Performance of second-trimester maternal biochemistry screening (quadruple test vs. triple test) for trisomy 21: An Indian experience

BACKGROUND & OBJECTIVES: Down syndrome (DS) is one of the most common causes of developmental delay. In India, there is no protocol for prenatal screening of DS. Second-trimester biochemical screening is still being done by triple test. Quadruple test is with better sensitivity and specificity but is not advised routinely. So, the objective of this study was to evaluate the sensitivity and accuracy of the second-trimester screening (quadruple test with genetic sonogram) for trisomy 21 as compared to biochemical testing. METHODS: This retrospective observational study was carried out in a Fetal Medicine Centre to analyze the odds of being affected with DS, given a positive risk (OAPR) upon screening in the quadruple test; triple test and quadruple test plus a genetic sonogram for high-risk singleton pregnancies (in view of advanced maternal age; an anomaly scan showing some abnormality, etc). RESULTS: 3175 high-risk singleton pregnancies were screened for trisomy 21. 394 women underwent amniocentesis on the basis of triple test, quadruple test or quadruple plus genetic sonogram positive. 17 foetuses were diagnosed to have DS. The quadruple test was found to have a higher OAPR as compared to the triple test (1:30.1 as compared to 1: 40.2). Quadruple test plus the genetic sonogram was found to have the highest OAPR of 1:6. INTERPRETATION & CONCLUSIONS: Best screening for trisomy 21 is provided with quadruple test with genetic sonogram which can lower the rates of unnecessary amniocentesis in high-risk population.