Policy on Assays for Detecting Complement Deficiency

A. Complement Pathway Immunodeficiency

Investigations for complement deficiency will only be undertaken upon request (direct or indirect) from consultant immunologists.

Complement deficiencies will be investigated using a cascade of tests:

  • Stage 1.  Measurement of haemolytic activity (CH100/AP100) using commercial plates (Binding Site) and immunochemical measurement of C3 and C4 by nephelometry
  • Stage 2.  If impaired activity is detected, immunochemical detection of individual components will be undertaken (Ouchterlony analysis). The set CS1L will be added automatically. Tests will be set up on up to 3 plates as appropriate:

Low CH100 only   Classical pathway (C1q, C1r, C1s)

Low AP100 only     Alternative pathway (Factors B, H, I, P)

Both low                  Late components (C5, C6, C7, C8, C9)

  • Stage 3.  Quantitation of individual components (SRID) using commercial plates (Binding Site) usually only for family studies.

B. C1-inhibitor deficiency

Investigations will be carried out on requests from any user.

  • Stage 1.  Immunochemical levels of C1-inhibitor and C4 will be measured on appropriate requests
  • Stage 2.  If C4 is low, functional C1-inhibitor will be measured unless low levels of C1-inhibitor are detected immunochemically. If C4 is normal, functional C1-inhibitor will not carried out unless requested by a Consultant Immunologist

With appropriate history for acquired C1-inhibitor deficiency, paraprotein determination will be carried out.

C. Nephritic Factor

Nephritic factror will be measured on patients with low C3 and a history of glomerulonephritis or partial lipodistrophy if thought to be appropriate by the validation staff.

Page updated: 10/10/14 | Updated by: Anna McHugh