Patent ID: 8071283

Claim:
A method of determining a likelihood of a fetus carried by a pregnant mother having a chromosomal abnormality using a first biological parameter and a second biological parameter, both of which parameters are suitable for screening said fetus for said chromosomal abnormality, the method comprising: receiving first data from a first stage of pregnancy of said mother, said first data comprising data representing a first value of said first biological parameter which is PAPP-A, and data representing a first value of said second biological parameter, said second biological parameter comprising one of total hCG, Inhibin-A, AFP, and uE 3 ; receiving second data from a second, later stage of said pregnancy, said second data comprising data representing a second value of said first biological parameter and data representing a second value of said second biological parameter; wherein said first biological parameter is a marker for said chromosomal abnormality at the first stage of pregnancy and has substantially no value as a marker during the second stage of pregnancy, and wherein said second biological parameter is a marker for said chromosomal abnormality at said second stage of pregnancy and has substantially no value as a marker during the first stage of pregnancy, determining, using a computer, a multiple of median value for each of said values in said first and second data by dividing each of said values in said first and second data by a corresponding predicted median value; forming, using a computer, a feature vector y using said multiple of median values; determining a probability of an unaffected pregnancy given feature vector y; determining a probability of an affected pregnancy given feature vector y, and determining likelihood ratio data from said first and second data by calculating, using a computer, a ratio of said probability of an unaffected pregnancy to said probability of an affected pregnancy, said likelihood ratio data representing the likelihood of said fetus having a chromosomal abnormality.