Table 3

Relative risks (odds ratios with 95% confidence intervals, CI) of RF positive RA, RF negative RA, and total RA among tertiles^3-150 of serum IgG, IgA, and IgM concentrations

Tertiles		RF positive RA			RF negative RA				Total RA
Tertiles		Number of cases	Number of controls		Odds ratio	95% CI			Number of cases	Number of controls	Odds ratio	95% CI	Number of cases	Number of controls	Odds ratio	95% CI
IgG
Lowest	22	941	1.00		9	28	1.00			31	119	1.00
Middle	31	87	1.45	0.77–2.71	10	33	0.96	0.35–2.68		41	120	1.30	0.76–2.22
Highest	35	79	1.88	1.01–3.52	15	39	0.21	0.43–3.37		50	118	1.68	0.99–2.86
p for trend			0.01				0.69					0.05
IgA
Lowest	18	82	1.00		15	38	1.00			33	120	1.00
Middle	36	84	1.93	1.02–3.66	12	35	0.84	0.34–2.06		48	119	1.48	0.89–2.47
Highest	34	91	1.67	0.86–3.24	7	27	0.62	0.20–1.94		41	118	1.28	0.74–2.22
p for trend			0.14				0.41					0.37
IgM
Lowest	29	87	1.00		14	32	1.00			43	119	1.00
Middle	31	85	1.06	0.59–1.90	9	35	0.53	0.18–1.55		40	120	0.90	0.54–1.49
Highest	28	85	0.98	0.52–1.83	11	33	0.69	0.26–1.84		39	118	0.89	0.53–1.51
p for trend			0.95				0.48					0.67

↵3-150 The tertiles are based on the distribution of concentrations (g/l) among controls. Tertile divisions are, for IgG < 12.21, 12.22-15.00, > 15.00 among men and < 12.97, 12.97-15.33, > 15.33 among women; for IgA < 2.12, 2.12-3.10, > 3.10 among men and < 1.87, 1.87-2.76, > 2.76 among women; and for IgM < 1.06, 1.06-1.52, > 1.52 among men and < 1.57, 1.57-2.41, > 2.41 among women.