[Maternal serum screening for Down's syndrome: a user's club experience]

Screening of Down syndrome using maternal serum markers requires specific quality management. We report here a user's club experience (Down's Club Abbott) in surveying performances of AxSYM total beta hCG and AFP reagents combined to Maciel software. Regular analysis was carried out during three years (1998 to 2000). Values from five laboratories were collected to achieve calculation of medians for each parameter, multiple of the medians and initial positive rate (cut-off of 1/250 established in France). The large size of the observed population (3,1020 women during the studied period) increased the performances of statistical evaluations. In July 1999, five months after a change in reagents leading to new medians, these latter were recalculated in agreement with the manufacturer. Our experience exhibits that only the concomitant analysis of all parameters (medians, multiple of medians and initial positive rate) can allow the monitoring of a potential drift (bound or not to reagents). Moreover, such user's clubs enhance the individual quality management of the laboratories and allow a good follow-up of the performances of the testing in time.