TABLE 2.

Anti-ENA antibodies most commonly detected by different methods and their performance characteristics^a

ENA	Major clinical associations	CIEP		ELISA		IB		Comments
		Se	Sp	Se	Sp	Se	Sp
SS-A	Sjogren’s syndrome	85-95	50-60	90-97	45-50	70-85	40-50	Conformational epitopes on 52- and 60-kDa SS-A antigen best detected by CIEP; IB is unreliable because of denaturation of epitopes by SDS-PAGE
SLE	25-30	50-60	35-60	45-50	10-15	40-50
SS-B	Sjogren’s syndrome	70-80	60-70	75-85	50-60	90-95	55-65	Linear epitopes on 48-kDa SS-B antigen best detected by IB; CIEP is less sensitive but more specific
SLE	10-15	50-55	20-30	45-50	30-35	40-50
Sm	SLE	30-35	98-100	35-50	55-99	30-35	95-99	ELISA specificity may be improved by use of highly purified or recombinant antigens; IB is more specific than ELISA
U1 RNP	Mixed CTD	90-95	60-75	95-98	50-60	80-85	65-75	ELISA specificity may be improved by use of highly purified or recombinant antigens; IB is more specific than ELISA
SLE	15-35	55-75	50-60	50-55	30-40	55-70
Scl-70	Scleroderma	25-35	95-99	30-45	80-90	30-45	90-95	CIEP is less sensitive because of the low negative charge on Scl-70 antigen at pH 8.0; this factor can be improved by running gel electrophoresis at pH 8.4
	SLE	0-5	0-5	20-25	15-25	10-20	5-10	Anti-Scl-70 antibodies detected by ELISA in SLE may not be “false positives”; rather, they may identify a subgroup of patients at high risk of pulmonary hypertension and renal disease
Jo-1	PM/DMb	25-40	95-99	35-45	90-95	60-90	95-99	Anti-Jo-1 antibodies stain the cytoplasm of HEp-2 cells and may be reported as“ANA negative”

^aSensitivities (Se) and specificities (Sp) for the associated clinical conditions are given as percentages and are estimates based on interpretation of the available literature.

^bPM/DM, polymyositis and dermatomyositis.