Correlation between maternal serum biochemical markers with karyotyping for prenatal screening of foetal chromosomal abnormalities

Background: Prenatal screening for chromosomal abnormalities can be done by biochemical screening tests like dual marker test (DMT), triple marker test (TMT) and quadruple marker test (QMT). It is important to identify ideal screening test among them which best correlates with result of karyotyping which is confirmatory test of foetal chromosomal abnormalities. This helps to decrease need for invasive prenatal tests for foetal karyotyping. This study aims to evaluate sensitivity, specificity, diagnostic accuracy and correlation of DMT, TMT, and QMT with results of karyotyping.Methods: Retrospective observational study was conducted in tertiary care maternity hospital over one year- 1st January 2015 to 31st December 2015. Women with singleton pregnancy undergoing DMT, TMT or QMT were included.Results: Of the 529 women screened by biochemical marker tests, 462 (87.33%) were screen negative and 67 (12.66%) women were screen positive. In 56 women, it was false positive (83.58%) and in 11 women true positive (16.41%). In 461 women the test results were true negative (99.78%), but in one case, result was false negative (0.21%).  3/11 (27.27%)women with foetal chromosomal abnormalities were primigravidae. 4/11 (36.36%)women were below 35 years. DMT and QMT had higher sensitivity (both 100%) and specificity (90.00% and 93.18% respectively) than TMT (sensitivity 80% and specificity 82.61%). Positive likelihood ratio (LR+) was 1.00 in DMT. Diagnostic odds ratio was highest with DMT (DOR=115.11) and best correlated with karyotyping results (coefficient of correlation 0.4).Conclusions: Universal screening of antenatal women, irrespective of their age and parity is suggested. DMT has highest diagnostic value and best correlation with the results of karyotyping. Hence the dual marker test can be considered to be better test for screening for aneuploidy