The Clinical and Laboratory Standards Institute (CLSI) has published 'Maternal Serum Screening; Approved Standard - Second Edition (I/LA25-A2)'.
The document addresses the steps required to provide reliable screening and reporting using examples of serum markers in common use (AFP, hCG, uE3, inhibin A, PAPP-A).
The revision of I/LA25 was spurred by the emergence of new options for screening techniques since its 2004 publication, including testing in the first trimester, in the second trimester, and testing that combines both the first and second trimester.
First-trimester screening is emphasised, in which serum markers PAPP-A and hCGa are used, and for which the main ultrasound marker is nuchal translucency.
Prenatal screening for serious foetal abnormalities has made significant advantages since the 1970s, when laboratories began using maternal serum alpha-fetoprotein as a screening test for open neural tube defects.
I/LA25 reflects these developments by specifying requirements and recommendations for maternal serum aspects of prenatal screening for neural tube defects and trisomy 21, while incorporating ultrasound measurements to ensure that screening methods and quality control procedures are carried out to a high standard.
Manufacturers, diagnostic laboratories, regulatory agencies, and public health authorities involved in providing or regulating prenatal screening services to evaluate pregnancies and the risks of foetal disease will benefit from the use of I/LA25, which serves as a learning tool across multiple disciplines.
The standard is intended to present necessary considerations of the pre-analytical, analytical, and post-analytical (pre-examination, examination, and post-examination) processes of maternal serum screening.
At the same time, the document intends to strike a balance between being sufficiently specific but not too prescriptive, allowing laboratory directors to use their professional judgement in setting policy.
In this way, I/LA25 will help to ensure test reliability, including risk calculation, outcome evaluation, and the accuracy of information management.
If properly applied, the five biochemical determinations and these risk calculations can contribute constructively to the field of prenatal screening and to the welfare of pregnant women and the foetus.
