Exam (elaborations) Diagnostic research3190

It is a study that aims to quantify the accuracy of a test’s added contribution beyond the test results readily available to the physician or researcher in determining the presence or absence of a particular disease or to predict the two distinct categories of patients such as poor health or good health [1–7]. This type of study is very important for efficiently identifying and offering the appropriate medical management to the right patient [8–10]. Research design is one of the important factors that will define the success of diagnostic research, and one of the necessary considerations for any research design is to conduct proper sample size planning. Before calculating the required sample size, a researcher will need to first understand the overall concept, the underpinning assumptions, and all the measurable parameters for a diagnostic test. Figure 1 illustrates a common scenario for diagnostic research. In this example, the researcher aims to determine the accuracy of a particular screening test to determine the serum level of a particular biochemical marker for detecting colorectal cancer in a patient. The outcome of a diagnostic test must be objectively evaluated against a definitive measurement provided by a gold standard test such as in this case from a biopsy test. The True Positive (TP) cases are referring to those cases that actually have a positive diagnosis from among a group of positive cases detected by the test, whereas the True Negative (TN) cases are referring to those cases that actually do not have a positive diagnosis from among a group of negative cases detected by the test. This means that the sensitivity of a diagnostic or screening test is an assessment of how well it is able to detect the True Positive (TP) cases (e.g., patients with colorectal cancer) as compared to that of the gold standard technique (i.e., performing a biopsy from the organ itself); whereas, the specificity of a diagnostic or screening test is an assessment of how well it is able to detect the True Negative (TN) cases (e.g., patients without colorectal cancer) as compared to that of the gold standard technique (i.e., performing a biopsy from the organ itself). In other Diagnostics 2023, 13, 1390. Diagnostics 2023, 13, 1390 2 of 12 words, a diagnostic or screening test with a perfect score in having both the sensitivity and specificity values of 100%, respectively, can only be achieved when the False Positive (FP) and False Negative (FN) are both zero. Diagnostics 2023, 13, x FOR PEER REVIEW 2 of 13 the True Negative (TN) cases (e.g., patients without colorectal cancer) as compared to that of the gold standard technique (i.e., performing a biopsy from the organ itself). In other words, a diagnostic or screening test with a perfect score in having both the sensitivity and specificity values of 100%, respectively, can only be achieved when the False Positive (FP) and False Negative (FN) are both zero. Figure 1. Four possible scenarios in diagnostic research. Based on the above formula provided, the sensitivity and specificity of the test are calculated to be 87.8% and 83.3%, respectively. The Positive Predicted Value (PPV) is the proportion of people with a positive test result who actually have the disease and Negative Predicted Value (NPV) is the proportion of those with a negative result who do not have the disease. In this example, the values of PPV and NPV are then calculated to be 90.9% and 78.1%, respectively. Overall, the test has good sensitivity and specificity. Ideally, most researchers will always aim to achieve a perfect accuracy, which is a performance as good as the gold standard. However, this can rarely be achieved since a particular screening test that has been invented or developed will usually be far cheaper, offer a faster method of detection, and be more convenient and user-friendly in its procedures. Thus, most researchers will usually afford some allowances for its accuracy that are attributable to chance or random error [8–10]. Normally, there are three possible conclusions that can be drawn from diagnostic research. First, the test is both sensitive and specific and thus suitable for use as a diagnostic test or marker [1–5]. Second, the test can only be suitable for use as a screening tool since the test or marker is high in either its sensitivity or specificity (b