Comparison of lung function in children with CF and healthy controls
| n | CF | n | HC | Mean Difference (CF-HC) (95% CI) | p value | |
| Spirometry | 60 | 54 | ||||
| FEV0.75 z-score | −1.7 (1.5) | −0.5 (1.0) | −1.3 (−1.7 to −0.8) | <0.001 | ||
| FEV0.75 % pred | 78.6 (18.7) | 94.3 (12.4) | −15.7 (−21.7 to −9.7) | <0.001 | ||
| FEV1 z-score | −1.4 (1.4) | −0.2 (0.9) | −1.2 (−1.6 to −0.7) | <0.001 | ||
| FEV1 % pred | 81.6 (18.3) | 97.0 (12.3) | −15.4 (−21.3 to −9.6) | <0.001 | ||
| FVC z-score | −0.6 (1.3) | −0.1 (0.9) | −0.5 (−0.9 to −0.1) | 0.022 | ||
| FVC %pred | 92.0 (16.8) | 98.6 (11.9) | −6.6 (−12.0 to −0.1.1) | 0.019 | ||
| FEV1/FVC z-score | −1.4 (1.09) | −0.3 (1.0) | −1.2 (−1.5 to −0.8) | <0.001 | ||
| FEV1/FVC %pred | 87.8 (10.6) | 97.6 (6.6) | −9.8 (−13.1 to 90.5) | <0.001 | ||
| FEF25-75 z-score | −1.9 (1.5) | −0.5 (1.1) | −1.4 (−1.9 to −0.9) | <0.001 | ||
| FEF25-75 % pred | 61.3 (29.3) | 89.1 (24.7) | −27.8 (68.8 to 80.2) | <0.001 | ||
| MBW | 56 | 52 | ||||
| LCI | 10.2 (2.7) | 6.6 (0.5) | 3.6 (2.8 to 4.3) | <0.001 | ||
| FRCMBW z-score | −0.70 (1.2) | −0.81 (1.1) | 0.11 (−0.32 to 0.54) | 0.61 | ||
| Plethysmography | 60 | 54 | ||||
| sReff kPa.s | 1.6 (0.6) | 1.2 (0.2) | 0.4 (0.2 to 0.6) | <0.001 | ||
| sReff z-score | 1.6 (1.5) | 0.5 (0.9) | 1.1 (0.7 to 1.6) | <0.001 | ||
| sRtot kPa.s | 1.7 (0.6) | 1.3 (0.3) | 0.4 (0.2 to 0.6) | <0.001 | ||
| sRtot z-score | 1.5 (1.4) | 0.4 (0.9) | 1.1 (0.6 to 1.5) | <0.001 | ||
| FRCpleth z-score | 47 | 0.2 (1.3) | 44 | −0.9 (0.7) | 1.1 (0.6 to 1.5) | <0.001 |
| FRCpleth % pred | 47 | 104.4 (22.8) | 44 | 84.8 (11.8) | 19.6 (12.0 to 27.3) | <0.001 |
| RV z-score | 45 | 0.8 (1.4) | 40 | −0.4 (0.7) | 1.2 (0.7 to 1.7) | <0.001 |
| RV %pred | 45 | 122.3 (39.1) | 40 | 89.1 (19.4) | 33.3 (19.6 to 46.9) | <0.001 |
| TLC z-score | 45 | 0.4 (0.8) | 40 | −0.3 (0.6) | 0.7 (0.4 to 1.0) | <0.001 |
| TLC %pred | 45 | 107.9 (11.6) | 40 | 96.8 (9.1) | 11.1 (6.6 to 15.7) | <0.001 |
The reference equations for calculating z-scores and % predicted were from Stanojevic et al for Spirometry31;
Stocks and Quanjer for FRCMBW;33 Kirkby et al for Specific Resistance25 and Rosenthal et al for plethysmographic lung volumes.30