Biomarkers in Medicine and Periodontology

Vocabulary practice flashcards generated from the lecture notes on biomarker concepts, validation stages, cancer classifications, and periodontal diagnostic markers.

Biomarker (FDA Definition)

A characteristic that is objectively measured and evaluated as an indicator of normal biologic, pathogenic, or pharmacologic responses to therapeutic intervention.

Types of biomarkers

Molecular (ex. Blood glucose), histologic, radiographic (ex tumor size), physiologic (blood pressure)

What can biomarkers tell us?

Disease, biological processes in the body (HR, blood pressure, temperature), response to treatment / medication, psychological condition

Characteristics of ideal biomarker

High sensitivity, specificity, accuracy, high predictive value. Safe and easy to measure. Cost-efficient to follow up. Modifiable with treatment. Consistent across gender and ethnic groups.

Surrogate Endpoint

A laboratory measurement or physical sign used in clinical trials as a substitute for a clinical endpoint to indicate a drug's therapeutic response, benefit, or harm.

Predictive Biomarker

A marker used to stratify patient populations into responders and non-responders, forecasting whether a specific drug will be effective or toxic.

Prognostic Biomarker

A biomarker that predicts the overall clinical outcome, disease recurrence, or risk of progression in a patient population independent of specific therapy.

Efficacy Biomarker

A biological marker used to demonstrate a measurable response in treated subjects, categorized into surrogate, predictive, pharmacodynamic, and prognostic endpoints.

Phase 1 Biomarker Evaluation

The initial discovery phase where candidate markers are identified and prioritized based on their diagnostic, prognostic, or therapeutic clinical value.

Phase 2 Biomarker Evaluation

The evaluation phase where a specific clinical assay is established and validated for reproducibility and laboratory portability.

Phase 3 Biomarker Evaluation

The evaluation phase assessing test sensitivity and specificity for detecting preclinical disease before clinical diagnosis occurs.

Phase 4 Biomarker Evaluation

The phase evaluating test sensitivity and specificity on a prospective cohort to determine false referral rates and disease characteristics.

Phase 5 Biomarker Evaluation

The final evaluation phase assessing the overall population benefits, risks, and clinical utility of a screening diagnostic test.

Categories of Cancer Biomarkers

Classifications of cancer markers based on disease state (prediction, detection, diagnosis, prognosis), biomolecules (DNA, RNA, protein, glyco), and other criteria (imaging, pathological, in silico).

Gingival Crevicular Fluid (GCF)

An oral fluid exudate or crevice cleanser containing over 65 evaluated constituents used as potential diagnostic markers of periodontal disease progression.

Saliva

A non-invasively collected oral fluid secreted by parotid, submandibular, and sublingual glands containing water, enzymes, antibodies, ions, and mucins.

Alkaline Phosphatase (ALP)

A salivary enzyme associated with alveolar bone loss that demonstrates elevated activities in the mixed saliva of adult periodontitis patients.

Interleukin-1$\beta$ (IL-1$\beta$)

A proinflammatory cytokine found in GCF and saliva that stimulates osteoclastic activity, immune cell recruitment, and tissue destruction.

C-Reactive Protein (CRP)

An acute-phase inflammatory protein synthesized in the liver that enters saliva via GCF and is elevated in chronic and aggressive periodontal disease.

Matrix Metalloproteinases (MMPs)

Key host-derived collagenolytic enzymes, such as MMP-8, responsible for extracellular matrix degradation and indicating periodontal disease activity and severity.

Beta-Glucuronidase

A hydrolytic enzyme present in saliva and GCF that degrades connective tissue ground substance and correlates with periodontopathogens like P. gingivalis.

Aspartate Aminotransferase (AST)

An enzyme marker of active cell death within periodontal tissues, serving as an indicator of periodontal disease activity.

Neutrophil Elastase

A proteolytic enzyme marker of intracrevicular polymorphonuclear leukocyte (PMN) activity that exhibits antibacterial properties.

Osteocalcin

An osteoblast-derived calcium-binding bone matrix protein that promotes hydroxyapatite accumulation and attracts osteoclast progenitor cells.

Osteopontin

A non-collagenous bone matrix protein secreted by osteoblasts and osteoclasts that accumulates at attachment sites to regulate bone maturation.

Tumor Necrosis Factor-$\alpha$ (TNF-$\alpha$)

A cytokine produced by mononuclear phagocytes in response to bacterial LPS that induces bone resorption and collagenase production while inhibiting collagen synthesis.

Interleukin-6 (IL-6)

A cytokine produced by monocytes, macrophages, and fibroblasts that promotes B cell maturation, antibody secretion, and osteoclastic bone resorption.

Interleukin-17 (IL-17)

A proinflammatory cytokine produced by T-helper 17 cells that stimulates secondary inflammatory mediators and drives osteoclastic bone resorption.