Table 3.
Intraclass correlation coefficients and between-occasion variability.
| Between-occasion variability - 1 year between tests |
||||
|---|---|---|---|---|
| Estimated ICC (95% CI) | Estimated mean difference (SD of the difference) | Limits of agreement | (95% CI LL)/(95% CI UL) | |
| FEV1 z-score | 0.87 (0.78; 0.92) | 0.02 (0.64) | −1.23 to 1.27 | (−1.52; −0.94)/(0.99; 1.53) |
| FEV1/FVC z-score | 0.88 (0.80; 0.93) | 0.03 (0.46) | −0.87 to 0.93 | (−1.09; −0.67)/(0.73; 1.12) |
| LCI | 0.83 (0.71; 0.89) | 0.51 (1.26) | −1.96 to 2.98 | (−2.49; −1.40)/(2.44; 3.56) |
| M1/M0 | 0.76 (0.62; 0.85) | 0.06 (0.33) | −0.59 to 0.71 | (−0.72; −0.43)/(0.55; 0.85) |
| M2/M0 | 0.77 (0.63; 0.85) | 0.90 (3.62) | −6.20 to 8.00 | (−7.78; −4.61)/(6.40; 9.72) |
| Cn@TO6 | 0.85 (0.74; 0.90) | 0.16 (0.95) | −1.70 to 2.02 | (−2.10; −1.28)/(1.61; 2.46) |
| Scond*VT | 0.53 (0.32; 0.68) | 0.00 (0.02) | −0.04 to 0.04 | (−0.05; −0.03)/(0.03; 0.05) |
| Sacin*VT | 0.86 (0.76; 0.91) | 0.01 (0.06) | −0.11 to 0.13 | (−0.12; −0.07)/(0.10; 0.15) |
Estimates of between-occasion variability were calculated as the limits of agreement between two test occasions with a 1-year interval and are presented with the estimated mean difference in the outcome and SD of the difference, and the calculated limits of agreement with 95% CI on the lower and upper limit of agreement, respectively.
ICC: intraclass correlation coefficient; LL: lower limit; UL: upper limit; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; LCI: lung clearance index; M1/M0: moment ratio to the first degree; M2/M0: moment ratio to the second degree; Cn@TO6: normalized N2 concentration at six lung volume turnovers; Scond*VT: regional ventilation inhomogeneity of the conducting airways corrected for tidal volume; Sacin*VT: regional ventilation inhomogeneity of the intra-acinar airways corrected for tidal volume.