The evaluation of biological markers for quantitative risk assessment was discussed. The concept of validity included measurement validity, internal study validity, and external validity. Measurement validity can be defined as the extent to which a measurement means exactly what it claims to measure. Measurement validity can also be characterized as the degree to which a biomarker has content validity, construct validity, and criterion validity. Internal validity was discussed. Internal validity refers to the degree to which inferences drawn from a sample are warranted when the study method, representativeness of the study sample, and the characteristics of the population are considered. Internal validity depends on the ability to control biases, misclassification, and to choose the correct mathematical model for treating the data. External validity was discussed. External validity is the extent to which a study can produce unbiased inferences about the target population and involves the appropriateness of extrapolating between populations or species, from high to low doses, or between different organs in a given species. The concepts of measurement, internal, and external validity were illustrated by applying them to risk assessments of the carcinogenicity of ethylene-dibromide (106934) using bromine (7726956) release as a marker of exposure and the genotoxicity and carcinogenicity of ethylene-oxide (75218) using hemoglobin alkylation as a biomarker. Hemoglobin alkylation was found to be a valid marker for ethylene-oxide exposure. Bromine release was of little value for assessing the risk of ethylene-dibromide. The bromine release data suggested that a threshold exists whereas other data indicated that ethylene-dibromide alkylated macromolecules and caused mutations at doses below the supposed threshold. The authors conclude that before biological markers can be used in risk assessments they must be shown to be reliable. Failure to do so can result in erroneous conclusions.
Links with this icon indicate that you are leaving the CDC website.
The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website.
Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
You will be subject to the destination website's privacy policy when you follow the link.
CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website.
For more information on CDC's web notification policies, see Website Disclaimers.
CDC.gov Privacy Settings
We take your privacy seriously. You can review and change the way we collect information below.
These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. They help us to know which pages are the most and least popular and see how visitors move around the site. All information these cookies collect is aggregated and therefore anonymous. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance.
Cookies used to make website functionality more relevant to you. These cookies perform functions like remembering presentation options or choices and, in some cases, delivery of web content that based on self-identified area of interests.
Cookies used to track the effectiveness of CDC public health campaigns through clickthrough data.
Cookies used to enable you to share pages and content that you find interesting on CDC.gov through third party social networking and other websites. These cookies may also be used for advertising purposes by these third parties.
Thank you for taking the time to confirm your preferences. If you need to go back and make any changes, you can always do so by going to our Privacy Policy page.