Likelihood Ratio of Down Syndrome vs Normal Karyotype with use of Humerus Length (MoM)
Expected Median Humerus Length = -6.30134 + BPD x 0.77612
Humerus Length MoM = Measured Humerus Length/Expected Median Value of Humerus
Risk = Maternal Age Risk x Likelihood Ratio eg 1/270 x 1.49 = 1/181
*Risk may be calculated from multiple sonographic markers by multiplying the likelihood ratios by the maternal age risk eg Maternal Age Risk x Humeral MoM, Nuchal MoM, Hypoplastic 5th Digit MoM, etc
Adapted from:Bahado-Singh R, Deren O, Oz U, Tan A, Hunter D, Copel J, Mahoney MJ. An alternative for women initially declining genetic amniocentesis: Individual Down syndrome odds on the basis of maternal age and multiple ultrasonographic markers. Am J Obstet Gynecol 179:514-9, 1998.