Model Risk Calculations

Model risk calculations

Model risk calculations have been prepared for cystic fibrosis (CF) andSMN1-related spinal muscular atrophy (SMA) by a small team convened by the ACGS Quality Subcommittee.

These model risk calculations consist of a subset of scenarios commonly encountered in diagnostic genetics laboratories for CF and SMA carrier testing. For each scenario, the residual carrier risk is estimated following a test result where no mutation is identified.

The calculations are provided as a guide for laboratories for information and training purposes. The assumptions that the calculations are based on are outlined at the start of each document, for example regarding carrier frequency and test sensitivity. Laboratories/users should adjust these figures as appropriate.

Many alternative approaches are possible for risk calculations of this type. In general. we have adopted a Bayesian strategy, but even then many variations are possible. Therefore, for each calculation, at least two related approaches are given with accompanying explanations.

We aim to add further model calculations in the future, including some scenarios for Duchenne muscular dystrophy testing.

We welcome comments and suggestions regarding possible alternative approaches or answers for the scenarios included here, and also suggestions for further examples that may be helpful. Please contact Carl Fratter if you have any comments or suggestions (

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