Table 3. Mean spirometric values of the studied population (average of all longitudinal observations) expressed as Standard deviations (SD) from three cross-sectional reference values.
| Reference equation | Boys (n = 6,655) |
Girls (n = 7,509) |
||
|---|---|---|---|---|
| Mean (SD) | P value | Mean (SD) | P value | |
| Quanjer et al. (13) | ||||
| FEV1 | 0.76 (1.15) | p <0.001 | 0.59 (1.12) | <0.001 |
| FVC | 0.58 (1.11) | p <0.001 | 0.44 (1.09) | <0.001 |
| FEV1/FVC | 0.29 (1.04) | p <0.001 | 0.26 (1.05) | <0.001 |
| NHANES III (12) | ||||
| FEV1 | 0.28 (1.02) | p <0.001 | 0.19 (1.03) | <0.001 |
| FVC | 0.25 (0.97) | p <0.001 | 0.18 (0.97) | <0.001 |
| FEV1/FVC | 0.09 (1.14) | 0.003 | 0.05 (1.07) | 0.048 |
| PEF | 0.77 (0.87) | p <0.001 | 0.68 (1.01) | <0.001 |
| PEFadj | 0.17 (0.77) | p <0.001 | 0.03 (0.89) | 0.21 |
| Pérez-Padilla et al. (4) | ||||
| FEV1 | -0.04(1.00) | 0.11 | 0.06 (0.96) | 0.008 |
| FVC | -0.13 (1.00) | p <0.001 | -0.02 (0.97) | 0.42 |
| FEV1/FVC | 0.07 (0.99) | 0.005 | 0.26 (0.96) | <0.001 |
| PEF | 0.23 (0.90) | p <0.001 | 0.33 (0.94) | <0.001 |
P value testing the hypothesis that the measurement does not differ from zero, taking into account repeated measurements and the study sampling. Boys contributed with 6,655 observations and girls with 7,509. Ideal fit of equations would be a mean Z-score of 0 with an SD of 1. NHANES III = National Health and Nutrition Examination Survey; FEV1 = Forced expiratory volume at 1 sec; FVC = Forced vital capacity; FEV1/FVC = ratio of FEV1 and FVC; PEF = Peak expiratory flow; PEFadj = PEF in Mexico City adjusted for that expected at sea level, see Online Supporting Information.