Table 4 Methods for assessment of plasma and membrane complement proteins and screening for anti- factor H antibodies
Plasma or membrane complement Proteins | Plasma concentration (mg/L) (- 2 to + 2 SD) or membrane expression | Technique | Laboratory | Interpretation |
|---|---|---|---|---|
C3 | 660-1250 | Nephelometry | Basic complement screen | Severe complement consumption through the alternative pathway indicated by very low plasma levels of C3 and CFB. Frequently, there is only an isolated moderate decrease of C3 level with normal CFB level |
CFB | 93-380 | Nephelometry | Specialized diagnostic | Â |
CFH | 330-680 (no international standard) | ELISA | Specialized diagnostic | CFH or CFI less than 60% of normal are compatible with quantitative deficiency |
CFI | 40-80 (no international standard) | ELISA (or radial immunodiffusion) | Specialized diagnostic | Â |
Anti-CFH Ab | Screening | ELISA | Specialized diagnostic | The title is expressed in Arbitrary Units (AU) |
MCP | Mean fluorescent intensity (MFI) | FACS (a) with anti- MCP phycoerythrin -conjugated antibodies | Specialized diagnostic | No MCP expression is detected in patients with homozygous MCP deficiency. The MFI in patients of heterozygous MCP deficiency is around 50% of the normal range |