Table 2

Investigated potential biomarkers and their correlations to disease activity

Concentration*P value†Spearman’s correlation‡
Controls
(n=322)
SLE
(n=437)
Control vs SLESLAM4
(n=437)
SLEDAI-2K2
(n=437)
PtGDA§
(n=132)
Cytokines¶
 INF-γ6.1
(4.6–9.9)
11.7
(7.0–20.2)
<0.0010.08
(p=0.08)
0.14
(p=0.005)
0.07
(p=0.4)
 IL-83.0
(2.2–4.0)
4.9
(3.1–8.7)
<0.0010.16
(p<0.01)
0.16
(p<0.01)
0.23
(p<0.01)
 IL-152.1
(1.8–2.4)
2.9
(2.3–4.1)
<0.0010.28
(p<0.01)
0.28
(p<0.01)
0.19
(p=0.03)
 Eotaxin88.4
(70.1–113.8)
133.5
(97.6–186.0)
<0.0010.07
(p=0.14)
0.04
(p=0.4)
0.14
(p=0.1)
 MCP-169.0
(55.0–85.0)
109.5
(83.0–152.5)
<0.0010.23
(p<0.01)
0.23
(p<0.01)
0.28
(p<0.01)
 MDC939.0
(764.3–1109)
844.0
(640.3–1120)
0.002−0.10
(p=0.04)
−0.17
(p<0.01)
−0.16
(p=0.06)
 MIP-1β43.8
(33.4–56.4)
72.7
(50.8–108.1)
<0.0010.18
(p<0.01)
0.20
(p<0.01)
0.20
(p=0.02)
 IL-100.3
(0.2–0.4)
0.8
(0.5–1.5)
<0.0010.20
(p<0.01)
0.27
(p<0.01)
0.18
(p=0.04)
 IL-60.6
(0.5–0.9)
1.2
(0.7–2.2)
<0.0010.23
(p<0.01)
0.24
(p<0.01)
0.30
(p<0.01))
TNF-α2.3
(2.0–2.8)
4.5
(3.1–6.2)
<0.0010.34
(p<0.01)
0.32
(p<0.01)
0.29
(p<0.01)
 IL-12/IL-23p40131.0
(99.5–179.0)
181.0
(123.0–286.0)
<0.0010.07
(p=0.12)
0.08
(p=0.11)
−0.05
(p=0.6)
 IL-16182.0
(147.0–225.0)
214.0
(152.0–287.0)
<0.0010.14
(p<0.01)
0.19
(p<0.01)
0.13
(p=0.2)
 IL-1α6.4
(3.4–11.7)
6.3
(3.2–12.8)
0.60.05
(p=0.4)
0.19
(p<0.01)
−0.06
(p=0.5)
 IL-73.7
(2.5–5.5)
5.0
(3.2–8.7)
<0.0010.11
(p=0.03)
0.16
(p<0.01)
0.10
(p=0.2)
 VEGF56.7
(40.9–81.6)
77.1
(47.7–123.5)
<0.0010.11
(p=0.03)
0.23
(p<0.01)
0.16
(p=0.07
 Eotaxin-320.8
(14.9–25.7)
24.4
(19.3–35.1)
0.00080.02
(p=0.8)
0.08
(p=0.3)
−0.01
(p=0.9)
 IP-10352.0
(258.8–479.0)
725.0
(446.0–1309)
<0.0010.19
(p<0.01)
0.23
(p<0.01)
0.27
(p=0.002)
 MCP-456.0
(41.0–80.8)
78.0
(53.8–124.0)
<0.001−0.01
(p=0.8)
−0.03
(p=0.6)
0.04
(p=0.6)
 MIP-1α12.0
(8.8–17.6)
21.5
(17.3–28.6)
<0.00010.27
(p<0.01)
0.26
(p<0.01)
0.10
(p=0.3)
 TARC54.4
(37.4–84.8)
85.3
(51.9–150.3)
<0.0010.03
(p=0.5)
0.04
(p=0.4)
0.04
(p=0.6)
Standard clinical laboratory measurements
 ESR8.5
(5-13)
19
(11-34)
<0.00010.48
(p<0.01)
0.28
(p<0.01)
0.18
(p=0.04)
 C40.21
(0.17–0.25)
0.15
(0.1–0.2)
<0.0001−0.12
(p=0.01)
−0.36
(p<0.01)
−0.10
(p=0.3)
 C31.04
(0.9–1.2)
0.88
(0.7–1.0)
<0.0001−0.10
(p<0.05)
−0.31
(p<0.01)
−0.02
(p=0.8)
 P-albumin42
(41-44)
39
(36-41)
<0.0001−0.31
(p<0.01)
−0.33
(p<0.01)
−0.42
(p<0.01)
 hsCRP0.93
(0.4–2.1)
1.7
(0.7–5.3)
<0.00010.21
(p<0.01)
0.16
(p<0.01)
0.25
(p<0.01)
 anti-dsDNA4
(4.0–4.0)
5
(4.0–19.5)
<0.00010.21
(p<0.01)
0.47
(p<0.01)
0.19
(P=0.03)
 U-albumin/creatinine0.45
(0.32–0.76)
1.11
(0.52–5.48)
<0.00010.22
(p<0.001)
0.30
(p<0.001)
0.12
(p=0.2)
  • Concentrations of investigated potential biomarkers and u-albumin/creatinine in patients with SLE and controls, their p values comparing SLE and controls and their correlations to three different measurements of disease activity are reported. Biomarkers with correlations (ρ)≥|0.25| to all three disease activity measurements are highlighted in bold. Italic numbers indicates biomarkers which are included in the respective indices.

  • *Median (25% quantile–75% quantile). Concentrations of cytokines are reported in pg/mL. Standard clinical laboratory measurements reported as ESR in mm/hour, Complement factor C4 in g/L, Complement factor C3 in g/L, plasma albumin (p-albumin) in g/L, high-sensitivity (hs) CRP in mg/L, anti-dsDNA units and urinary (u) albumin/creatinine ratio in mg/mmol.

  • †Mann Whitney U test. Not compensated for multiple testing (variables: n=26).

  • ‡Spearman’s correlation rho (p value). Spearman’s ρ>0.25 are highlighted in bold. Spearman’s ρ=|0.20–0.39| is considered as week correlation and ρ=0.40–0.59 as moderate correlation.

  • §PtGDA, Patients Global Disease Activity as determined by SLAQ.7

  • ¶The numbers of missing values are reported in online supplementary table S1 (all cytokines except IL-10, IL-6, Eotaxin-3 and MIP-1α were detected in more than 90% of cases). Data below LLOQ were treated as missing values.

  • ESR, erythrocyte sedimentation rate; LLOQ, lower limit of quantification; SLAM, SLE Activity Measure; SLAQ, Systemic Lupus Activity Questionnaire; SLE, systemic lupus erythematosus; SLEDAI-2K, SLE Disease Activity Index; VEGF, Vascular endothelial growth factor.