### Abstract

Objectives-The purpose of this study was to compare the screening efficiency for Down syndrome using likelihood ratios versus logistic regression coefficients. Methods-We conducted a retrospective study of women at increased risk for Down syndrome referred for a second-trimester genetic sonogram. Likelihood ratios were calculated by multiplying the risk ratio from maternal serum screening by the likelihood ratios of sonographic markers. Logistic regression coefficients were calculated using a formula derived from β coefficients generated from a multivariable logistic regression model. The screening efficiency of both methods was tested in an independent population of patients. The McNemar test was used to compare the predictive ability of the two methods. Results-In the validation population, the use of likelihood ratios had an area under the receiver operator characteristic curve of 0.90 for Down syndrome detection, whereas the use of logistic regression coefficients had an area under the curve of 0.86. Adopting a risk cutoff point of 1/270, the sensitivity of likelihood ratios was 77.4% (95% confidence interval [CI], 58.9%-90.4%) with a false-positive rate of 17.9% (95% CI, 15.0%- 21.1%), whereas the sensitivity of logistic regression coefficients was 93.5% (95% CI, 78.6%-99.2%) with a false-positive rate of 34.6% (95% CI, 30.9%-38.4%). There was significant difference in screening efficiency for Down syndrome detection between the two methods (exact McNemar X
^{2}, P < .001 ). Conclusions-With a slight reduction in the Down syndrome detection rate, the use of the likelihood ratio approach was associated with a significantly lower false-positive rate compared with the logistic regression approach.

Original language | English (US) |
---|---|

Pages (from-to) | 463-469 |

Number of pages | 7 |

Journal | Journal of Ultrasound in Medicine |

Volume | 30 |

Issue number | 4 |

State | Published - Apr 1 2011 |

Externally published | Yes |

### Fingerprint

### Keywords

- Down syndrome
- Genetic sonogram
- Likelihood ratios
- Logistic regression coefficients

### ASJC Scopus subject areas

- Radiology Nuclear Medicine and imaging
- Radiological and Ultrasound Technology

### Cite this

*Journal of Ultrasound in Medicine*,

*30*(4), 463-469.

**The genetic sonogram : Comparing the use of likelihood ratios versus logistic regression coefficients for down syndrome screening.** / Zhong, Yan; Longman, Ryan E; Bradshaw, Rachael; Odibo, Anthony O.

Research output: Contribution to journal › Article

*Journal of Ultrasound in Medicine*, vol. 30, no. 4, pp. 463-469.

}

TY - JOUR

T1 - The genetic sonogram

T2 - Comparing the use of likelihood ratios versus logistic regression coefficients for down syndrome screening

AU - Zhong, Yan

AU - Longman, Ryan E

AU - Bradshaw, Rachael

AU - Odibo, Anthony O.

PY - 2011/4/1

Y1 - 2011/4/1

N2 - Objectives-The purpose of this study was to compare the screening efficiency for Down syndrome using likelihood ratios versus logistic regression coefficients. Methods-We conducted a retrospective study of women at increased risk for Down syndrome referred for a second-trimester genetic sonogram. Likelihood ratios were calculated by multiplying the risk ratio from maternal serum screening by the likelihood ratios of sonographic markers. Logistic regression coefficients were calculated using a formula derived from β coefficients generated from a multivariable logistic regression model. The screening efficiency of both methods was tested in an independent population of patients. The McNemar test was used to compare the predictive ability of the two methods. Results-In the validation population, the use of likelihood ratios had an area under the receiver operator characteristic curve of 0.90 for Down syndrome detection, whereas the use of logistic regression coefficients had an area under the curve of 0.86. Adopting a risk cutoff point of 1/270, the sensitivity of likelihood ratios was 77.4% (95% confidence interval [CI], 58.9%-90.4%) with a false-positive rate of 17.9% (95% CI, 15.0%- 21.1%), whereas the sensitivity of logistic regression coefficients was 93.5% (95% CI, 78.6%-99.2%) with a false-positive rate of 34.6% (95% CI, 30.9%-38.4%). There was significant difference in screening efficiency for Down syndrome detection between the two methods (exact McNemar X 2, P < .001 ). Conclusions-With a slight reduction in the Down syndrome detection rate, the use of the likelihood ratio approach was associated with a significantly lower false-positive rate compared with the logistic regression approach.

AB - Objectives-The purpose of this study was to compare the screening efficiency for Down syndrome using likelihood ratios versus logistic regression coefficients. Methods-We conducted a retrospective study of women at increased risk for Down syndrome referred for a second-trimester genetic sonogram. Likelihood ratios were calculated by multiplying the risk ratio from maternal serum screening by the likelihood ratios of sonographic markers. Logistic regression coefficients were calculated using a formula derived from β coefficients generated from a multivariable logistic regression model. The screening efficiency of both methods was tested in an independent population of patients. The McNemar test was used to compare the predictive ability of the two methods. Results-In the validation population, the use of likelihood ratios had an area under the receiver operator characteristic curve of 0.90 for Down syndrome detection, whereas the use of logistic regression coefficients had an area under the curve of 0.86. Adopting a risk cutoff point of 1/270, the sensitivity of likelihood ratios was 77.4% (95% confidence interval [CI], 58.9%-90.4%) with a false-positive rate of 17.9% (95% CI, 15.0%- 21.1%), whereas the sensitivity of logistic regression coefficients was 93.5% (95% CI, 78.6%-99.2%) with a false-positive rate of 34.6% (95% CI, 30.9%-38.4%). There was significant difference in screening efficiency for Down syndrome detection between the two methods (exact McNemar X 2, P < .001 ). Conclusions-With a slight reduction in the Down syndrome detection rate, the use of the likelihood ratio approach was associated with a significantly lower false-positive rate compared with the logistic regression approach.

KW - Down syndrome

KW - Genetic sonogram

KW - Likelihood ratios

KW - Logistic regression coefficients

UR - http://www.scopus.com/inward/record.url?scp=79953309689&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79953309689&partnerID=8YFLogxK

M3 - Article

C2 - 21460145

AN - SCOPUS:79953309689

VL - 30

SP - 463

EP - 469

JO - Journal of Ultrasound in Medicine

JF - Journal of Ultrasound in Medicine

SN - 0278-4297

IS - 4

ER -