OBGYN.net
Conference Coverage
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"Screening for Down's Syndrome"
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| 3/12 2001 - The afternoon scientific session on Ob anomalies was well-attended. The topic of the day was the use of Ultrasound as a screening tool for Down's Syndrome. Two presentations from Dr. Nyberg's group once again demonstrated the utility of sonographic "markers" to stratify risk. Since ultrasound markers and maternal serum screening are independent, the combination of ultrasound and biochemistry may prove a better testing scheme than either alone. This has been shown for the first trimester and Dr. Nyberg showed that this holds true for the second trimester as well. They also noted that fetal pyelectasis, found in about 5% of normal fetuses, did not show significance as a risk for Down's. Some markers, such as nuchal skin thickening, seems to vary in significance with gestational age, similar to the relationship of nuchal translucency in the first trimester. Dr. Souter, working with Nyberg's group, remarked that a "magic number" cut-off may miss some cases of Down's. Dr. DeVore presented a stepwise testing scheme of serum screening followed by ultrasound in the high and moderate risk groups. Allowing several levels of sensitivity, this stepwise program theoretically seems more cost-effective and resulted in fewer procedure-related losses than utilizing either age alone or age and serum screening. Dr. Egan's group seemed to echo these findings in both the pregnancies having an increased maternal age-related risk and those women with a negative triple screen. Dr. Carreno then presented data showing that certain markers, most notably echogenic intracardiac focus, may not have the same significance in certain ethnic groups - specifically Hispanics and Asians. Dr. Kovac's group then demonstrated the effect of ethnicity on femur length. The use of ultrasound as a screening tool for aneuploidy is currently a matter of concern for the ultrasound community. The relationship of sonographic markers and Down's syndrome was first demonstrated in populations with high prevalence. Therefore, such a finding would have increased significance. Over the last decade, the number of individual markers has proliferated and their use has expanded into the low risk populations. A recent editorial by Roy Filly in the JIUM suggested that this practice may be a misuse of the technology. Additionally, two weeks ago in the JAMA, Smith-Bindman et al suggested that the performance of these markers may not be a effective as previously thought. Practitioners opine that now that this genie is out of the bottle, the omnipresent specter of lawsuit for failure to diagnose Down's syndrome, forces them to report all abnormal findings. A consensus development conference on the proper use of ultrasound for Down's syndrome screening will be held later this year. One can only hope that perhaps some firm direction in this contentious area will result. Would you like to comment on this article? This link will open your email program with the subject line completed and the url of the article you are commenting on in the body of your message. |