Buku Medicine


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Immunoglobulin - low

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Serum electrophoresis

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Lymphocyte subsets

This test measures the percentage and absolute numbers of different lymphocyte subsets.


  1. Suspected B cell deficiency/antibody deficiency
  2. Suspected combined Immunodeficiency
  3. Patients with HIV
  4. Genetic diseases like DiGeorge syndrome

It is performed using flow cytometry. This test identifies T cells (CD4 and CD8), B cells (CD19) and Natural Killer cells (CD56) based on the cell surface markers.

These tests need to be interpreted by age-appropriate reference ranges.

Sample needed – Fresh EDTA sample, 5 – 10ml.



Types of allergy test

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Complement levels

Quick tip; There can be false ‘normal’ C3/C4 results in patients with e.g SLE, if there is C3/4 consumption due to an infective/inflammatory insult

Measurement of C3 and C4 components of complement allows analysis of both the classical and alternative complement pathways. C3 and C4 proteins are acute phase proteins and may therefore be normal at times of rapid complement consumption; assessment of C3 breakdown products in this scenario is advised.

Indications for testing:

  • Complement deficiency [tested in combination with the CH50/AP50 function test]
  • SLE
  • Anaphylaxis [anaphylotoxins C4a and C5a]
  • Hereditary angioedema [tested in combination with C1-esterase inhibitor and functional C1-esterase inhibitor]
  • Acquired angioedema [with C1q level]
  • Monitoring SLE and immune complex disease (infective endocarditis, serum sickness)
  • Atypical haemolytic uraemic syndrome
  • Cryoglobulinaemia



*Complement levels need to be interpreted in the context of the clinical setting, as pre-disease levels are often unknown*

Low C4, normal C3:

  • Genetic deficiency [C4 allele copy number for C4 null alleles]*
  • SLE (active) -check C3 breakdown products
  • Hereditary angioedema
  • Type II cryoglobulinaemia
  • Eclampsia

Low C3, low C4:

Consistent with classical pathway activation and active inflammation

  • Sepsis
  • SLE (active)
  • Infective endocarditis
  • Rheumatoid arthritis

Normal C4, low C3:

Consistent with alternative pathway activation

  • Post-streptococcal glomerulonephritis
  • C3 nephritic factor
  • Gram negative sepsis

High C3, high C4:

  • Acute phase response

*C4 null alleles are common and affect the baseline level of C4; it is not possible to use C4 levels as a marker of SLE activity without knowing how many null alleles are present.