FVC: GLI-2012 Equation-Derived Percentiles
The Global Lung Function Initiative 2012 (GLI-2012) equations (Quanjer et al., DOI: 10.1183/09031936.00080312) model FVC continuously by exact age and height. FitnessNorms converts that continuous model into display brackets by calculating one representative point per bracket. These are equation-derived reference percentiles at the stated age and height, not empirical percentiles pooled across every person in the age band.
- 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. Mspline and Sspline are read from the official lookup workbook and linearly interpolated at the bracket midpoint. FVC uses constant
L = q0for both sexes; its workbook Lspline column is zero. - 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). It is not an average over the bracket. Heights used (cm) are below.
- 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 0.01 L.
| 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 derivation scripts verify the official workbook's SHA-256 and an independent checker recalculates all published cells directly from its coefficient and spline sheets. Full source details and limitations are on the GLI-2012 reference page.