Serum 5-hydroxytryptamine levels as biomarkers for motor dysfunction and depression in Parkinson’s disease patients

Figure 1 Combined effects of dyskinesia and depression on serum 5-hydroxytryptamine levels: Four-group analysis. This figure demonstrates a stepwise decline in serum 5-hydroxytryptamine levels across four patient subgroups stratified by the presence of dyskinesia and depression. Patients without either complication had the highest 5-hydroxytryptamine levels (215.7 ng/mL), followed by those with dyskinesia alone (178.9 ng/mL), depression alone (156.8 ng/mL), and both complications showing the lowest levels (122.4 ng/mL). ^aP < 0.001. 5-HT: 5-hydroxytryptamine.

Figure 2 Receiver operating characteristic curves for predicting Parkinson’s disease complications using serum 5-hydroxytryptamine levels. Receiver operating characteristic curves compare the diagnostic performance of serum 5-hydroxytryptamine levels for different Parkinson’s disease complications. The red curve represents dyskinesia prediction [area under the curve (AUC) = 0.782], the purple curve represents depression prediction (AUC = 0.798), and the green curve represents composite outcome prediction (AUC = 0.834). The gray dashed line indicates the random prediction reference line (AUC = 0.5). The composite outcome model shows the best diagnostic performance, suggesting that serum 5-hydroxytryptamine can serve as a comprehensive biomarker for both motor and non-motor complications in Parkinson’s disease. All AUC values are statistically significant (P < 0.001). AUC: Area under the curve.