Reference Intervals (RIs), Normal Values, Health Status and Clinical Decision Limits (CDLs), the Theory and the Practice Volume 2 - Issue 2

Ibrahim A Ali*

• Department of Physiology, Faculty of Medicine, The National Ribat University, Khartoum, Sudan

Received:June 25, 2020   Published: July 06, 2020

Corresponding author:Ibrahim Abdelrhim Ali, Assistant Professor of Medical Physiology, Department of Physiology, Faculty of Medicine, The National Ribat University, Khartoum, Sudan

DOI: 10.32474/JCCM.2020.02.000133

 

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Abstract

There was a clear distinction between healthy reference values measured in healthy populations or individuals and patient reference values measured in patients having various diseases. It is now commonly accepted that reference values describe fluctuations observed in healthy populations or individuals, which makes the definition of health or characterization of health status a critical step.
From 1987 to 1991, the International Federation of Clinical Chemistry (IFCC) published a series of 6 papers, in which it was recommended that each laboratory follow defined procedures to produce its own reference values. Although there were very important developments and implementations between the 1990s and 2008; the C28- A3 guideline, published in 2008 by Clinical and Laboratory Standards Institute (CLSI) and IFCC constituted the most significant step in the development of RIs and is still in current use
From its inception, and according to IFCC definition, reference values are measured in a well-characterized population of individuals selected according to predefined criteria such as age, sex, nutritional status, and diet. In addition, it is presumed that reference individuals are healthy, which raises the question of the definition of health. There is no accepted consensus on the definition of health.
The RIs are descriptive of a specific population and are derived from a reference distribution (usually 95% interval), whereas CDLs are thresholds above or below which a specific medical decision is recommended and are derived from Receiver Operating Characteristic (ROC) curves and predictive values. CDLs are based on the diagnostic question and are obtained from specific clinical studies to define the probability of the presence of a certain disease or a different outcome. These limits lead to the decision that individuals with values above or below the decision limit should be treated differently. CDLs are defined by consensus and vary among different populations. It is important that RIs are not confused with CDLs.
To avoid confusion, the C28-A3 recommended reporting decision limits or RIs but not both, with a clear indication of which has been used.

Keywords: Reference Intervals (RIs); Normal Values; Health Status And Clinical Decision Limits (CDLs)

Abstract| Introduction| Reference intervals (RIs), health status and clinical decision limits (CDLs)| References|