Table 3.

Evaluating the validity of genetic tests

Term	Definition	Complications in molecular tests	Calculation
Analytical sensitivity	Refers to the proportion of assays with the genotype that have a positive test result (false-negative rate of the assay)	Allele drop out; preferential amplification; mosaicism	True positives/(true positives + false negatives)
Analytical specificity	Refers to the proportion of assays without the genotype that have a negative test result (false-positive rate of the assay)		True negatives/(true negatives + false positives)
Clinical sensitivity	Refers to the proportion of people with a disease who have a positive test result (false-negative rate of diagnosis)	Variable penetrance; variable expressivity	True positives/(true positives + false negatives)
Clinical specificity	Refers to the proportion of people without a disease who have a negative test result (false-positive rate of diagnosis)		True negatives/(true negatives + false positives)
Positive predictive value (PPV)	Refers to the likelihood that a patient has the disease given that the test result is positive		True positives/(true positives + false positives)
Negative predictive value (NPV)	Refers to the likelihood that a patient does not have the disease given that the test result is negative		True negatives/(true negatives + false negatives)
Clinical utility	Refers to the value of the test for determining treatment, patient management and family planning	Depends on health-care system and environment	Subjectively determined on the basis of reports supporting use and economic benefits
Personal utility	Refers to the value of the test for personal and family choices	Depends on personal vantage	Subjectively determined from an individual’s perspective