Reference equations using generalised additive models of location, scale and shape models
| M=mu, median | (S)=sigma, coefficient of variation, which explains the variability around median | L, lamda, which is the index of skewness | |
| Females (n=530) | |||
| DLCO (mL/min/mm Hg) | exp(– 4.481+1.406‧ln(height)+0.194‧ ln(age)+0.0002‧altitude+Mspline) | exp(0.642‧ln(age) – 1.018·ln(height)+Sspline) | 0.325 |
| DLNO (mL/min/mm Hg) | exp(– 3.777+0.144‧machine+1.510‧ ln(height)+0.3405‧ln(age)+Mspline) | 0.1053 for Jaeger Masterscreen, 0.1401 for Hyp’Air | 0.836 |
| VA (L) | exp(– 8.323+0.060‧machine+1.842‧ ln(height)+0.1705‧ln(age)+Mspline) | exp(–0.616‧ln(height)+0.2485‧ln(age)) | 0.577 |
| Males (n=546) | |||
| DLCO (mL/min/mm Hg) | exp(– 5.163+1.500‧ln(height)+0.3507‧ ln(age)+0.0002‧altitude+Mspline) | exp(8.365+0.914‧ln(age) –2.503·ln(height)+Sspline) | 0.632 |
| DLNO (mL/min/mm Hg) | exp(– 4.339+0.138‧machine+1.617‧ ln(height)+0.410‧ln(age)+Mspline) | Exp(0.230‧machine – 2.191) | 1.113 |
| VA (L) | exp(– 9.443+0.0569‧machine+2.076‧ ln(height)+0.169‧ln(age)+Mspline) | 0.1016 | 0.0635 |
Height is in cm, age in years; Machine=1 for Hyp’Air Compact and 0 for the Jaeger Masterscreen; lower limits of normal (fifth percentile)=exp(ln(M)+ln(1–1.645‧L‧S)/L); Per cent predicted = (measured/M)‧100; Z-score = ((measured value/M)L – 1)/(L·S); exp ()=natural exponential; ln()=natural logarithm; Mspline and Sspline correspond to the age-varying coefficients provided in the supplementary materials. Model is valid from ages 5–95 years of age and an altitude of 0–300 m. Note: If pulmonary diffusing capacity for carbon monoxide (DLCO) is measured at an altitude that is more than 300 m, we recommend converting the measured DLCO to sea level first, based on the data by Gray et al,80 and then omitting the altitude covariate from the equation (as the converted DLCO will be at an altitude of 0 m). Adjusted DLCO to sea level (mL/min/mm Hg)=measured DLCO at altitude·(0.505+0.00065·barometric pressure in mm Hg at altitude). The formula to estimate barometric pressure at altitude in mm Hg is: 760·exp(– 0.284·altitude in m / (8.314·Temperature in Kelvin)), where Kelvin = °C+273.15. (see: https://planetcalc.com/938/).
DLCO, pulmonary diffusing capacity for carbon monoxide; DLNO, pulmonary diffusing capacity for nitric oxide; VA, alveolar volume.