Cellular Immunology / Immunophenotyping Laboratory

Leukaemia and Non-Hodgkin Lymphoma Diagnosis and Monitoring
The laboratory provides a comprehensive service in the investigation of Leukaemia and Non-Hodgkin Lymphoma. Immunophenotyping provides additional information to morphology and cytogenetics in the diagnosis, classification and monitoring of these disorders.

 

HIV Monitoring
Immunophenotyping is used serially to monitor CD4 levels.

 

Investigation of Cellular Immunodeficiency Disease
Wrong choice of tests, especially in the paediatric setting, can mean rare cases of immunodeficiency are missed. Vital information includes type and site of infections, family history, other pathology results, X-rays and clinical features. Please refer to the Clinical Immunologists; ward or clinic referral is the ideal.

  • Immunophenotyping

Identifies numerical defects in lymphocyte subsets, inherited or acquired, and are indicated in cases with recurrent viral, fungal or mycobacterial infection.

  • Functional Leucocyte Assays

These assays are technically complex and require prior discussion with the laboratory. Abnormalities are rare, most commonly due to poor sample quality, testing during drug therapy or intercurrent infection.  Abnormal findings should always be confirmed on a second sample.  True abnormalities may need further, more specialised tests to specify the disorder.

Lymphocyte function studies are indicated in cases of recurrent viral, fungal and mycobacterial infections in whom no numerical lymphocyte defect has been defined. The investigation provides a measure of lymphocyte activation. Lymphocytes are cultured for 5 days with mitogens which mimic antigen activation.

Neutrophil function studies screen for defects in the metabolic burst and adhesion molecules and are indicated in cases with recurrent fungal or bacterial infection with a normal neutrophil count (>1x109/1).A normal result excludes major defects in neutrophil function.

 

Quantiferon Assay
The Quantiferon TB test is an interferon gamma release assay (IFGRA) for TB. The assay requires special blood tubes and sample handling requirements. The laboratory can issue guidance and sample tubes to requestors. Interpretation of the result needs to be in the context of clinical history and other laboratory and clinical investigations.  The antigens used in the test are absent from all BCG strains used and from most known non-tuberculous mycobacteria, it is possible to have a reactions to M Kansasii, M Szulgai and M. Marinarum.  If such infections are suspected, alternative test should be sought. The Quantiferon test (and other TB IFGRA) may give false negative results in immunosuppressed patients. The laboratory provides a positive control tube for all tests to ensure the validity of results. Where the positive control fails (indeterminate result) the laboratory may suggest alternative testing.
Guide to interpretation

  • A negative test does exclude the possibility of M tuberculis infection.  False negative tests can occur.
  • A positive test result should not be the only definitive  basis for making the diagnosis.
  • A positive test result should be followed by a full history and examination for suspected TB

Last updated 20/08/2014