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New Study Questions Usefulness of DaTscan for Parkinsonís Diagnosis
- May 03 2012
In 2011, the United States Food and Drug Administration approved the use of DaTscan for detecting images of the level of dopamine transporters in the brains of people with suspected parkinsonian syndromes. Now, a new study indicates that DaTscan is no more accurate in diagnosing Parkinson’s disease (PD) than a doctor who specializes in movement disorders, calling into question the clinical usefulness of the procedure.
To perform DaTscan, doctors inject people with a small amount of a radioactive contrast agent that binds to dopamine transporters in the person’s brain. Then, doctors use a machine called a single-photon emission computed tomography (SPECT) scanner to measure the amount and location of the contrast agent, or compound in the brain. Because people with PD have fewer neurons with dopamine transporters, their brains typically show lower amounts of the agent than do the brains of people without PD.
The results of a DaTscan can be used to help rule out other diseases that may have similar symptoms to Parkinson’s, such essential tremor, especially for individuals early in the course of their disease. However, there are several other diseases, such as multiple system atrophy (MSA), which can also produce a loss of dopamine in the brain. A DaTscan cannot differentiate between those diseases and Parkinson's.
Raúl de la Fuente-Fernández, M.D., at the Hospital A. Marcide in Spain wondered how DaTscan’s accuracy compares with a doctor’s diagnosis of PD. So he analyzed data from two clinical studies of DaTscan, one that involved people diagnosed by their doctors as having “possible” or “probable” PD, and another that involved people diagnosed with more advanced disease. Dr. Fuente-Fernández calculated the accuracy of DaTscan assuming that the clinical diagnosis was “truth,” and did the same calculations for the doctor’s diagnosis assuming that the DaTscan diagnosis was “truth.”
- In the study of early Parkinson’s, the overall accuracy of DaTscan was equal to that of the accuracy of a physician’s diagnosis: both were 84 percent.
- For people with more advanced PD, the overall accuracy of DaTscan was likewise identical to that of a physician’s diagnosis: both were 98 percent.
What Does It Mean?
Dr. Fuente-Fernández’s study suggests that DaTscan may be redundant to clinical diagnosis for detecting PD. The two approaches have mathematically identical accuracies for diagnosing PD, but DaTscan is much more expensive than a clinical examination. Also, DaTscan exposes people to small amounts of radiation, which can increase a person’s risk for developing cancer. Therefore, DaTscan may be helpful only in a small number of cases, for example, people without a clear clinical diagnosis who are contemplating an invasive procedure such as deep brain stimulation.
Neither DaTscan nor a doctor’s examination is perfect (gold standard) method for diagnosing PD. Both methods will occasionally miss actual cases of PD, while misdiagnosing other diseases that resemble PD. Only an autopsy can conclusively determine whether a person’s brain exhibits PD pathology. Therefore, further studies are needed to compare DaTscan and clinical diagnosis to autopsy findings as the “standard of truth.”
In the meantime, referral to a movement disorders specialist is indicated in complex conditions where a doctor is unsure of the diagnosis. DaTscans should be reserved for the rare cases where even the movement disorders specialist would like to receive additional data. DaTscans are FDA approved to distinguish between essential tremor and PD. If the medical question is different (e.g., is this PD or multiple system atrophy) then DaTscans may not be helpful.
How can you find a movement disorders specialist? Read our recent article on the topic.
Reference: la Fuente-Fernández, de, R. (2012). Role of DaTSCAN and clinical diagnosis in Parkinson disease. Neurology, 78(10), 696–701. doi:10.1212/WNL.0b013e318248e520
Source Date: May 03 2012