Diagnostic Tests are Imperfect!!

Posted: February 22nd, 2010 | Filed under: Diagnostic Test | Tags: Diagnositc Tests, Gold Standard, Heart Conditions, Heart Disease, Heart Health, Investigation, Risk Factors |

Did you know that most of the diagnostic tests are often taken for granted by most of physicians and patients?And most of the Diagnostic information is imperfect!!

When any test or an diagnostic evaluation is ordered by the physician,it is most often taken as a true representation of what is really going on with the patient,when in reality it is an error.These tests may not reflect on truly what is going on with the patient.When any test is performed on the patient,two important concerns are safety and efficacy.The other important criteria is cost of the investigation.In the current era of rising costs,combing the two factors is critical for effective patient management.

The efficacy of a diagnostic test should be measured in terms of the test’s safety, its technical quality, its accuracy, its therapeutic impact, and its impact on the health of the patient (Fineberg et al. 1977).

The second stage of an efficacy assessment is to define the test’s diagnostic accuracy. In this regard, three commonly used expressions are true-positive rate, truenegative rate, and accuracy. The true-positive rate, or sensitivity, is a measure of the test’s ability to detect disease correctly when it is present. The true-negative rate, or specificity, measures the test’s ability to exclude disease in those patients who do not have it. Accuracy is the proportion of test results that are correct (true-positive results plus truenegative results divided by the total number of test results) when the test is used in a specified population. Thus, it is a reflection of both the sensitivity and the specificity of the test.To call a test result a true positive or a true negative, one must determine the true state of the patient. This is usually accomplished by doing another test, called the “gold standard,” which is considered sufficiently reliable to reveal the true state of the patient, and either confirm or refute the study test result. For example, coronary angiography has been used to verify the presence of coronary artery disease in patients participating in an efficacy study of the stress electrocardiogram. For an ideal test, there should be little disagreement between its result and the result of the “gold standard”: the test should have both high sensitivity and high specificity.

Although quantitative measures of test performance are important, a study of efficacy should not focus solely on its technical aspects (that is, on the machine). Rather, an assessment should include data on diagnostic impact and on therapeutic impact, including outcomes that are relevant to the patient. These are the third and fourth levels of an efficacy assessment.

The following questions needs to be asked by the patient to their health care provider before any diagnostic tests are performed on them:

1.Does the result of the technique change the diagnosis?

2.Does the technique add clinically significant information?

3.Is the diagnostic impact one that changes my management?

Do you have any experience with diagnostic tests?Share your experience !!