Table 2– Background, laboratory findings, and blood gas analysis and pulmonary function test results in each patient group with lung disease directly associated with rheumatoid arthritis (RA-LD)

	UIP	Bronchiectasis	NSIP	Bronchiolitis	OP	DAD	Combined	p-value
Males/females	33/24	4/27	6/10	2/9	4/1	4/1	7/12	<0.001
Age at rheumatoid arthritis onset yrs	60.2±12.8	46.2±14.3	52.3±12.5	50.8±11.6	63.8±8.2	59.4±12.9	58.1±16.8	<0.001
Age at RA-LD onset yrs	67.7±9.4	61.7±10.5	61.3±6.9	62.4±8.7	64.8±9.5	65.2±7.8	68.3±11.1	0.016
Duration of rheumatoid arthritis yrs	7.5±11.6	15.5±12.9	9.1±13.2	11.5±14.9	1.0±2.0	5.8±8.3	10.2±11.0	0.029
Smokers/nonsmokers	29/28	5/26	7/9	1/10	3/2	3/2	6/13	0.005
Smoking history pack-yrs	25.8±35.4	4.7±12.1	13.3±20.9	1.2±4.1	24.8±22.7	32.0±30.3	14.8±26.2	0.003
Steroid use/nonuse before RA-LD	41/16	10/21	8/8	7/4	2/3	3/2	11/8	0.021
DMARDs use/nonuse before RA-LD	38/19	20/11	12/4	9/2	4/1	2/3	12/7	0.749
WBCs cells·μL⁻¹	10130±5243	9142±4428	8638±3458	8564±3558	6500±1012	13080±3813	8531±2415	0.097
LDH U·L⁻¹	439±598	225±80	274±108	256±90	176±26	743±42	245±108	<0.001
CRP mg·dL⁻¹	8.4±8.4	5.6±7.5	5.2±8.4	2.3±3.3	7.2±1.7	17.2±15.0	4.5±6.7	0.008
ESR mm·h⁻¹	77.7±37.4	62.0±35.3	63.2±31.2	63.1±44.0	77.3±29.5	81.0±17.5	69.0±38.0	0.416
RF IU·mL⁻¹	509±1068	224±354	242±563	317±369	439±434	946±984	8221±2402	0.672
KL-6 U·L⁻¹	797±588	299±104	783±1095	770±700	367±191	1158±350	411±187	<0.001
P_a,O₂ mmHg	65.2±14.1	73.1±14.2	83.0±13.4	70.0±15.3	77.8±7.5	45.7±10.4	70.0±13.0	0.003
P_a,CO₂ mmHg	36.9±4.5	37.2±4.6	40.3±2.9	45.5±5.6	40.0±6.1	30.7±5.3	40.0±8.4	0.004
P_A–a,O₂ mmHg	39±17	30±13	17±14	23±13	29±24	66±16	30±17	0.001
VC % pred	70.4±18.0	79.9±18.9	76.2±14.2	75.9±20.6	71.0±21.8	65.4±3.3^#	75.0±18.0	0.519
FEV₁/FVC %	80.1±10.0	86.2±14.6	80.7±10.0	69.6±12.3	82.0±15.4	78.8±2.6^#	78.0±15.0	0.059
D_L,CO % pred	78.9±13.9	86.8±14.6	79.1±11.1	92.4±15.8	85.8±21.1	77.2±4.0^#	85.0±12.0	0.172

Data are presented as mean±sd or n. UIP: usual interstitial pneumonia; NSIP: nonspecific interstitial pneumonia; OP: organising pneumonia; DAD: diffuse alveolar damage; DMARD: disease-modifying anti-rheumatic drug; WBC: white blood cell; LDH: lactate dehydrogenase; CRP: C-reactive protein; ESR: erythrocyte sedimentation rate; RF: rheumatoid factor; KL: Krebs von den Lungen; P_a,O₂: arterial oxygen tension; P_a,CO₂: arterial carbon dioxide tension; P_A–a,O₂: alveolar–arterial oxygen tension difference; VC: vital capacity; % pred: % predicted; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; D_L,CO: diffusing capacity of the lung for carbon monoxide. ^#: pulmonary function test results were unavailable for three of the DAD patients (thus n = 2).