Posterior probability
Final risk assessment after combining screening test results with maternal age and other factors in prenatal screening.
Full Definition
Posterior probability represents the final calculated risk for a specific condition after integrating screening test results with prior probability factors such as maternal age, gestational age, and other demographic variables. In prenatal screening, this provides the most accurate risk assessment by combining multiple sources of information rather than relying on individual test components alone. The posterior probability is typically expressed as a ratio (e.g., 1 in 250) and determines whether results fall above or below established screening cutoffs that would warrant offering diagnostic testing.
Usage
Usage note: Do not hyphenate. Distinguish from 'prior probability' which refers to age-related risk before testing.
In Context
- "The posterior probability for trisomy 21 was calculated as 1 in 180, exceeding the screening cutoff." — Screening test report
- "Posterior probability calculations incorporate maternal age-related risk with biochemical and ultrasound findings." — Laboratory methodology