1. ¹Center of Medical Genetics, University Hospital Brussel (UZ Brussel), Vrije Universiteit Brussel (VUB), Brussels, Belgium
2. ²Laboratoire de Diagnostic Moléculaire, Service de Médecine Génétique, University Hospitals, Geneva, Switzerland
3. ³European Molecular Genetics Quality Network (EMQN), National Genetics Reference Laboratory, St Mary's Hospital, Manchester, UK
4. ⁴UnIGENe and CGPP, IBMC – Instituto de Biologia Molecular e Celular and ICBAS, Universidade do Porto, Porto, Portugal

Correspondence: Dr J Sequeiros, Universidade do Porto, UNIGENE – IBMC, R Campo Alegre 823, Porto 4150-180, Portugal. Tel: +351 22 607 4942; Fax: +351 22 600 2923; E-mail: jsequeir@ibmc.up.pt

Received 12 November 2007; Revised 20 December 2007; Accepted 17 January 2008; Published online 27 February 2008.

Abstract

The European Molecular Genetics Quality Network (EMQN) has been organizing an external quality assessment (EQA) scheme for molecular genetic testing of trinucleotide repeat mutations in the spinocerebellar ataxias (SCAs) since 2004. DNA samples were validated by at least two independent labs and two different methods. Together with mock clinical case descriptions and requests for specific SCA gene analyses, these were sent to registered participants each year. Laboratories were asked to use their routine procedures and protocols. A panel of assessors reviewed the final returns, including genotype results and reports, to assess the quality of (1) genotyping and (2) interpretation and reporting. A description of methods and raw data were also requested and were very useful for the final analysis. Altogether, during 3 years, 239 reports were received from the laboratories. Overall genotype error rate ranged 1.1–5.2%, a significant cause of concern. Scores for interpretation and reporting also showed that there is still much room for progress, although performance has improved over this period of assessment. The consequences of suboptimal laboratory practices, genotyping errors and misdiagnosis and of incorrect or incomplete interpretation and reporting have wide implications for patient lives, as well as for health management and counselling of relatives. EQA schemes are an important part of quality assurance in molecular genetic laboratories, and their use should become a routine part of laboratory diagnostic practice. Current evidence shows also that it is important that laboratories participate on a yearly basis and that this becomes mandatory for reference laboratories.