Cell Ratio Differences in Peripheral Blood between Early- and Late-Onset Parkinson's Disease: A Case-Control Study

To explore the differences of immune disorders in peripheral blood between patients with early-onset Parkinson's disease (EOPD) and late-onset Parkinson's disease (LOPD).

We retrospectively reviewed medical records of Parkinson's disease (PD) patients and healthy controls between June 2002 and July 2017. At last, we included 117 PD patients who were divided into EOPD and LOPD according to whether onset age of PD was after 50 and 99 controls divided into E-Control (match for EOPD) and L-Control (match for LOPD) according to whether their age was after 53 which was onset age plus median of disease duration. We compared the ratios of cells between multiple groups and performed the multinominal logistic regression analysis to explore the relationship between ratios and subtypes of PD. We also carried out the receiver operating characteristic (ROC) curve analysis to estimate the diagnostic value of the variable.

Lymphocyte-red blood cell ratio (LRR) was lower in LOPD compared with that in EOPD or L-Control. LRR was also negatively associated with LOPD (OR: 0.623; 95% CI: 0.397-0.980; P=0.040). The ROC curve analysis showed the optimal cutoff value of 4.53 (×10^-4) of LRR for discrimination of LOPD versus L-Control (sensitivity: 0.596, specificity: 0.764). The area under curve (AUC) was 0.721. As for LOPD versus EOPD, the optimal threshold of LRR was 4.10 (×10^-4) (sensitivity: 0.516, specificity: 0.745). AUC was 0.641.

Peripheral immune disorders might play an important part in the pathological progression of LOPD. Also, LRR has potential diagnostic value.