Table 1.

Demographics and clinical characteristics of the study population and the study results of their lung biopsies.

Characteristics		Controls	All ILD*	CTD-related ILD	Idiopathic ILD	p-value (controls vs all ILD)
n patients		13	30	15	14
Female sex		62	47	67	29	0.37
Age, mean years (SD)		67.4 (13.7)	50.0 (11.2)	49.1 (10.7)	51.0 (12.6)	<0.001
Smoking behaviour	Never	10	44	50	36	0.16
	Previous	70	48	50	46
	Current	20	8	0	18
FVC, % of predicted		101 (90–105)	84 (67–88)	85 (69–89)	83 (64–85)	<0.001
n biopsies		13	47	26	19
MDA, μmol/g lung tissue		91 (87–101)	101 (91–131)	105 (90–133)	101 (96–117)	0.044
COX/SDH-ratio		0.12 (0.11–0.18)	0.10 (0.04–0.13)	0.10 (0.04–0.13)	0.10 (0.04–0.12)	<0.001
mtDNA, copies/pulmonary cell		315 (267–471)	419 (323–527)	367 (301–484)	434 (365–542)	0.088
COX2/COX4-ratio		2.18 (2.10–2.43)	0.64 (0.51–0.89)	0.62 (0.51–0.89)	0.72 (0.53–0.89)	<0.001
common deletion, % of mtDNA molecules		0 (0–13)	17 (0–32)	21 (0–36)	15 (0–29)	<0.001

Presented are either percent or median (interquartile range) if not otherwise specified.

COX2/COX4, cytochrome c-oxidase subunit 2 protein normalized for cytochrome c-oxidase subunit 4 protein; COX/SDH-ratio, cytochrome c-oxidase/ succinate dehydrogenase activity ratio; CTD, connective tissue disease; ILD, interstitial lung disease; MDA, malondialdehyde; mtDNA, mitochondrial DNA; FVC, forced vital capacity; SD, standard deviation.

*In one patient it is unknown if the patient suffered from a CTD-related ILD or an idiopathic IDL.