Clinical examination and laboratory investigation as diagnostic tests.

Abstract

The main tools that a physician uses for medical diagnosis are clinical history and clinical examination. Hampton et al. in 1970 showed in 80 English outpatients that clinical history was responsible by 82.5% of medical diagnosis, clinical examination for more 8.75%, and other tests for more 8.75%. Study done in HCFMUSP showed that clinical history was responsible for 40.4% of medical diagnosis, clinical examination for more 29.4% e other tests for more 29.5%. A laboratory test or image procedure always brings information about sensitivity and specificity of the method. However, it not common to teach the sensitivity or specificity of information obtained at clinical history or clinical examination. Results from a diagnostic test compared to a gold-standard permit the contruction of a 2 x 2 table with four possible interpretations of the results: (1) true positive, when test is positive in the presence of disease; (2) false-positive when it is positive in the absence of disease; (3) true negative when test is negative in the absence of disease; false-negative, when test is negative in the presence of disease. Based on these possibilities it is possible to calculate sensititivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios. Interpretation of the information collected as part of clinical history or examination as diagnostic tests refine their role in the clinical investigation and final diagnosis. Health costs are finite and limited to the public budget, and even in a tertiary care facility there are restrictions to the execution of these tests caused by an imbalance among demand and the capacity to perform the tests. The use of this type of tool permit the use of the tests in patients with the greatest necessity of them, and the main consequence is a better management of the health system as a whole.