Serum levels of B-cell activating factor of the TNF family (BAFF) correlate with anti-Jo-1 autoantibodies levels and disease activity in patients with anti-Jo-1positive polymyositis and dermatomyositis

Table 1 Demographic characteristics, clinical, and laboratory data of patients at time of blood sampling at initial evaluation

	DM (n = 22)		PM (n = 41)		All (n = 63)
Female:male	15:7		28:13		43:20
Age (years), mean ± SD	52.5 ± 10.9		52 ± 12.6		52.2 ± 11.9
Years of symptoms	5.9 (0.1–31.0)		3.8 (0.2–23.8)		4.1 (0.1–31.0)
Years from diagnosis	1.3 (0–29.0)		0.8 (0–23.3)		1.0 (0–29.0)
Early cases^a, n (%)	10 (45%)		20 (49%)		30 (48%)
ILD, n (%)	15 (68%)		33 (80.5%)		48 (76%)
Medication, n (%)
GC	20 (91%)		36 (88%)		56 (89%)
DMARDs	11 (50%)		23 (56%)		34 (54%)
No therapy	1 (4.5%)		4 (10%)		5 (8%)
Dose of GC (mg/day)^b	15 (0–80)		17.5 (0–85)		17.5 (0–85)
MDAAT visual analogue scale (mm)	(n = 20)		(n = 38)		(n = 58)
Constitutional	1 (0–35)		0 (0–25)		0 (0–35)
Cutaneous	10 (0–30)		0 (0–21)		1 (0–30)
Skeletal	0 (0–43)		0 (0–63)		0 (0–63)
Gastrointestinal	0 (0–17)		0 (0–27)		0 (0–27)
Pulmonary	11 (0–86)		13 (0–66)		12.5 (0–86)
Cardiac	0 (0–10)		0 (0–36)		0 (0–36)
Other	0 (0–17)		0 (0–29)		0 (0–29)
Extramuscular global	11.5 (0–64)		17.5 (0–44)		15 (0–64)
Muscle	7.5 (0–82)		11.3 (0–71)		11 (0–82)
Global	21 (0–79)		16.5 (0–59)		17.5 (0–79)
MYOACT score^c	0.07 (0–0.26)		0.05 (0–0.23)		0.06 (0–0.26)
	n		n		n
BAFF (ng/ml)	22	2.1 (0.8–20.9)	41	1.7 (0.3–18.7)	63	1.8 (0.3–20.9)
anti-Jo-1 (kU/l)	22	127 (0.6–2135)	41	178 (0.8–3605)	63	162 (0.6–3605)
CK (μkat/l)	22	1.8 (0.25–94.5)	41	3.6 (0.3–78.4)	63	2.6 (0.25–94.5)
Myoglobin (μg/l)	19	80 (24 - 5313)	34	115 (10.6–3498)	53	94 (10.6–5313)
ALT (μkat/l)	22	0.4 (0.1–6.7)	40	0.5 (0.1–3.6)	62	0.5 (0.1–6.7)
AST (μkat/l)	21	0.5 (0.1–5.1)	40	0.4 (0.2–6.5)	61	0.4 (0.1–6.5)
CRP (mg/l)	22	3.0 (0.2–29.4)	38	3.5 (0.5–54.8)	60	3.25 (0.2–54.8)

Data are shown as median (range; minimum–maximum) unless otherwise stated
Myoglobin normal levels < 92 μg/l for men and < 76 μg/l for women
ALT alanine aminotransferase (normal levels < 0.75 μkat/l for men and < 0.57 μkat/l for women), AST aspartate aminotransferase (normal levels < 0.58 μkat/L for men and < 0.52 μkat/L for women), BAFF B-cell activating factor of the tumour necrosis factor family, CK creatine kinase (normal levels for Swedish cohort < 2.5 μkat/L for men and < 2.0 μkat/L for women, and for Czech cohort < 2.85 μkat/l and < 2.42 μkat/l), CRP= C-reactive protein (normal levels < 5 mg/l), DM dermatomyositis, DMARD disease-modifying anti-rheumatic drug, GC glucocorticoids, ILD interstitial lung disease (ever present), MDAAT Myositis Disease Activity Assessment Tool, PM polymyositis
^aEarly case = disease duration up to 6 months
^bEquivalent of prednisone
^cMYOACT score is the sum of the 10-cm visual analogue scale scores for each of the six individual organ systems divided by the total maximum possible score

ISSN: 1478-6362