The basic techniques used in diagnosing haematological
malignancies include:
Morphology: This is the examination of a bone
marrow aspirate under a microscope and is the first stage of
evaluating a patient suspected of a haematological malignancy. This
result is evaluable within minutes of a sample being taken allowing
rapid evaluation for patients requiring urgent clinical
intervention eg acute leukaemia. Occasionally, as in the case of
myeloma, the diagnosis can be made easily without the need for
further investigation of the bone marrow. Usually however further
investigation of the bone marrow is required.
Histology/Immunohistology: This is the
examination of tissue that has been fixed, finely sectioned and
stained. This process can be applied to any tissue but typically
this is performed on bone marrow trephines and lymph nodes. In
cases of Aplastic anaemia the diagnosis is clear from the greatly
reduced cellularity.
Flow cytometry: This allows rapid
identification (within 1hour) and quantification of subpopulations
of cells in suspension through assessment of light scatter
properties and antigen expression. Samples are labeled with
fluorescently-tagged antibodies specific for select cell antigens.
The antibodies used are tailored to specimen type, clinical history
and suspected diagnosis. Our cytometers are capable of
simultaneously examining up to 8 different antigens. This offers a
very high level of sensitivity and allows for the identification of
abnormal populations at diagnosis as well as minimal residual
disease testing post therapy with the clinical information, results
from morphology and flow cytometry rapid decisions can be taken on
which further diagnostic investigations are required avoiding
unnecessary tests and ensuring an efficient management pathway for
the patient.
Applications: Immunohistochemistry is a
technique for the demonstration of antigens in histological tissue
sections and has the advantage of providing immunophenotypic
information with preserved spatial organisation of labelled and
unlabelled cells. This is critically important for example in the
diagnosis of lymphomas.
Molecular diagnostics: This
uses techniques such as PCR and RT-PCR have an increasing role
in haematological diagnoses. These highly sensitive assays can
detect abnormalities associated with specific diseases and allow in
many settings the detection and monitoring of Minimal Residual
Disease. Urgent results are available within 48-72
hours.
Cytogenetics: This is an important
investigation in certain settings and where appropriate samples are
sent to the regional laboratories either at Southmead
Hoapital, Bristol or Salisbury. These investigations
take approximately one week for FISH and three weeks for
standard cytogenetic analysis.
Applications:
· Jak 2, Mpl, Kit mutation detection in Myeloproliferative
Neoplasms
· Prognostic markers in Acute Leuakaemia eg FLT-3 and NPM-1
mutations
· Qualitative detection of important chromosomal abnormalities in
AML eg inv 16, t(8;21), t(15;17)and t(9;22)
· Quantitative BCR-ABL monitoring in CML and ALL
· Quantitative NPM1 monitoring in AML
· Detection of t(11;14) and t(14;18) mutations seen respectively in
Mantle Cell Lymphoma and Follicular Lymphoma
· T cell and B cell clonality
· IgVH mutational analysis in CLL
· Non-malignant uses eg FVL, Prothrombin mutations, and
Haemochromatosis diagnosis.
