PubMed · 8597852
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
D R Benjamin. The pendulum.. https://doi.org/10.3109/15513819509027002
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The analytical result of a laboratory examination is a scientific fact and has no medical meaning as such. It must be interpreted to become a medical finding. To explain the very complex cognitive procedure of the interpretation a three-level model is used. In an environment of cost containment in health care systems the quality of medical laboratory findings is very important. Analytical results are monitored by quality control procedures. For measuring the performance of medical findings the concept of the 'validity' of a laboratory test is used. Validity means the 'degree of achieving the objective'. Accordingly, a valid laboratory finding is one which correctly answers the question which the physician at the sick-bed directs to the laboratory. Quantitative measures for the validity of interpretation can be developed by an analysis of the underlying classification processes. Characteristic indices describing the validity quantitatively in terms of conditional probabilities can be derived from decision tables. Examples of 'validity indices' are diagnostic (or prognostic) 'sensitivity' and 'specificity'. These indices are powerful tools for developing strategies for the clinical use of laboratory examinations in diagnosis, prognosis and therapy management. Moreover, validity indices are appropriate output quantities for the estimation of effectiveness and efficiency of a diagnostic or prognostic examination.
The formulation of analytical goals for the clinical laboratory should be based upon a wide perspective embracing multiple viewpoints. Mathematical consideration of analytical error is necessary but insufficient to address societal forces demanding increased effectiveness while also reducing costs. Appropriate goals also require the study of cognitive science, health policy research, and the measurement of subjective preferences and of predictive probability. Overall goals must focus on health outcomes that emphasize prevention or postponement of morbidity and the need for acute care. Care process variables that influence health outcomes must be identified. Process improvement through reduction in process variation can then improve health outcomes. Important process variables will be identified in the cognitive process as well as in the pre- and post-analytical phases of laboratory care. The impact of test characteristics upon the laboratory's contribution to health goals are exemplified by monitoring of oral anticoagulant, thyroxine, aminoglycoside and intensive insulin therapy plus identification of clinically occult diseases such as hypothyroidism and hemochromatosis.
Limits of maximum allowable analytical imprecision have been defined on the basis of normal range (Tonks), composite biological variation (Cotlove), intraindividual biological variation (Aspen Conference, College of American Pathologists), medical significance (Barnett, Skendzel), and a combination of medical significance and biological variation (Fritsche. Klee). Because error limits based on medical significance are less stringent than those based on biological variation, performance goals based on medical significance are more likely to be attained by laboratories than those defined by biological variation. Most clinical scientists realize that the goal to limit the analytical C.V. to one-half or less of the biological C.V. is arbitrary, and for the large majority of laboratory tests of no benefit to the patient, for the major component of total variation is not the analytical imprecision, but the intraindividual variation itself. Furthermore, the purpose of laboratory testing is to help physicians confirm or exclude potential diagnoses and monitoring therapy rather than detecting small deviations from normal values. Small changes in test values are quite often uninterpretable or lead to costly albeit fruitless investigations. In view of diminishing resources for health care we must establish the accuracy and precision required for each test. While improving the accuracy of some tests would be desirable, for most of them further improvement would be irrelevant to patient care because few tests are pathognomonic by themselves and quite often diagnosis is not made on the basis of a single laboratory result. If more accuracy is desirable, it must also be affordable and benefits should outweigh costs.