Table 2 Predictivity of complement in SLE flares
From: Predictive biological markers of systemic lupus erythematosus flares: a systematic literature review
Complement fraction(s) | Number of patients (n) | Findings | Study |
|---|---|---|---|
Positive results | |||
 C3, C4 and CH50 | 57 | Increased incidence of exacerbation in patients with decreased level of C3 or CH50 | Tomioka et al., 2008 [7] |
 C3 and C4 | 562 | Low C3 level (< 900 mg/L) was an independent predictor of a severe SFI flare | Petri et al., 2013 [9] |
 C3 and C4 | 299 | Low C3 and C4 were risk factors for a later A or B flare in the mucocutaneous, renal and haematologic systems | Petri et al., 2009 [10] |
 C3 | 32 | Low baseline serum C3 (< 900 mg/L) was a predictor for shorter time to flare | Ng et al., 2007 [36] |
 C3 and C4 | 46 | Baseline C4 titres were low (< 10 mg/dl) in a significantly higher percentage of relapsing patients | El Hachmi et al., 2003 [8] |
 C3 and C4 | 145 | C4 level (< 11 mg/dl) was a significant prognostic factor for renal flares | Illei et al., 2002 [35] |
 CH50 | 60 | CH50 level was an independent predictor of lupus flares | Viallard et al., 2001 [38] |
 C1q, C3, C4, C5 and C9 | 143 | Decrease of C4, followed by decreases of C1q and C3 levels (< 40% of normal values), started 25 to 20 weeks before renal involvement | Swaak et al., 1986 [12] |
 C3a, C5a, C3 and C4 | 40 | C3a levels rose significantly (>200 ng/ml) 1–2 months prior to flare | Hopkins et al., 1988 [32] |
 C3 | 189 | Persistently low C3 level was a predictor of nephritic renal flares | Mok et al., 2004 [23] |
 C1q, C3, C4 | 27 | When patients were clinically active, mean values of C1q, C4 and CH50 were the lowest obtained for these markers | Lloyd and Schur, 1981 [19] |
 C3 and C4 | 71 | Lower C4 levels (< 12 mg/dl), but not C3 levels, significantly predicted renal flares | Birmingham et al., 2010 [37] |
 C3 and C4 | 218 | For renal flares: low C3 (0.5–0.74 g/L), sensitivity 34.8%, specificity 63.1%; low C4 (0.1–0.13 g/L), sensitivity 19.4%, specificity 79% | To et al., 2011 [27] |
 C3 and C4 | 218 | For severe flares: low C3 (0.5–0.74 g/L), sensitivity 29.2%, specificity 63%, PPV 2.3%, NPV 96.7%; low C4 (0.1–0.13 g/L), sensitivity 19.2%, specificity 79%, PPV 2.8%, NPV 96.0% | To et al., 2011 [28] |
 C3, C4, CH50 and complement split products: Ba, Bb; C4d; SC5b-9 | 86 | Most sensitive marker of flare: elevated C4d (> 8.5 mg/ml). Highest specificity and greatest predictive value for flare: elevated Bb (> 1.2 mg/ml) | Buyon et al., 1992 [33] |
Negative results | |||
 C3, C4 and C1q | 202 | Fluctuations were poor predictors of exacerbations | Esdaile et al., 1996 [20] |
 C3 and C4 | 53 | Decreasing complement levels did not precede changes in disease activity | Ho et al., 2001 [34] |
 CH50 | 120 | No consistent association of complement titre with flares in the subsequent year | Mirzayan et al., 2000 [6] |
 C3, C4 and CH50 | 73 | No difference between patients who flared and patients who did not | Walz LeBlanc et al., 1994 [31] |