Table 3. . Percent stability (mean ± SD) of kynurenine analytes at room temperature after 30 min, 1, 2, 3, 4 and 24 h.
| Compound | Baseline mean ± SD | % change | |||||
|---|---|---|---|---|---|---|---|
| 30 min | 1 h | 2 h | 3 | 4 h | 24 h | ||
| TRP | 1.5 ± 0.5 μM | 105 ± 4.9 | 105 ± 4.9 | 99 ± 4.9 | 101 ± 4.9 | 105 ± 4.9 | 95 ± 2.4 |
| L-KYN | 60.2 ± 30.6 nM | 95 ± 4.1 | 96 ± 4.1 | 93 ± 4.1 | 96 ± 4.0 | 100 ± 2.7 | 95 ± 8.8 |
| KYNA | 2.4 ± 0.8 nM | 113 ± 4.9 | 102 ± 4.9 | 89 ± 4.9 | 100 ± 4.7 | 109 ± 4.7 | 99 ± 1.6 |
| QUIN | 23.6 ± 19.7 nM | 103 ± 5.9 | 106.2 ± 1.6 | 100 ± 4.6 | 101 ± 4.4 | 108 ± 2.5 | 111 ± 7.3 |
| PIC | 14.5 ± 3.0 nM | 98 ± 4.8 | 101 ± 4.2 | 96 ± 4.5 | 99 ± 4.0 | 104 ± 4.6 | 98 ± 4.9 |
| PIC/QUIN ratio | 0.8 | 104.4 ± 9.9 | 95.4 ± 5.1 | 96.4 ± 4.3 | 98.1 ± 5.6 | 96.6 ± 5.1 | 92,7 ± 4.3 |
| NAA | 22.8 ± 20.9 nM | 100 ± 6.1 | 102 ± 1.9 | 96 ± 6.4 | 103 ± 7.2 | 111 ± 7.2 | 104 ± 5.9 |
| 3-HK | 3.1 ± 1.2 nM | 99 ± 5.1 | 102 ± 2.9 | 97 ± 6.0 | 97 ± 4.1 | 102 ± 2.7 | 75 ± 4.0 |
Compared with 100% at t = 0, mean ± SD from 4 to 6 individual CSF samples. For baseline and all freeze–thaw cycles, n = 6.
3-HK: 3-Hydroxykynurenine; CSF: Cerebrospinal fluid; KYNA: Kynurenic acid; L-KYN: L-Kynurenine; NAA: Nicotine amide; PIC: Picolinic acid; QUIN: Quinolinic acid; SD: Standard deviation; TRP: Tryptophan.