FEV1/FVC Ratio: GLI-2012 Equation-Derived Percentiles
These percentiles come directly from the Global Lung Function Initiative 2012 (GLI-2012) LMS equation for FEV1/FVC, published by Quanjer et al. (DOI: 10.1183/09031936.00080312). GLI fitted a dedicated equation to observed ratios rather than dividing separately predicted FEV1 and FVC values. FitnessNorms calculates one representative point at each age-bracket midpoint and one NHANES median height; the rows are not empirical distributions pooled across the full brackets.
- Equations: the coefficient set GLI-2012 labels "Caucasian" is used, with all group-adjustment flags set to zero. The model was fitted with 74,187 records across four groups; 57,395 records were in this source-labelled group.
- L equation: for males,
L = q0 + q1 x ln(age) + Lspline. For females,L = q0 + q1 x ln(age); the female workbook Lspline column is zero. - M and S equations:
M = exp(a0 + a1 x ln(height) + a2 x ln(age) + Mspline)andS = exp(p0 + p1 x ln(age) + Sspline)use ratio-specific coefficients and interpolated spline values. - Age and height assumptions: each row is evaluated at the continuous midpoint shown by the chart (for example, age 25 for 20-29 and age 85 for 80+) and at one NHANES median standing height for that sex and bracket (the survey-weighted median of measured standing height in NHANES 2015-2018, computed from the public examination files; see NHANES 2015-2018 median heights). Height has a smaller but non-zero effect on the fitted ratio.
- Percentile formula:
P = M x (1 + L x S x z)1/L, where z is the standard normal quantile. P5, P25, P50, P75, and P95 are calculated directly and rounded to 0.001.
| Coefficient | Males | Females |
|---|---|---|
| a0 (intercept) | 0.7403 | 0.550559 |
| a1 (ln height) | -0.1595 | -0.107805 |
| a2 (ln age) | -0.0366 | -0.054419 |
| p0 (S intercept) | -2.9595 | -3.23948 |
| p1 (S x ln age) | 0.1156 | 0.18503 |
| q0 (L intercept) | 4.7101 | 7.032 |
| q1 (L x ln age) | -0.6774 | -1.197 |
| L includes Lspline? | yes | no |
| Bracket | Evaluation age | Males (cm) | Females (cm) |
|---|---|---|---|
| 5-9 | 7.5 | 126.2 | 123.8 |
| 10-14 | 12.5 | 155.6 | 154.6 |
| 15-19 | 17.5 | 174.1 | 161.8 |
| 20-29 | 25 | 176.0 | 162.9 |
| 30-39 | 35 | 176.7 | 162.6 |
| 40-49 | 45 | 176.5 | 162.6 |
| 50-59 | 55 | 175.4 | 161.0 |
| 60-69 | 65 | 174.3 | 160.9 |
| 70-79 | 75 | 173.1 | 158.0 |
| 80+ | 85 | 170.4 | 155.9 |
This is an archival reproduction of one GLI-2012 group-specific equation, not a current clinical calculator. In 2023 the ATS, with ERS endorsement, recommended race-neutral interpretation and identified GLI Global as the available average equation (Bhakta et al. 2023). GLI-2012 covers ages 3-95, and its supplement explicitly advises caution above age 80 because data are sparse. The independent checker recalculates all published cells directly from the verified workbook.
The ratio is not a higher-is-better or lower-is-better metric. Age/sex pages therefore omit performance ratings, reference lines, and tinted performance bands. Full source details are on the GLI-2012 reference page.