A risk calculator for Down syndrome according to ultrasound markers

As published by Greggory R De Vore, MD, Fetal Diagnostic Center of Pasadena, Pasadena, California, USA Programme written by DJR Hutchon copyright Requires Internet Explorer 4.0 or above (or eqivalent) for calculator to work. Year 2000 compliant

INSTRUCTIONS: Enter the findings from the ultrasound, the prior risk and press calculate button. If the prior risk is simply background age risk, the calculator will calculate this using the Hecht and Hook formula, if the date of birth and the date of scan are entered. You are advised to look carefully at the paper by Gregroy R Devore. The results are only valid for women aged 34 years or older and/or with an abnormal maternal serum screening. Also incorporates the data of Huggon et al for isolated echogenic foci of the fetal heart. Ultrasound Obstet Gynecol 2001;17:11-16

Down risk assessment - US date system (MM/DD/YYYY)

Enter date of birth if known Enter date of scan (only if date of birth entered)
ENTER PRIOR RISK 1 in (If not simply based on age)
Risk (at about 20 weeks gestation) according to age is 1 in
Full detailed anomaly scan Anomaly scan with limted cardiac marker no anomaly scan
Head ultrasound markers present - CNS Nuchal skin fold Choroid plexus cyst
Chest abnormality present - VSD Right to left disproportion in heart
ISOLATED heart echogenic focus(all other abnormlities checked will be ignored)
Pericardial effusion Tricuspid regurgitation
Abdominal abnormality present - Hyperechoic bowel Pyelectasis

LR = POSTERIOR RISK = 1 in

This calculator is for educational use. It is believed accurate but no responsibility for accuracy of the results is accepted by the author. David J R Hutchon BSc, MB, ChB, FRCOG Consultant Obstetrician, Memorial Hospital, Darlington, England.
Comments and suggestions are welcome and will be included in the comments section.

To E-MAIL me CLICK HERE TO SEND COMMENTS AND PLEASE REGISTER YOUR NAME AND E-MAIL IF YOU INTEND TO KEEP AN OFF-LINE COPY at DJRHutchon@Postmaster.co.uk

If the prior risk is based on nuchal translucency there is likely to be an unknown interaction with a nuchal skin fold of 6mm or more. In De Vere's series there was no coorelation between choriod plexus cysts and the incidence of Down syndrome. By going to the source code the LR's can be changed according to any local or emerging alternative liklihood ratios. Although the calculator ignores the risks of other abnormalities checked when the echogenic heart is box is checked, it is not implied that these other abnormalities do not affect the LR but simply that the degree of interaction is unknown. If other abnormalities are seen it is best to ignore the echogenic heart even when this is apparent.
REFERENCES
Devore G R. Trisomy 21 : 91% detection rate using second-trimester ultrasound markers. Ultrasound in Obstetrics and Gynecology 2000; 16:133-141
Hecht C A & Hook EB the imprecision in rates of Down syndrome. (1994) Prenatal Diag 14:729-738
Huggon I C, Cook A C, Simpson J M, Smeeton N C, and Sharland G K. Isolated echogenic foci in the fetal heart as a marker of chromosomal abnormality. Ultrasound Obstet Gynecol 2001;17:11-16

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About the author
All my calculators will work OFF-LINE if you wish. You are welcome to copy them over. But check for updates from time to time!

LINKS TO OBGYN.NET and Fetal medicine Unit, St Georges, London and Joseph Woo's Ultrasound

Go to OBGYN.net paper on proposal for valid customised charts generation ("Back to the future for Hermanni Boerhaave" published by OBGYN.NET)
Hutchon DJ, et al. Clinical interpretation of ultrasound biometry for dating and for assessment of fetal growth using a wheel and chart: is it sufficiently accurate? Ultrasound Obstet Gynecol. 1999 Feb;13(2):103-6. Copyright 2001, DJR Hutchon. Restricted use is hereby granted (personal OK) so long as this code is not *directly* sold and the copyright notice is buried somewhere deep in your HTML document.