In other words, specificity is the proportion of the population without the target disorder who test negative for the disorder i.e D/(B+D). Specificity is the ability of a test to identify patients that do not have the disorder in question. So, if the test is negative, the examiner can be confident that the patient does not have impingement. įor example, the Neers Test has been reported to have a sensitivity rating of 0.93 for detecting subacromial impingement. ' SnNout' is an acronym that can be used to remember that a highly sensitive test and a negative result is good for ruling out the disorder in question. Tests that are highly sensitive are most useful for ruling out a disorder, as people who test negative are more likely not to have the target disorder. In other words, it represents the proportion of a population with the target disorder that has a positive result with the diagnostic test i.e A/(A+C). Sensitivity is defined as the ability of a test to identify patients with a particular disorder. It reflects the proportion of tests that are correct however, because it does not distinguish false test results, it is considered of limited value. The overall accuracy of a test is defined as the number of correct results divided by the total number of tests conducted i.e. The results of the diagnostic test should be unknown to examiners The results of the reference standard should be unknown to examinersĪpplied consistently to all study participants Test description in terms of procedures, performance and interpretation of results should be clear Intended purpose of test should be clearly defined Population should be representative of patients on whom test is used Fritz and Wainner have summarised these issues in a tabular form which is presented below. Other factors may also contribute to study bias such as the study population, the diagnostic test, the reference standard and these should be carefully considered when evaluating the results of a study. Study bias refers to the successibity of study results to deviation from the truth in a consistent manner. The optimal study design for diagnostic studies is suggested to be the prospective cohort study in this design, the prospective blind comparison of the test(s) and the reference standard in a sample of patients relevant to clinical practice can reduce possible study bias. This is accomplished by comparing the performance of the test in question with a reference or 'gold' standard in a 2x2 contigency table. Diagnostic accuracy ĭetermining the diagnostic accuracy through the estimation of sensitivity and specificity of a test is the first step in the evaluation of a diagnostic test. Some data may be used to focus the examination on a specific part of the body, other to identify a specific pathology and some to select an appropriate intervention.

The diagnostic process begins with aquiring relevant data from the history and physical examination. Through the physiotherpy assessment, clinicians gather data to evaluate and form clinical judgements. Physical therapists use the diagnosis of specific conditions to guide their treatment options. Knowing the diagnostic accuracy of special tests is important in obtaining an accurate diagnosis, and in turn maximizing treatment outcomes. Diagnostic accuracy statistics are often used to describe the effectiveness of special tests in identifying specific disorders. The purpose of this page is to provide users of Physiopedia a quick reference to commonly used diagnostic statistics in physical therapy practice and issues around evaluation of these statistics in clinical research. 3.7 Statistical Significance and Confidence Intervals.2 Diagnosis in Physical Therapy Practice.

Diagnostics test