Collection and Analysis of Oral Fluid
Oral fluid, a complex mixture produced by the salivary glands, provides a non-invasive biological matrix for diagnostic and monitoring purposes. It comprises secretions from the parotid, submandibular, sublingual, and minor salivary glands, along with crevicular fluid, epithelial cells, leukocytes, microorganisms, and food debris. Its composition reflects physiological states, making it suitable for detecting various analytes.
Composition and Properties
- Electrolytes: Contains sodium, potassium, calcium, chloride, and bicarbonate, impacting pH and osmolality.
- Proteins: Includes enzymes (amylase, lysozyme), immunoglobulins (IgA), mucins, and other proteins with antimicrobial and digestive functions.
- Hormones: Steroid hormones (cortisol, testosterone) and peptide hormones (growth hormone) can be measured to assess endocrine function.
- Drugs and Metabolites: Reflects systemic drug exposure, allowing for therapeutic drug monitoring and substance abuse detection.
- DNA and RNA: Contains genetic material from host cells and microorganisms, enabling genetic testing and pathogen detection.
Collection Methods
Several methods exist for collecting oral fluid, each with advantages and disadvantages regarding ease of use, volume obtained, and analyte stability.
- Passive Drool: Requires the individual to expectorate into a collection device. Simple but can yield variable volumes.
- Swabs and Sponges: Absorbent materials are placed in the mouth to collect fluid. Useful for individuals unable to expectorate but may require additional processing to extract the fluid.
- Stimulated Collection: Chewing gum or using citric acid can increase salivary flow, improving volume yield.
- Collection Devices with Volume Indicators: Specialized devices that provide visual confirmation of adequate sample volume.
Analytical Techniques
A variety of analytical techniques are employed to detect and quantify specific analytes in oral fluid:
- Immunoassays: Enzyme-linked immunosorbent assays (ELISAs) and lateral flow assays are commonly used for rapid detection of antibodies, drugs, and hormones.
- Chromatography: Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) provide sensitive and specific quantification of drugs, metabolites, and other organic compounds.
- Molecular Diagnostics: Polymerase chain reaction (PCR) and other molecular techniques are used for detection and quantification of DNA and RNA targets, including pathogens and genetic markers.
- Electrochemical Sensors: Used for real-time monitoring of specific analytes, such as glucose and electrolytes.
Applications
- Drug Testing: Detection of illicit drugs and monitoring of prescription medications.
- Hormone Analysis: Assessment of adrenal function (cortisol), reproductive hormones (testosterone, estrogen), and growth hormone.
- Infectious Disease Diagnosis: Detection of antibodies or viral RNA for HIV, hepatitis, and other infectious agents.
- Genetic Testing: DNA analysis for disease risk assessment, paternity testing, and pharmacogenomics.
- Oral Health Assessment: Analysis of salivary enzymes and proteins for monitoring periodontal disease and caries risk.
- Therapeutic Drug Monitoring: Measurement of drug concentrations to optimize dosing and ensure therapeutic efficacy.