Diagnosis of leukaemia involves a number of pathology disciplines, followed by further procedures to identify the type of leukaemia it may be. Next-generation sequencing does offer benefits for the diagnostics, but comes with its own obstacles. Vela Diagnostics has specifically developed its Sentosa NGS system to meet the requirements of routine molecular diagnostics applications.

Leukaemia is the 11th most common cancer worldwide, claiming more than 260,000 lives every year. There are four main types of leukaemia, which are based on the cell origin and the acuity of the disease: chronic lymphocytic leukaemia (CLL), which is the most common; acute lymphoblastic leukaemia (ALL); chronic myeloid leukaemia (CML); and acute myeloid leukaemia (AML). There are also several less-common types.

With leukaemia being a very heterogenic group of diseases, diagnosis involves a number of different pathology disciplines. In most symptomatic cases, it is primarily diagnosed via abnormal results on a full blood count, followed by a bone-marrow examination, but various additional techniques are used to further classify the type of leukaemia and help refine the diagnosis, establish the prognosis and determine the treatment.

Finding the sub-form

A comprehensive analysis of leukaemia-causing genetic changes is of utmost importance, since the exact sub-form is required to assess the prognosis and, with that, the course of patient management. The diagnosis and classification of AML in particular requires detailed genetic information in addition to clinical, morphological and immunophenotypic findings.

The current 2008 World Health Organization AML classification system defines several distinct sub-types based on the presence or absence of genetic abnormalities. Molecular analyses are also needed in CML and ALL to detect the fusion gene counterparts of chromosomal translocations, and monitor the treatment and course of the disease.

With scientific advancements enabling a better understanding of these interactions, the findings allow ever-more personalised therapeutic approaches. These are then selected according to the presence or absence of genetic aberrations such as mutations, copy number alterations and gene translocations. A quantitative assessment of gene mutations can also be useful for prognostication or to monitor minimal residual disease.

Molecular methods

Several different molecular methods are used to obtain detailed genetic disease information in leukaemia patients. The most commonly used, such as PCR, fluorescence in-situ hybridisation and array-based methods, also show a range of drawbacks. To get a comprehensive analysis, a combination of different tests is needed. This approach requires large amounts of DNA, and compilation of results into an integrated clinical report is often difficult and time-consuming.

Compared with these methods, next-generation sequencing (NGS) shows clear benefits for leukaemia testing by analysing large numbers of genes in a single test and allowing for simultaneous detection of deletions, insertions, base substitutions, copy number alterations and translocations. However, until recently, NGS was only used for research purposes. Use for diagnostic purposes was considered difficult, mainly due to a lack of standardisation, automation, sample tracking, and the need for advanced molecular biology and informatics skills.

Vela Diagnostics has developed a solution to overcome these obstacles. In the latter half of 2014, it launched the Sentosa NGS system, specifically developed for the requirements of routine molecular diagnostics applications*. The system needs only minimal amounts of sample material. It automates sample extraction and library preparation, and thus reduces hands-on time, minimises the need for test repeats and offers high reproducibility. To ensure optimal sample traceability, the system offers IT connectivity and optional laboratory information systems interfacing. The reporting tool provides automated data analysis and user-friendly report compilation.

After the successful development of a range of solid tumour assays*, the next test that will be launched later this year is the Sentosa SQ Leukaemia Panel*, targeting a total of 325 amplicons and 4,603 mutations in 49 different genes. This assay will provide an invaluable tool to cover all important genetic aberrations, and thus allow for quick and reliable determination of the best treatment for leukaemia patients and will finally allow NGS to make its way into routine leukaemia diagnostics.

* Product availability is country dependent, not available in the US.