3.2.2 short- and mid-term repeatability
Short-term repeatability of LCI and FRC was assessed in sixteen children
with CF and is summarized in Supplemental Table 1. Average LCI in
children with CF was lower when analyzed in Spiroware 3.3.1 (LCI 9.4 (SD
1.8) vs. 10.8 (2.2)). In general, repeatability of MBW measurements was
similar when analyzed in Spiroware 3.2.1 and 3.3.1. Variability between
measurements expressed as CV% increased slightly in Spiroware 3.3.1
(LCI: 4.2 vs 3.7; FRC 3.7 vs 3.6). Also when expressing relative
differences between measurements, the upper limit of normal (95%
quantile) increased marginally (9.1 vs 8.4%).
Mid-term repeatability of LCI measurements was assessed in 12 healthy
children and 23 children with CF, results are summarized in Supplemental
Table 1. Mean (SD) LCI in healthy children was 6.8 (0.4) when assessed
in Spiroware 3.2.1 and 6.1 (0.3) in Spiroware 3.3.1, in children with CF
mean (SD) LCI was 11.6 (2.6) and 9.7 (2.2) in Spiroware 3.2.1 and 3.3.1,
respectively. Repeatability indices were similar when assessed in
Spiroware 3.2.1 and 3.3.1. While variability tended to be lower in
healthy children when analyzed in Spiroware 3.3.1 (CV% 3.4 vs 4.4) this
was the opposite in children with CF (CV% 9.6 (3.3.1) vs 8.1 (3.2.1).
Similarly, when assessing relative changes between visits, the upper
limit of normal (95% quantile) was lower in healthy children in
Spiroware 3.3.1 compared to 3.2.1 but higher in children with CF in
3.3.1 (Supplemental Table 1). While we found within-subject between test
standard deviation to be independent of the magnitude of LCI for both
Spiroware settings (Supplemental Figure 1), within-subject within-test
standard deviation was associated with the magnitude of LCI for both
settings (Spiroware 3.2.1: R2= 0.3
(p<0.001); 3.3.1: R2= 0.2
(p<0.001).
3.2.3 validity