  Mini Mental State Examination ( MMSE ) , 140 patients with nondemented Parkinson 's disease ( PD ) and 126 controls .  Mean UPSIT scores in PSP were lower than in controls ( P < 0.001 ) but higher than in PD ( P < 0.001 ) after adjusting for age , gender , and smoking history . For patients with PSP , UPSIT scores correlated with MMSE ( r = 0.44 , P = 0.006 ) but not disease duration ( P = 0.6 ) , motor subscale of the Unified Parkinson 's Disease Rating Scale ( P = 0.2 ) , or Frontal Assessment Battery ( P = 0.5 ) . The brains of six of the patients with PSP were examined postmortem and all revealed neurofibrillary tangles and tau accumulation in the rhinencephalon , although only three had hyposmia . Further prospect i ve studies including patients with early PSP and PSP-P with postmortem confirmation might help clarify if smell tests could be useful when the differential diagnosis lies between PD and PSP 
    Output:
    
Olfactory test can be a valuable ancillary tool in the diagnostic process in PD .
In a clinical setting , the identification part from Sniffin ' Sticks 16 is the most usable because it may be conducted quickly and independently of disease duration and severity .