Types of Chromatography in Diagnostics
Laboratory practice utilizes a spectrum of chromatographic approaches, including:
- Gas-liquid chromatography (GLC) — the primary tool for detecting volatile compounds.
- High-performance liquid chromatography (HPLC).
- Gas chromatography (GC).
- Thin-layer chromatography (TLC).
Each of these variants aims to separate complex mixtures of substances present in biological material; however, GLC has found particularly wide application in the routine rapid diagnosis of specific infections.
Gas-Liquid Chromatography (GLC)
This method has become the gold standard for the rapid diagnosis of anaerobic infections.
The operating principle is based on the chromatographic detection of specific bacterial metabolic products directly within the test sample. During their vital activity, microorganisms release specific substances that can be instrumentally captured.
The primary metabolic markers for the presence of anaerobes are volatile fatty acids. By detecting them in a sample using GLC, a microbiologist can confirm the presence of anaerobic flora with a high degree of confidence, without waiting for the results of time-consuming culture growth.
Laser-Fluorescence Rapid Method
An alternative physicochemical approach relies on the optical properties of biological objects. The operational principle involves three key steps:
- Irradiation of the clinical material with a directed laser beam.
- Registration of the intrinsic fluorescence (so-called autofluorescence) of the studied material.
- Analysis of the emission spectrum. This spectrum is considered unique for most known microbes, as well as for their metabolic products.
The method is actively used in purulent-inflammatory diseases and various dysbioses. It is of particular value in dental pathology, assisting in the diagnosis of dental caries and periodontitis. Additionally, fluorescence evaluation is used to predict the efficacy of prescribed treatment.
Despite its high-tech nature, the method has a significant drawback — low specificity. The device registers light emission but is not always able to precisely differentiate closely related microbial species (unlike methods aimed at strict pathogen identification, viral load determination, or classical antibiotic susceptibility testing).