The diagnostic value of dopamine transporter imaging and olfactory testing in patients with parkinsonian syndromes

The problem with this study is the use of the B-SIT which is far more restricted than the UPSIT (12 items versus 40). Previous studies have shown comparable diagnostic accuracy between UPSIT and DaTSCAN, although one might perhaps expect imaging to perform better than objective smell testing. One needs to consider the costs here... UPSIT $25 and DaTSCAN over $1000. In my opinion both have a place in the clinical and research setting, and agree that in combination predictive value is likely to maximal...

J Neurol. 2015 Jun 30. [Epub ahead of print]

Georgiopoulos C, Davidsson A, Engström M, Larsson EM, Zachrisson H, Dizdar N.

Abstract

The aim of the study was to compare the efficacy of olfactory testing and presynaptic dopamine imaging in diagnosing Parkinson's disease (PD) and atypical parkinsonian syndromes (APS); to evaluate if the combination of these two diagnostic tools can improve their diagnostic value. A prospective investigation of 24 PD patients, 16 APS patients and 15 patients with non-parkinsonian syndromes was performed during an 18-month period. Single photon emission computed tomography with the presynaptic radioligand 123I-FP-CIT (DaTSCAN®) and olfactory testing with the Brief 12-item Smell Identification Test (B-SIT) were performed in all patients. DaTSCAN was analysed semi-quantitatively, by calculating two different striatal uptake ratios, and visually according to a predefined ranking scale. B-SIT score was significantly lower for PD patients, but not significantly different between APS and non-parkinsonism. The visual assessment of DaTSCAN had higher sensitivity, specificity and diagnostic accuracy compared to olfactory testing. Most PD patients (75 %) had visually predominant dopamine depletion in putamen, while most APS patients (56 %) had visually severe dopamine depletion both in putamen and in caudate nucleus. The combination of DaTSCAN and B-SIT led to a higher rate of correctly classified patients. Olfactory testing can distinguish PD from non-parkinsonism, but not PD from APS or APS from non-parkinsonism. DaTSCAN is more efficient than olfactory testing and can be valuable in differentiating PD from APS. However, combining olfactory testing and DaTSCAN imaging has a higher predictive value than these two methods separately.