1. What is the role of reliability and validity in the screening process?
Screening validity is the ability to distinguish between those with disease and those without accurately. Screening validity can be measured mainly by Sensitivity and Specificity; specificity refers to the test's ability to identify those who do not have the disease correctly, and sensitivity refers to the test's ability to accurately identify those who have the disease (Boston University, n.d.).
Screening reliability is based on the assumption that reliable tests give consistent results with repeated tests (Boston University, n.d.). For example, if a patient's blood sample has a blood glucose level of 100 mg/dL, the same blood sample should read 100 mg/dL each time, even trying screening multiple times. However, "variability in the measurement can be the result of physiologic variation or the result of variables related to the method of testing" (Boston University, n.d., para.4). In other words, if the patient's blood glucose level changes, the reading changes, but that is the patient's variability and does not imply a low test accuracy.
The role of reliability and validity in the screening process
・Enables accurate diagnosis and treatment
If screening lacks reliability and validity, doctors' diagnosis lacks accuracy. If the doctor's diagnosis is wrong, there will be no proper treatment. If the screening misses an abnormality that should be treated, or if it detects an abnormality as normal (false negative), the patient will have a false sense of security and will miss the opportunity for treatment. Not only that, but false negatives can lead people to believe they are healthy and spread the infection to more people when they actually have the disease. Conversely, if the screen erroneously detects normal as abnormal (false positives), it can lead to unnecessary treatment or drug administration to the patient. Maintaining reliability and validity in the screening process enables accurate diagnosis and treatment.
・Encourages people to take screening regularly
In most cases, getting screened comes at a cost. Patients have to bear financial costs, time costs, and pain/discomfort. If screening lacks reliability and validity, people would no longer feel the need to incur these costs and get screened. Conversely, if the reliability and validity of screening are established, people will take screening believing that early detection and treatment of disease is possible.
2. How do these two concepts affect the process and outcome of screening tests?
The validity and accuracy of results are often affected by screening objectives, methods, and internal and external circumstances.
For example:
・Techniques and methods of health care workers who conduct screenings
・The physical state of the patient (e.g., hungry or not at the time of screening)
・How to store the sample collected from the patient (temperature, storage period, etc.)
・Techniques and methods of clinical laboratory technologists who examine samples
In other words, certain standards and efforts are necessary to improve the validity of screening sensitivity and specificity and maintain reliability. Thus, the concept of reliability and validity of screening encourages healthcare professionals to follow the procedures and steps of the screening process, and to encourage patients to follow their instructions.
Thank you for your instruction, professor. (513 words)
References
Boston University. (n.d.). Screening for disease. Retrieved from http://sphweb.bumc.bu.edu/otlt/MPH-Modules/EP/EP713_Screening/EP713_Screening_print.html
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