EMQN Best Practice Guidelines for molecular and haematology methods for carrier identification and prenatal diagnosis of the haemoglobinopathies

Abstract

Haemoglobinopathies constitute the commonest recessive monogenic disorders worldwide, and the treatment of affected individuals presents a substantial global disease burden. Carrier identification and prenatal diagnosis represent valuable procedures that identify couples at risk for having affected children, so that they can be offered options to have healthy offspring. Molecular diagnosis facilitates prenatal diagnosis and definitive diagnosis of carriers and patients (especially ‘atypical' cases who often have complex genotype interactions). However, the haemoglobin disorders are unique among all genetic diseases in that identification of carriers is preferable by haematological (biochemical) tests rather than DNA analysis. These Best Practice guidelines offer an overview of recommended strategies and methods for carrier identification and prenatal diagnosis of haemoglobinopathies, and emphasize the importance of appropriately applying and interpreting haematological tests in supporting the optimum application and evaluation of globin gene DNA analysis.

Assembly and evaluation of an inventory of guidelines that are available to support clinical hematology laboratory practice

“…A total of 68 guidelines (one with an addendum) pertaining to clinical hematology laboratory practice were identified that had been posted or published in the public domain (Table ) , after adjudication of the documents found through searches of the published literature and websites. The organizations that had generated these guidelines included American Association of Clinical Chemistry (AACC) , British Committee for Standards in Haematology (BCSH) , College of American Pathologists (CAP) , Clinical and Laboratory Standards Institute (CLSI), European Molecular Genetics Quality Network (EMQM), European Society for Clinical Cell Analysis (ESCCA) , International Council for Standardization in Haematology (ICSH) , Institute for Quality Management in Healthcare (IQMH; formerly Quality Management Program – Laboratory Systems [QMP‐LS]) , ISTH , International Clinical Cytometry Society (ICCS) , International Society for Laboratory Hematology (ISLH) [50], North America Specialized Coagulation Laborato...…”

“…Only one guideline had been developed through consensus of the laboratories performing the test . A review of the authorship on different guidelines indicated that quite a few individuals had engaged in guideline development for different organizations.…”

“…We also postulated that the inventory of guidelines from different organizations would increase guideline awareness and use worldwide and that it would help organizations interested in guideline development to identify gaps in what current guidelines cover. We observed that a limited number of international and regional organizations, alone or in partnership, had generated the current guidelines that are relevant to clinical hematology laboratory practice . With the exception of CLSI documents, guidelines were generally available free of charge, mainly through open access publication or posting.…”

Screening non-deletion α-thalassaemia mutations in the HBA1 and HBA2 genes by high-resolution melting analysis

“…Carriers of α-thalassaemia are initially implicated based on haematological and biochemical tests, but definitive diagnosis of suspected carriers (and patients) requires DNA analysis [4].…”

ICSH recommendations for assessing automated high‐performance liquid chromatography and capillary electrophoresis equipment for the quantitation of HbA2

“…The red cell hematology should be that of a chronic microcytic state with moderate erythrocytosis relative to the hemoglobin concentration (unless folate deficient) and not responding to appropriate iron therapy. Although ‘HbA 2 levels above 3.5% are considered the standard cut off value , above which heterozygosity for β‐thalassemia is indicated,’ a HbA 2 of 4% is usually considered a safe threshold to diagnose β‐thalassemia trait with most carriers having levels of 3.8% or above; levels below 3.0% are usually considered safe to exclude cases of the common High HbA 2 β‐thalassemia trait if normocytic and normochromic as most people who are not carriers have a HbA 2 less than 3.2%. However, even with greater accuracy and less imprecision, the use of HbA 2 testing alone will not be able to exclude cases of borderline or ‘Normal HbA 2 ’ β‐thalassemia or combinations of β‐ and δ‐thalassemia where a microcytic, hypochromic anemia with a normal HbA 2 might be mistaken for α‐thalassemia.…”