Immunoglobulin G/immunoglobulin M autoantibody ratios in incomplete systemic lupus erythematosus

Figures & data

Table 1. Baseline characteristics.

	HCs (n = 11)	iSLE (n = 34)	SLE (n = 41)	p
Demographics
Age at inclusion (years)	28 (27–48)	39 (29–50)	43 (30–51)	0.32*
Female	10 (91)	30 (88)	33 (80)	0.64†
Ethnicity
Caucasian	11 (100)	30 (88)	37 (90)
Asian	0 (0)	2 (6)	1 (2)
Afro-American	0 (0)	0 (0)	0 (0)
Other	0 (0)	2 (6)	3 (7)
Family history of autoimmunity	2 (18)	9 (27)	16 (39)	0.12†
Smoking	0 (0)	14 (41)	7 (17)	0.007†
Clinical characteristics
SLEDAI 2000 score	n/a	1.5 (0–2)	2 (2–3)
SLICC criteria	n/a	3 (2–3)	6 (5–7)
EULAR/ACR criteria	n/a	6 (4–9)	18 (14–23)
Medication use
Hydroxychloroquine	0 (0)	8 (24)	35 (85)	< 0.001‡
Prednisolone	0 (0)	0 (0)	12 (29)
Methotrexate	0 (0)	0 (0)	2 (5)
Mycophenolate mofetil	0 (0)	0 (0)	9 (22)
Azathioprine	0 (0)	0 (0)	6 (15)
Autoantibody positivity
IgG
IgG anti-dsDNA	0 (0)	7 (21)	15 (37)	0.2‡
IgG anti-Ro52	0 (0)	7 (21)	4 (10)	0.21‡
IgG anti-Ro60	0 (0)	11 (32)	14 (34)	> 0.99‡
IgM
IgM anti-dsDNA	0 (0)	16 (47)	31 (76)	0.02‡
IgM anti-Ro52	0 (0)	11 (32)	10 (24)	0.61‡
IgM anti-Ro60	0 (0)	11 (32)	12 (29)	0.81‡

Data are shown as median (interquartile range) or n (%).

*Kruskal–Wallis rank sum test; †Fisher’s exact test; ‡Fisher’s exact test, HC group excluded from analysis. HC, healthy control; iSLE, incomplete systemic lupus erythematosus; SLE, systemic lupus erythematosus; SLEDAI 2000, Systemic Lupus Erythematosus Disease Activity Index 2000; SLICC, Systemic Lupus International Collaborating Clinics; EULAR, European Alliance of Associations for Rheumatology; ACR, American College of Rheumatology; IgG, immunoglobulin G; IgM, immunoglobulin M.

Figure 1. (A) Total immunoglobulin G (IgG)/immunoglobulin M (IgM) ratios, (B) IgG/IgM anti-double-stranded DNA (anti-dsDNA), (C) anti-Ro52, and (D) anti-Ro60 ratios for healthy controls (HCs), incomplete systemic lupus erythematosus (iSLE), and systemic lupus erythematosus (SLE) patients. Boxplots show median and interquartile range. **p ≤ 0.01; ***p ≤ 0.00; ns, not significant.

Figure 2. (A) Total immunoglobulin M (IgM), (B) IgM anti-double-stranded DNA (anti-dsDNA), (C) IgM anti-Ro52, and (D) IgM anti-Ro60 levels. Boxplots show median and interquartile range. HC, healthy control; iSLE, incomplete systemic lupus erythematosus; SLE, systemic lupus erythematosus; RU, FEIA response units. *p ≤ 0.05; ***p ≤ 0.001; ns, not significant.

Figure 3. Immunoglobulin M (IgM) autoantibody levels for (A) immunoglobulin G (IgG) anti-double-stranded DNA (anti-dsDNA), (B) anti-Ro52, and (C) anti-Ro60 positive (pos) and negative (neg) incomplete systemic lupus erythematosus (iSLE) and systemic lupus erythematosus (SLE) patients. Boxplots show median and interquartile ranges. RU, FEIA response units.

Figure 4. (A–D) Immunoglobulin G (IgG)/immunoglobulin M (IgM) ratios for incomplete systemic lupus erythematosus (iSLE) non-progressors and systemic lupus erythematosus (SLE) progressors over time. IgG/IgM ratios per patient are depicted as dots and connected by lines. Thick lines show median ratios per group over time.