Rotated factor loadings for traditional# measures
| Variable | Traditional factor 1 | Traditional factor 2 |
| FEV1 | 0.155 | 0.932¶ |
| FVC | 0.051 | 0.924¶ |
| Mean morning PEF | −0.032 | 0.842¶ |
| Daytime salbutamol use (reversed+) | 0.768¶ | 0.001 |
| Per cent nights no waking | 0.701¶ | −0.047 |
| Night-time symptom score (reversed) | 0.820¶ | −0.046 |
| Daytime symptom score (reversed) | 0.792¶ | −0.093 |
| Night-time salbutamol use (reversed) | 0.795¶ | 0.129 |
| Per cent salbutamol-free 24 h | 0.767¶ | −0.160 |
Table shows the rotated factor loading between each individual variable and the factors derived from principal component analysis. FEV1: forced expiratory volume in one second; FVC: forced vital capacity; PEF: peak expiratory flow. #: FEV1/FVC, log provocative dose of methacholine causing a 20% fall in FEV1, FEV1 % predicted, PEF % best, PEF % predicted and symptom-free days contributed little and were omitted from the final factor analysis for traditional variables; ¶: Significant loadings, indicating the variables that clustered together, i.e. were strongly correlated with each other; +: values were reversed for parameters for which a higher raw score indicated worse asthma control.