Table 2. Diffusing capacity of carbon monoxide (DLCO) values for participants by Indigenous status, stratified by sex and age (≤ 35 & > 35 years).

	Indigenous Australian (n = 129)	Australian Caucasians (n = 197)	p-value
Total sample
DLCO (ml/min/mm/Hg)	18.75 (17.65, 19.85)	23.05 (22.13, 23.97)	<0.01*
DLCO (%)	71 (68, 74)	86 (84, 89)	<0.01*
DLCO LLN	20.16 (19.45, 20.86)	20.4 (19.82, 20.99)	0.99
DLCO < LLN	82 (64%)	49 (25%)	<0.01*
Females
≤ 35 years	n = 14 (18%)	n = 11 (9%)
DLCO (ml/min/mm/Hg)	20.23 (17.59, 22.87)	25.87 (21.79, 29.95)	<0.01*
DLCO (%)	78.29 (70.27, 86.3)	89.73 (76.93, 102.53)	0.10
DLCO LLN	20.19 (18.76, 21.63)	23.03 (22.07, 23.99)	<0.01*
DLCO < LLN	7 (50%)	4 (36%)	0.50
> 35 years	n = 66 (82%)	n = 124 (91%)
DLCO (ml/min/mm/Hg)	16.47 (15.32, 17.61)	20.03 (19.3, 20.76)	<0.01*
DLCO (%)	70.21 (66.05, 74.38)	84.16 (81.42, 86.9)	<0.01*
DLCO LLN	17.7 (17.05, 18.35)	18.1 (17.68, 18.53)	0.29
DLCO < LLN	42 (64%)	32 (26%)	<0.01*
Males
≤ 35 years	n = 14 (29%)	n = 11 (18%)
DLCO (ml/min/mm/Hg)	26.59 (22.13, 31.05)	33.72 (29.59, 37.84)	0.02*
DLCO (%)	77.21 (64.83, 89.6)	98.55 (89.79, 107.3)	0.01*
DLCO LLN	27.5 (26.3, 28.7)	27.14 (24.61, 29.66)	0.76
DLCO < LLN	9 (64%)	1 (9%)	0.01*
> 35 years	n = 35 (71%)	n = 51 (82%)
DLCO (ml/min/mm/Hg)	19.33 (17.1, 21.57)	27.48 (25.64, 29.32)	<0.01*
DLCO (%)	67 (60.08, 73.92)	88.33 (83.68, 92.99)	<0.01*
DLCO LLN	21.83 (20.92, 22.74)	23.98 (22.97, 24.98)	<0.01*
DLCO < LLN	24 (69%)	12 (24%)	<0.01*

Abbreviations: DLCO, diffusing capacity of carbon monoxide; LLN, lower limit of normal.

Data were expressed as mean (95% confidence interval) and number (%).

DLCO (%, LLN) data were derived from the NHANES (National Health and Nutrition Examination Survey) norms.

Differences between groups tested with two-tailed students T-test for continuous parameters and proportions z-test for categorical parameters.

*Denote statistically significant differences (p<0.05).