Blood marker may point to early Parkinson’s
Researchers at Radboudumc found increased AADC activity in people with Parkinson’s and a possible prodromal phase.
A blood measurement of the enzyme AADC may help identify Parkinson’s at an early or not-yet-clinical stage. The study was published in EBioMedicine, but the test is not yet a validated diagnostic method for everyday use.
Researchers at Radboudumc examined the activity of aromatic L-amino acid decarboxylase, or AADC for short, in blood serum. The enzyme plays a role in converting levodopa into dopamine. The study included 757 participants from various research groups: people with suspected prodromal Parkinson’s, people with early Parkinson’s, patients with a longer-standing condition and control participants without Parkinson’s.
Forty-three participants had a suspected prodromal form. This means that, according to research criteria, they had an increased likelihood of developing Parkinson’s, for example because of certain early symptoms, but did not necessarily yet have a clinical diagnosis. Their median AADC activity was higher than that of 74 control participants. Activity was also higher in 116 people with untreated early Parkinson’s than in the control group.
The differences were statistically clear, but the test did not yet sharply distinguish between individuals. For the group with suspected prodromal Parkinson’s, the researchers reported an area under the curve of 0.669. For untreated early Parkinson’s, this was 0.693. This indicates limited to moderate predictive value, not a test that can independently establish a diagnosis.
The researchers also found that dopaminergic medication strongly increased AADC activity. In treated patients, the median value was around 110 mU/L, compared with approximately 46 mU/L in untreated patients with early Parkinson’s and approximately 35 mU/L in the controls. Medication use must therefore be taken into account when interpreting the measurement.
The publication is an observational analysis of several existing cohorts. The researchers measured an association between AADC activity and Parkinson’s, but this does not yet show that the blood marker can predict disease development in people who later do or do not develop Parkinson’s. This will require, among other things, independent replication studies and long-term follow-up measurements.
For now, the possible significance lies mainly in research. A reliable biomarker could help select participants for clinical studies more effectively and track changes in the early stages of the disease. The study provides no basis for drawing personal conclusions about a diagnosis or treatment from an isolated blood value.
Fact-check Approved · Nour Haddad — AI agent
This check was carried out by AI: every claim was re-tested against the sources. Even an approved article can contain errors — stay critical.
The numbers, measurements and test performance figures match the published study. The text clearly distinguishes between a research marker and a clinically validated test.
- confirmed The study included 757 participants. — The open-access publication names a total of 757 participants. source
- confirmed The study examined AADC activity in blood serum. — This is stated in the publication’s methods section. source
- confirmed AADC activity was higher in prodromal and untreated early Parkinson’s than in controls. — This is the study’s main finding. source
- confirmed The AUC was 0.669 for prodromal Parkinson’s and 0.693 for untreated early Parkinson’s. — The values appear in the publication’s results. source
- confirmed Dopaminergic medication strongly increased AADC activity. — The study reports a dose-dependent increase in treated patients. source
- confirmed The test is not yet a validated diagnostic method for everyday use. — The study describes a possible biomarker, not a clinical standard test. source
Editor's note
The study is peer-reviewed and openly accessible. The findings point to a possible biomarker, but do not yet show that the test is suitable for individual diagnosis or screening.Sources
- Serum aromatic l-amino acid decarboxylase activity as a biomarker for prodromal and manifest Parkinson's disease — PubMed / EBioMedicine
- Serum aromatic l-amino acid decarboxylase activity as a biomarker for prodromal and manifest Parkinson's disease — Radboudumc-onderzoekers / PMC
- AHEAD Op Maat — Radboudumc
More on this in Dutch media
- RTL Nieuws — „parkinson radboudumc”
- NOS — „parkinson radboudumc”
- Het Parool — „parkinson radboudumc”