Table of Contents

## What is reference interval in clinical chemistry?

In the clinical laboratory, reference interval (RI) is the interval between, and including, two reference limits. It is the most widely used medical decision-making tool that separates healthy from diseased individuals.

**How do you determine the reference intervals in a clinical laboratory?**

The lower reference limit would be the third number from the beginning (top) of the sorted list and the upper reference limit would be the third number from the (end) bottom. The reference range would be the central 95% of the data, which falls between the 3rd and 117th values.

### What is reference interval in laboratory?

Reference intervals are the most common decision support tool used for interpretation of numerical pathology reports. As laboratory results may be interpreted by comparison with these intervals, the quality of the reference intervals can play as large a role in result interpretation as the quality of the result itself.

**What is reference interval in statistics?**

A reference interval (sometimes called a reference range or normal range) describes the range of values of a measured quantity in healthy individuals. Reference limits. A reference limit defines a value where a given proportion of reference values are less than or equal to.

## What is the purpose of a reference range?

Reference ranges help describe what is typical for a particular group of people based on age, sex, and other characteristics. In the context of your personal information, you and your provider can use reference ranges as a guide to what your results mean and to help make decisions about managing your health.

**How are reference intervals calculated?**

The reference interval is calculated using 3 different methods: (a) using the Normal distribution (Bland, 2000; CLSI 2008), (b) using a non-parametrical percentile method, and (c) optionally a “robust method” as described in the CLSI Guidelines C28-A3. 90% Confidence Intervals are given for the reference limits.

### How do you find the reference interval?

Confidence interval of limit The 90% confidence interval of a standard reference range limit as estimated assuming a normal distribution can be calculated by: Lower limit of the confidence interval = percentile limit – 2.81 × SD⁄√n.

**How would you define reference intervals to rule in healthy individuals for clinical trials?**

Reference intervals are commonly used as a decision making tool [1]. The majority of reference intervals refer to the central 95% of the reference population, commonly defined as the mean±2 standard deviations (SDs) or 0.025 and 0.975 percentiles from a population free from disease [2], [3].

## Why are reference ranges different?

Why Labs Have Different Reference Ranges Because there is no universal reference range for most lab tests, ranges will vary from lab to lab. This means that it is possible to get a normal result from one lab and an abnormal result for the same test from another lab, and vice versa.

**How are reference intervals derived?**

Derivation of reference intervals. RIs were derived by the parametric method after normalizing data using modified Box-Cox power transformation formula [8] and non-parametric method for both sexes and age groups.

### Why do reference ranges change?

A reference range can vary between different laboratories when a collection of people who are considered ‘normal’ are used to establish a reference range for a given blood test. Complex mathematics are applied to allow for a natural variation within this chosen collection of people and therefore the reference range.

**What is a reference interval?**

Reference intervals are essential for clinical laboratory test interpretation and patient care. Methods for estimating them are expensive, difficult to perform, often inaccurate, and nonreproducible.

## What is the relationship between laboratory methods and reference intervals?

The method used in the laboratory to produce patient results is an important factor in setting reference intervals. If data are obtained from the literature or other laboratories the relationship between the methods must be understood. The key factors are the accuracy base and analytical specificity.

**How many samples should be used to validate a reference interval?**

The CLSI guideline C28-A3 ( 12) allows for subjective validation of a reference interval by laboratory assessment of population demographics and preanalytical and analytical parameters. A more formal validation recommends using 20 (60 for a more robust analysis) samples from local healthy individuals.

### How do you determine health-associated reference intervals?

Health-associated reference intervals including shared (i.e., common or harmonized) reference intervals can be determined by formal (direct) studies using a local population and specified preanalytical conditions or by (indirect) data mining drawn from a local population in which specified preanalytical conditions are used.