Table 2.
Mixed effects regression analysis according to analytical method, use of nose clip, smoking status, and age category.
| Parameters | β Coefficient | [95% Conf. Interval] | P > |t| |
|---|---|---|---|
| Analytical method | |||
| HPLCfluo/TBA (n = 9) | reference | ||
| Spectro/TBA (n = 2) | 0.30 | [−0.902; 1.49] | 0.59 |
| MS/DNPH (n = 9) | −1.03 | [−2.02; 0.032] | 0.04 |
| HPLCfluo/NA (n = 2) | 1.26 | [−0.079; 2.6] | 0.06 |
| Factor-specific Wald test | 0.04 | ||
| Use of nose clip | |||
| Yes (n = 9) | reference | ||
| No (n = 8) | 0.64 | [−0.52; 1.81] | 0.25 |
| NA/other (n = 5) | 1.14 | [0.32; 1.96] | 0.01 |
| Factor-specific Wald test | 0.04 | ||
| Smoking habit | |||
| Non-smokers (n = 11) | reference | ||
| Mixed population (n = 3) | −0.71 | [−1.70; 0.28] | 0.14 |
| Smokers (n = 5) | 0.8 | [0.08; 1.51] | 0.03 |
| NA (n = 3) | 0.37 | [−0.57; 1.31] | 0.4 |
| Factor-specific Wald test | 0.04 | ||
| Mean age (years) | |||
| <30 (n = 4) | reference | ||
| 30–<40 (n = 8) | 0.88 | [−0.014; 1.77] | 0.05 |
| 40–<50 (n = 3) | 0.82 | [−0.51; 2.16] | 0.2 |
| ≥50 (n = 7) | 1.21 | [0.09; 2.33] | 0.04 |
| Factor-specific Wald test | 0.15 | ||
| Intercept | −1.15 | [−2.07; −0.22] | 0.02 |
HPLCfluo/TBA—high-performance liquid chromatography fluorescence/thiobarbituric acid; spectro/TBA—spectrophotometry/thiobarbituric acid; MS—mass spectroscopy; NA—information not available.