Three-step risk-screening method devised for Parkinson’s disease

By Andrew Czyzewski, MedWire Reporter

Researchers have proposed a three-step screening battery to identify people at risk for developing Parkinson's disease (PD), using a combination of age, family history, hyposmia, and substantia nigra enlargement.

Although the battery was better than any single-screening instrument, "it is still too low for a feasible and cost-effective screening strategy," Daniela Berg (Hertie Institute for Clinical Brain Research, Tübingen, Germany) and colleagues note.

"Identification of subjects at increased risk to develop PD is a major requirement for the planning of clinical studies for neuroprotective interventions aiming to delay or prevent the onset of clinical disease," they comment in the European Journal of Neurology.

The study used data from the Prospective evaluation of Risk factors for Idiopathic Parkinson's Syndrome (PRIPS) cohort, which includes 1352 individuals aged 50 years or older who were free from PD at enrolment.

Age, gender, family history of PD, hyposmia, subtle motor impairment, and enlarged substantia nigra, as determined by hyperechogenicity (SN+), were recorded.

After 3 years of follow-up, 11 (0.7%) participants were diagnosed with incident PD.

Berg et al found that none of the single factors in isolation reached sufficient sensitivity and specificity to be a potential screening instrument.

They found that the best approach for prediction of incident PD comprised three steps: prescreening for age; primary screening for positive family history and/or hyposmia; and secondary screening for SN+.

When this approach was applied retrospectively to the cohort, 132 (9.9%) of the cohort were considered to be at increased risk for PD, of whom eight (6.1%) developed PD.

Individuals identified by screening therefore had a 9.3-fold increased risk for the development of PD within 3 years compared with low-risk participants.

The screening tool was 80.0% sensitive and 91.0% specific for identification of PD patients, with a positive predictive value of 6.1%.

However, this sensitivity value is lower than the target 90% or above set by the researchers.

Berg et al therefore say: "Further markers, i.e. a third stage screen to prove a dopaminergic deficit, will be needed to increase the PPV of such screening and treatment programs."

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