A note on ascertainment probability in the Allen/Hrubec twin model

Area of Science:

• Biostatistics
• Genetic Epidemiology
• Twin Studies

Background:

• The Allen and Hrubec model introduced secondary ascertainment rates for twin concordance.
• This rate considers partial ascertainment of secondary cases in twin studies.

Purpose of the Study:

• To evaluate the utility of the secondary ascertainment rate in twin concordance models.
• To determine the conditions under which the proband method and Allen/Hrubec model are valid.

Main Methods:

• Critically analyzed the concept of secondary ascertainment rate.
• Assessed the requirements for including twin pairs in genetic analyses.
• Examined the conditions for the validity of the proband method and Allen/Hrubec model.

Main Results:

• The secondary ascertainment rate has limited interest as only complete twin pair data is valuable for genetic analysis.
• The validity of the proband method and Allen/Hrubec model hinges on equivalent ascertainment in concordant and discordant pairs.
• Established a relationship between cotwin ascertainment probability and population ascertainment probability when conditions are met.

Conclusions:

• The secondary ascertainment rate is of limited practical value in genetic analyses of twin data.
• Ensuring equivalent ascertainment across pair types is crucial for valid twin study models.
• The study clarifies the relationship between ascertainment probabilities in twin populations.