External quality assessment of maternal serum screening schemes. A view from UK NEQAS

AUTORI

ABSTRACT

Maternal serum screening schemes for prenatal detection of conditions including Trisomy 21 (Down syndrome) and neural tube defects (spina bifida) are now well-established worldwide. These programs rely on biochemical testing with the aim of identifying pregnancies that may be at risk of these conditions prior to undertaking more complex and definitive investigations. This places major responsibility on laboratories to ensure that analytical results are accurate. Well-designed external quality assessment (EQA) schemes provide a means of assessing how well analytical results compare with those of other laboratories using the same methods as well as assessing how well methods agree when used in routine laboratories. EQA schemes can also provide an indication of interpretation of the outcome of biochemical screening tests, which are generally reported to clinicians in terms of risk rather than analytical results. These risks are calculated using method-specific algorithms which require input of the analytical results and other parameters including maternal age and weight, length of gestation and ultrasound measurements of the foetus. Providing these clinical details with specimens issued and requesting that EQA participants submit their calculated risks and recommendations for action for each specimen, enables assessment of interpretative as well as analytical aspects of service provision for individual participants. Here we report on how the UK National External Quality Assessment Service (UK NEQAS) monitors such performance

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