Saliva as a diagnostic fluid DENT 5302 Topics in Dental Biochemistry Dr. Joel Rudney
Saliva as a diagnostic fluid
DENT 5302
Topics in Dental BiochemistryDr. Joel Rudney
Why use saliva?
Collection is relatively non-invasive - no needles! Range of potential analytes as broad as plasma
Bacteria in saliva Salivary ions Secreted salivary proteins Inflammatory mediators Proteins, metabolites, from other parts of the body Nucleic acids (from the mouth and other regions)
This is considered a high-priority research area The vision - chairside diagnostic testing
The search for biomarkers
A big buzzword in diagnostics today Any sort of analyte can be a biomarker The keys to the definition
Changes in a biomarker must be associated with the active presence of a disease, or future risk of a disease
There doesn’t have to be a direct etiological relationship
A marker for risk or diagnosis Multiple analytes can improve sensitivity/specificity
Earlier efforts - caries risk
Bacteria in saliva as biomarkers - chairside tests Dentocult SM® "Strip mutans", S. mutans in saliva Dentocult LB®, Lactobacilli in saliva
Dentobuff® test strips, salivary buffering capacity (HCO3-)
General problem - high sensitivity, but low specificity Combination testing (all three plus flow rate)
Not much improvement These products not widely used in the U.S.
Other oral diseases
Detect candidal infection - Oricult N® Not widely used in the U.S.
Periodontitis The major focus is on biomarkers in gingival fluid Periodontists want to predict which sites will lose
attachment Saliva can only provide indirect indications
Saliva drug testing
Main focus is drugs of abuse Much less invasive than observed urine testing
Harder to fake, no oral equivalent of the “whizzinator” Products for “roadside” forensic testing
Rapiscan ®, Oral-Screen™, 4-5 drugs simultaneouslyCannabinoids, opiates, meth, cocaine, diazepinesSome published validation of these methods
Largely unregulated online offers for home testing Matched by online offers of products to beat the tests No real validation of either
Saliva and steroids Passively carried into saliva with water from plasma Accurately correlated with plasma levels Monitoring of female reproductive hormones
Convenient for monitoring therapeutic usesPost-menopausal HRTMenstrual cycle timing
Saliva and androgens Can be used to monitor testosterone levels
HRT, but also by bodybuilders Steroids of athletic abuse (with the right test system)
Also lots of online activity
Saliva and HIV testing
Extremely low levels of virus relative to other body fluids Assumed to be due to anti-viral salivary proteins
SLIPI, MUC7 Antibodies to HIV (protective or not?) are present
The basis for HIV testing in saliva Saliva-based home HIV test on track for approval
Controversial issuesPro - more people will get tested, seek treatmentCon - no counseling, outside the public health system
Sjogren’s Syndrome proteome Early detection of salivary gland changes Previous studies of individual proteins
Differences, but sensitivity/specificity inadequate Can this be improved by comparing proteomes? Recent data from NIDCR
Compared to controls, patients show:Incr. inflammatory proteins: lysozyme, lactoferrin,
cystatin C, 2-microglobulin, Ig -light chain, polymeric Ig receptor (component of S-IgA)
Decr. acinar proteins: presumed PRPs, amylase, carbonic anhydrase
Key question: How early do these changes begin?
Cancer antigens in saliva
Breast cancer biomarkers Salivary c-erbB-2 protein - an oncogene product Elevated in breast cancer patients
Sensitivity = 87%, specificity = 65% Proteomic studies in progress
Not useful for prostate-specific antigen (PSA)
Saliva and oral cancer
The earlier the diagnosis, the better the prognosis Dentists are the first line of defense Oral cancer is hard to distinguish from transitory lesions
When should you biopsy? Can pre-cancerous conditions be detected? Can salivary biomarkers provide an earlier warning?
An area of active research at U of M
Many potential biomarkers
Elevated levels of certain bacteria in saliva Three very common commensal species
Capnocytophaga gingivalis, Prevotella melaninogenica, and Streptococcus mitis
Probably effect rather than causeSensitivity = 80%, specificity = 82%
Proteomes, genomes, and transcriptomes Dr. David Wong at UCLA School of Dentistry
Collaborators at U of M• Drs. Nelson Rhodus and Patrick Gaffney• Dr. Kathy Moser (Sjogren’s)
Findings from the Wong lab
Oral cancer biomarkers in the salivary proteome Elevated levels of the proinflammatory cytokine IL8
A general marker of inflammationOther sources of oral inflammation - confounders?Additional protein biomarkers may be needed
Oral cancer biomarkers in the salivary transcriptome Wong lab discovered that saliva contains “intact” mRNA Marker of changes in gene expression due to cancer? Seven genes upregulated in patients relative to controls
Includes two proinflammatory cytokines, IL8 and IL1
Chairside testing
Wong lab is collaborating with engineers Objective: “lab on a chip”
Miniaturized multi-analyte detection and quantification Intended for use in a dental office Results at chairside
Application: Identify patients to watch or biopsy Detect oral cancer while it is still treatable
The same concept can be applied to other diseases Oral and systemic diseases both People see dentists more often than physicians The hunt for biomarkers is ongoing
Format of the saliva midterm
Short-answer questions How Dr. Rudney defines a short answer:
When I say short, I mean short Some of them can be answered with a single word.
Respond with words, phrases, or diagrams, as seems appropriateDon’t mess around with complete sentences or essays.Use only the space provided for each question.
In the case of questions worth more than one point:The number of points given will be based on the number of
correct answers you provide for that questionWhen I ask for examples, it means that the number of potentially
correct answers is greater than the number of examples that I’m asking for.
There are no trick questions (at least, not intentionally)
A sample one-point question
Q. Identify the component of the water secretion system that requires energy to function. (1 pt.)
A sample one-point question
Q. Identify the component of the water secretion system that requires energy to function. (1 pt.)
A. Na+-K+-ATPase
You get one point
A sample multi-point question
Q. Give three examples of proteins found in pellicle (3 pts.)
A sample multi-point question
Q. Give three examples of proteins found in pellicle (3 pts.) A. Statherin, acidic proline-rich proteins (aPRP), histatins
You get three points
A sample multi-point question
Q. Give three examples of proteins found in pellicle (3 pts.) Acceptable answers:
Statherin, acidic proline-rich proteins, amylase, histatins, cystatins, MUC7 mucin, lysozyme, albumin, carbonic anhydrase
Use any three, and you get three points
A sample multi-point question
Q. Give three examples of proteins found in pellicle (3 pts.) Acceptable answers:
Statherin, acidic proline-rich proteins, amylase, histatins, cystatins, MUC7 mucin, lysozyme, albumin, carbonic anhydrase
Your answer: Statherin, aPRP, basic PRP
You get two points