First- and Second-Trimester ADAM12s in Down Syndrome Screening

To the Editor: ADAM12s1 (a disintegrin and metalloprotease 12s), a placenta-derived glycoprotein involved in tissue growth and differentiation, has been shown to be an early screening marker for trisomy 21 before the 10th week of gestation (1) and a potential second-trimester marker. A recent report suggested that measurements of a serum marker in both the first and second trimesters (repeated measures) could provide better performance than single measurements in either trimester (2). We sought to demonstrate the potential value of such repeated measures of ADAM12s for the screening of Down syndrome. A cohort of 7194 women underwent integrated biochemical screening before amniocentesis at the Department of Obstetrics and Gynecology, University of Messina, between December 1, 2006, and March 31, 2009. After collection, the maternal serum samples were stored at −80 °C. We selected paired first- and second-trimester samples from 19 Down syndrome pregnancies (cases) from frozen storage for ADAM12s measurement. Of the Down syndrome cases, 14 were identified from amniocentesis results, and 5 were identified at birth. Two of the latter were excluded owing to maternal smoking and the unknown potential effects of smoking on maternal ADAM12s values in serum. ADAM12s also was measured in frozen samples from 562 unaffected pregnancies matched for gestational age (GA). GAs ranged between 7 and 10 completed weeks in …