Development and evaluation of a standardized ELISA for the determination of autoantibodies against cN-1A (Mup44, NT5C1A) in sporadic inclusion body myositis

Table 1 Anti-cN-1A reactivity in sera from patients with sporadic inclusion body myositis, disease controls and healthy controls as determined by anti-cN-1A IgG ELISA at the RDL Reference Laboratory (Los Angeles, CA, USA)

Cohorts	Subgroups	n	Anti-cN-1A ELISA (IgG)
Cohorts	Subgroups	n	Positive	Negative	Sensitivity (CI 95%)	Specificity (CI 95%)
sIBM	Definite sIBM	17	8	9	47.1% (26.2–69.0%)
sIBM	Suspected sIBM^a	14	3	11	21.4% (6.8–48.3%)
Total sIBM		31	11	20	35.5% (21.1–53.1%)
Myositis controls	Polymyositis	7	0	7		100.0% (59.6–100.0%)
	Dermatomyositis	4	0	4		100.0% (45.4–100.0%)
	Unspecified myositis without sIBM^b	94	4	90		95.7% (89.2–98.7%)
	Muscle atrophy	1	0	1		100.0% (16.8–100.0%)
	Myonecrosis	4	0	4		100.0% (45.4–100.0%)
Other autoimmune disease controls	Systemic lupus erythematosus	33	2	31		93.9% (79.4–99.3%)
	Scleroderma	20	2	18		90.0% (68.7–98.4%)
	Sjögren’s syndrome	20	0	20		100.0% (81.0–100.0%)
	Rheumatoid arthritis	20	1	19		95.0% (74.6–100.0%)
Healthy controls		52	1	51		98.1% (88.9–100.0%)
Total controls		255	10	245		96.1% (92.8–98.0%)

CI confidence interval, cN-1A cytosolic 5′-nucleotidase 1A, sIBM sporadic inclusion body myositis
^aSuspected sIBM include biopsy readings of possible, probable and doubtful sIBM patients
^bUnspecified myositis without sIBM include idiopathic inflammatory myopathy (polymyositis, dermatomyositis and uncharacterized myositis) with no available biopsy data for this study

ISSN: 2038-3274