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Diagnostic Accuracy of Lymphoscintigraphy for Lymphedema and Analysis of False-Negative Tests.

ABSTRACT: Lymphedema is the chronic enlargement of tissue due to inadequate lymphatic function. Diagnosis is made by history and physical examination and confirmed with lymphoscintigraphy. The purpose of this study was to assess the accuracy of lymphoscintigraphy for the diagnosis of lymphedema and to determine characteristics of patients with false-negative tests.Individuals referred to our lymphedema program with "lymphedema" between 2009 and 2016 were analyzed. Subjects were assessed by history, physical examination, and lymphoscintigraphy. Patient age at presentation, duration of lymphedema, location of disease, gender, previous infections, and lymphedema type were analyzed.The study included 227 patients (454 limbs); lymphedema was diagnosed clinically in 169 subjects and confirmed by lymphoscintigraphy in 162 (117 primary, 45 secondary; 96% sensitivity). Fifty-eight patients were thought to have a condition other than lymphedema, and all had negative lymphoscintigrams (100% specificity). A subgroup analysis of the 7 individuals with lymphedema clinically, but normal lymphoscintigrams, showed that all had primary lymphedema; duration of disease and infection history were not different between true-positive and false-negative lymphoscintigram results (P = 0.5). Two patients with a false-negative test underwent repeat lymphoscintigraphy, which then showed lymphatic dysfunction consistent with lymphedema.Lymphoscintigraphy is very sensitive and specific for lymphedema. All patients with false-negative studies had primary lymphedema. A patient with a high clinical suspicion of lymphedema and a normal lymphoscintigram should be treated conservatively for the disease and undergo repeat lymphoscintigraphy.

SUBMITTER: Hassanein AH

PROVIDER: S-EPMC5548565 | biostudies-other | 2017 Jul

REPOSITORIES: biostudies-other

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Project description:Overall accuracy measures of medical tests are often used with unclear interpretations. To develop methods of calculating the overall accuracy of medical tests in the patient population. Algebraic equations based on Bayes' theorem. A new approach is proposed for calculating overall accuracy in the patient population. Examples and applications using published data are presented. The overall accuracy is the proportion of the correct test results. We introduce a clear distinction between the overall accuracy measures of medical tests that are aimed at the detection of a disease in a screening of populations for public health purposes in the general population and the overall accuracy measures of tests aimed at determining a diagnosis in individuals in a clinical setting. We show that the overall detection accuracy measure is obtained in a specific study that explores test accuracy among persons with known diagnoses and may be useful for public health screening tests. It is different from the overall diagnostic accuracy that could be calculated in the clinical setting for the evaluation of medical tests aimed at determining the individual patients' diagnoses. We show that the overall detection accuracy is constant and is not affected by the prevalence of the disease. In contrast, the overall diagnostic accuracy changes and is dependent on the prevalence. Moreover, it ranges according to the ratio between the sensitivity and specificity. Thus, when the sensitivity is greater than the specificity, the overall diagnostic accuracy increases with increasing prevalence, and vice versa, that is, when the sensitivity is lower than the specificity, the overall diagnostic accuracy decreases with increasing prevalence so that another test might be more useful for diagnostic procedures. Our paper suggests a new and more appropriate methodology for estimating the overall diagnostic accuracy of any medical test. This may be important for helping clinicians avoid errors.

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Diagnostic Accuracy of Lymphoscintigraphy for Lymphedema and Analysis of False-Negative Tests.

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