The value of complement measurements in the assessment of lupus activity

Abstract

The complement system was studied prospectively in 29 patients, predominantly renal (25), with systemic lupus erythematosus (SLE) to examine the value of complement assays in the distinction between active and inactive disease. Disease activity was evaluated primarily by clinical, biochemical and histological parameters which were obtained at the time of assessment. Fourteen patients had active disease, as assessed by clinical and laboratory criteria. C1q, C4, C4a, C2, C3, C3a, C5, total haemolytic activity (CH50) and complement inhibitors were measured in each patient. The ratios of C4a:C4 and C3a:C3 were also calculated. Values for all components except C5 were different between control subjects and active patients while only CH50 was different between inactive patients and controls. All parameters except C4a:C4 and C5 were different between active and inactive patients. There was a highly significant difference in the number of active patients with reduced levels of C2, C3 and C3a:C3 compared to inactive patients (i.e. p less than 0.001) whereas lesser or no difference was observed for other parameters. The concentration of complement inhibitors was elevated in both groups. We conclude that, among readily available complement parameters, C2 and C3 provide the best assessment of disease activity in patients with SLE.

Reference distributions for complement proteins C3 and C4: A comparison of a large cohort to the world's literature

“…A total of 50 publications were identified that contained information on C3 in apparently healthy individuals . Thirty-six articles had enough data to calculate central estimates (8,9,(11)(12)(13)(14)16,17,19,20,(22)(23)(24)26,28,29,(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)44,46,48,49,(52)(53)(54)(55)(56). Eighteen studies supplied sufficient information for calculating the reference intervals (8,10,11,13,14,17,(21)(22)(23)(24)27,37,40,49,…”

“…A total of 32 publications were identified that contained information on C4 in apparently healthy individuals (7,(9)(10)(11)(12)16,17,19,20,(22)(23)(24)(25)(26)(27)(28)(29)(30)32,(34)(35)(36)(37)(38)(40)(41)(42)(43)(44)(45)(46)(47)(49)(50)(51)(52)(53)(54)(55), and supplied sufficient information for calculating central estimates (9,11,12,16,17,19,20,22-24, 26-29, 32,34-38,40-42,44,46,47,49,51-55). Thirteen articles supplied sufficient information for calculating the reference intervals (20,(22)(23)(24)27,28,30,40,49,…”

Complement haemolytic activity (classical and alternative pathways), C3, C4 and factor B titres in healthy children

“…In fact, CP lytic activity, usually evaluated by measurement of CH50 units and the concentrations of C3, C4 and factor B, are the only complement parameters available in many laboratories. Furthermore, the usefulness of measuring C3 and C4 levels to assess disease activity in patients with systemic lupus erythematosus has recently been highlighted (17,(19)(20)(21).…”

The metabolism of C9 in normal subjects and in patients with autoimmune disease

“…In contrast to C9, earlier components of the complement cascade such as C3 and C4 tend to be in reduced concentration in the presence of a pathological activator such as antigen/antibody complexes [10,11]. Previous studies have shown that several mechanisms underlie this reduced concentration.…”