- 1.Important characteristics of diseases that are appropriate for screening include:
The disease should be important in the screened population.
The disease process should have a preclinical phase.
Treating the disease process at an early stage should provide benefit.
Reliability refers to the ability of a test to provide repeatable results.
Validity refers to the ability of a test to detect true disease, as defined by a gold standard.
- 4.Two important measures of validity are sensitivity and specificity:
Sensitivity is the probability of testing positive given the presence of disease.
Specificity is the probability of testing negative given the absence of disease.
- 5.The predictive values of a test are defined as:
Positive predictive value is the probability of true disease given a positive test.
Negative predictive value is the probability of no true disease given a negative test.
Disease prevalence is required for calculating the predictive values of a test.
High test specificity is needed to reduce false positives when screening for a rare disease.
ROC curves present sensitivity and specificity characteristics for all possible cutoff values of a continuous screening test.
- 9.Four potential biases in screening studies that may lead to spurious associations of a screening program with health outcomes are
Lead time bias
Length bias sampling
The association of a factor with disease must be extraordinarily strong to qualify that factor as a potentially useful screening test.