The development of performance assessment tools to improve the quality of diagnosis and monitoring of haemoglobinopathy disorders

De La Salle, Barbara John (2018) The development of performance assessment tools to improve the quality of diagnosis and monitoring of haemoglobinopathy disorders. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

The haemoglobinopathies are complex inherited disorders of haemoglobin synthesis. Although carriers are generally asymptomatic, homozygous or compound heterozygous inheritance of globin gene mutations may result in severe conditions, identified as a major burden of disease worldwide. The main means of control of the conditions is by carrier screening using specialist laboratory testing, allowing individuals an informed reproductive choice. UK NEQAS Haematology provides a comprehensive external quality assessment service for the haemoglobinopathies and is in a unique position to provide an overview of laboratory performance. The increased emphasis on laboratory quality and a shift in the profile of the participating laboratories from mainly UK-based to more than half non-British Isles in the past decade are drivers for continued improvement in performance assessment methods. The project looked at aspects of performance of both UK NEQAS and the participants. A review of historical quantitation data for haemoglobin (Hb) A2, the standard biomarker for beta thalassaemia carrier identification, showed there remains a need for standardisation between methods of analysis. The survey material distributed for testing was examined to exclude commutability and stability as confounding factors in performance assessment. Changes to Hb A2 performance scoring have been suggested including the identification of one-off analytical EQA errors that could represent misdiagnosis of a beta thalassaemia carrier. In newborn screening, a difference was seen in the sensitivity of different analysers at the low levels of adult haemoglobin (Hb A) seen in a newborn infant with homozygous beta thalassaemia. A significant difference in performance in result interpretation was seen between English NHS laboratories and those outside the British Isles. The scheme should extend performance management in interpretation to all laboratories including the non-British Isles group, to ensure that the scheme remains credible to participants and fulfils its remit to improve performance wherever patients are tested. This will however require the scheme to develop the EQA data capture methods better to reflect current laboratory practice.