Influence of Index of Individuality on False Positives in Repeated Sampling from Healthy Individuals
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Per Hyltoft Petersen
Abstract
The index of individuality is defined as the ratio of the within-subject biological variation to the between-subject variation, i.e., the variation between the biological set-points. It has been disputed whether the index of individuality has influence on the usefulness of conventional population-based reference intervals. In this investigation we found that, as long as only a single sample is taken, for a certain change in an individual's set-point, the index of individuality has no influence on the usefulness of reference intervals. When two or more samples are taken into account, however, the outcome of the measurement is highly dependent on the index of individuality. For a low index, repeat measurement has only limited effect on the fraction of false-positive results, as the next result will be close to the first, but, when the index is high, the fraction of false-positive results will be reduced considerably through repeating the test. Moreover, the distribution of biological set-points for which the fraction of false-positive results originate is described and the influence of analytical imprecision is discussed. The calculations are performed for values of the index of individuality from 0 to 2.0 for the traditional 95% reference interval based on x̄ ± 2*stotal (stotal = total biological variation), and also for a decision limit (cut-off point) x̄ ± 3*stotal. The numbers are, of course, different, but the effects of the index of individuality are the same, independent of the chosen cut-off point.
This concept is related to the clinical classification (diagnosis, prognosis, screening) and the difference from different principles of monitoring is discussed. Further, five examples are evaluated and aspects of index of individuality in relation to false-positive results are discussed.
Copyright (c) 2001 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- Special Issues of the Journal
- Clinical Biological and Genetic Heterogeneity of the Inborn Errors of Pulmonary Surfactant Metabolism
- The Effects of Impaired Trace Element Status on Polymorphonuclear Leukocyte Activation in the Development of Vascular Complications in Type 2 Diabetes Mellitus
- Free and Complexed Prostate-Specific Antigen (PSA) in the Early Detection of Prostate Cancer
- Heterogeneity of DNA Methylation Status Analyzed by Bisulfite-PCR-SSCP and Correlation with Clinico-Pathological Characteristics in Colorectal Cancer
- Serum Amyloid A Protein (SAA) in Colorectal Carcinoma
- Metal Exposure from Amalgam Alters the Distribution of Trace Elements in Blood Cells and Plasma
- Diabetic Cataract and the Total Antioxidant Status in Aqueous Humor
- Candidate Gene Polymorphism in Cardiovascular Disease: A Comparative Study of Frequencies between a French and an Italian Population
- Reference Values for Plasma Dipeptidyl Peptidase IV Activity and Their Association with Other Laboratory Parameters
- Influence of Index of Individuality on False Positives in Repeated Sampling from Healthy Individuals
- Regional Reference Values for some Quantities Measured with the ADVIA Centaur Analyser. A Model of Co-operation between the In Vitro Diagnostic Industry and Clinical Laboratories
- Tissue Polypeptide-Specific Antigen (TPS) Concentrations in Cerebrospinal Fluid in Patients with Breast Cancer Metastases in the Central Nervous System
- The Measurement of Anti-Hepatitis C Virus Antibody in Sera Using a New Generation Immunoassay
- Quality Specifications for Cardiac Troponin Assays
- IFCC News January 2001
