Table 2. Significant differences in concentrations of amino acids among three groups of PD patients compared using Kruskal-Wallis test.

Amino acid	ePD n = 22 mean±SD (μmol/l); median	aPD LID+ n = 28 mean±SD (μmol/l); median	aPD LID- n = 23 mean±SD (μmol/l); median	p- value
Alanine	430.8±70.2; 430.6	382.2±107.0; 367.1	393.5±100.4; 383.6	0.048
Arginine	109.4±25.4; 101.8	90.8±15.6; 92.0	92.9±19.8; 93.9	0.008
Phenylalanine	67.9±9.4; 69.7	59.4±8.1; 59.3	63.2±9.6; 62.1	0.008
Threonine	125.7±33.6; 116.6	145.0±35.1; 136.0	148.7±35.2; 148.2	0.021

ePD- early Parkinson’s disease stadium; aPD LID+ advanced Parkinson’s disease stadium with dyskinesia, aPD LID- advanced Parkinson’s disease stadium without dyskinesia.