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Introduction to Clinical Chemistry

An introduction to clinical chemistry and the measurement of chemical substances in biological specimens.

4 min read Clinical Chemistry #electrolytes #albumin #concentration #mass-concentration #cholesterol
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Learning Objectives

By the end of this resource you should be able to:

- Define clinical chemistry.
- Identify common analytes measured by clinical chemistry laboratories.
- Recognize common chemistry specimen types.
- Explain how analytical and pre-analytical factors affect chemistry results.

Introduction to Clinical Chemistry

Overview

Clinical chemistry, also called clinical biochemistry, is the laboratory discipline concerned with measuring chemical and biochemical substances in biological specimens.

Its measurements can contribute to assessment of metabolic processes, organ function, disease states, treatment response, and physiological status.

Common analytes

Depending on the laboratory, clinical chemistry may include measurement of:

  • Glucose
  • Electrolytes
  • Urea
  • Creatinine
  • Proteins
  • Albumin
  • Bilirubin
  • Enzymes
  • Lipids
  • Minerals
  • Selected hormones and biomarkers

LabGoTo's dedicated calculator and reference-range sections should be used for specific calculations and reference information rather than treating this overview as a substitute for those resources.

Common specimens

Serum and plasma are widely used for chemistry examinations. The correct specimen depends on the analyte, analytical method, collection system, and laboratory procedure.

Some examinations may require other specimen types, including urine or body fluids.

Pre-analytical considerations

Clinical chemistry results can be influenced by:

  • Patient preparation
  • Collection technique
  • Tube or additive selection
  • Time between collection and processing
  • Centrifugation
  • Temperature
  • Hemolysis
  • Lipemia
  • Icterus
  • Contamination
  • Storage conditions

The effect of each factor is analyte- and method-dependent.

Analytical measurement

A chemistry analyzer measures a defined measurand using a particular analytical principle. Methods can involve photometric, potentiometric, immunochemical, enzymatic, electrochemical, or other measurement approaches.

A laboratory must establish that its examination procedures are appropriate for their intended use and maintain the conditions required for reliable performance.

Calibration and quality control

Calibration and quality control are related but distinct activities.

Calibration establishes or adjusts the measurement relationship used by an analytical system according to the applicable method.

Quality control monitors analytical performance using defined control procedures and materials.

A laboratory should investigate unacceptable QC performance according to its documented procedure.

Result interpretation

A measured concentration does not have a universal meaning independent of context. Interpretation may depend on:

  • Patient characteristics
  • Specimen type
  • Analytical method
  • Reference interval or decision limit
  • Timing
  • Pre-analytical conditions
  • Other laboratory findings
  • Clinical information

Key points

  • Clinical chemistry measures chemical and biochemical constituents of biological specimens.
  • Serum and plasma are common chemistry specimens.
  • Pre-analytical conditions can significantly affect results.
  • Analytical methods and instruments are method-specific.
  • Calibration and QC serve different purposes.
  • Specific calculations and reference ranges should be handled using validated dedicated resources.

References

  • NCBI. MeSH: Chemistry, Clinical.
  • World Health Organization. Laboratory Quality Management System: Handbook.
  • ISO 15189:2022. Medical laboratories — Requirements for quality and competence.