Oral Fluid Testing

Drug abuse testing may be performed using saliva as the specimen. Mixed saliva or “oral fluid” comes from the salivary glands, oral mucosa and gingival cervices. Drugs from the blood are transported to the saliva by means of passive diffusion. Within just a few minutes, the drugs and metabolites present in plasma are distributed to the salivary glands and are diffused into the saliva after parenteral administration. Therefore, the concentration of the drug in the saliva is correlated with the drug concentration in blood. Saliva is capable of retaining trace amounts of drugs and its metabolites for about 24-36 hours. However, Alain Verstraete from Yale University had reported that upon consumption of opiates, it only takes about 5 hours up to 48 hours for it to become undetectable in saliva. 

SPECIMEN COLLECTION

Collection of saliva/oral fluid is quick, easy and non-invasive. It does not require the presence of medically-trained personnel and it can also be tested at the collection site such as in point-of-care devices. There are several methods in which saliva can be collected.

1. Unstimulated Collection

• Draining Method

Performed by letting the saliva drip from the mouth freely into the specimen container

2. Stimulated Collection

• Without the use of an external stimulus

Tongue, cheek or lip movements

• Chemical Methods

Performed by chewing paraffin wax, gum base or chewing gum

• Lemon drop or Citric acid

A lemon drop is placed in the mouth to serve as a gustatory stimulus for the production of saliva

Disadvantages of stimulated saliva production

The use of parafilm may produce erroneous results since this absorbs some drugs. This may also interfere with chromatographic analyses producing inaccurate results.

The use of citric acid may alter saliva pH and its drug concentration.

The use of cotton balls may also change immunoassay results.

Collection

After stimulation, saliva can be spit, swabbed, or suctioned from the mouth. Collection may also be performed by using absorbent materials (e.g. cotton balls). Saliva will be extracted from the absorbent material via centrifugation or pressure application.

TESTING

                

Saliva drug testing kits

Principle: Competitive Binding Prinicple

The test device contains an absorbent pad wherein the sample that contains the drugs and its metabolites compete with the drug conjugate that is immobilized on a porous membrane for limited antibody sites. As the sample flows through the absorbent pad, the free drug that is contained in the saliva binds with the labeled antibody-dye conjugate now forming an antibody-antigen complex. This complex competes with the immobilized antigen conjugate located in the “test” zone and will not produce a colored band when the drug exceeds the detection level. A colored band is formed in the “control zone” when the unbound dye conjugate binds with the reagent indicating that the device is functioning properly.

Procedure:

Strip Test

1. Bring both the kit and specimen at room temperature.

2. Remove test strip from the pouch.

3. Dip the strip into the container with the arrows pointing towards it.

4. The saliva should exactly reach the maximum line (no more, no less).

5. Hold the saliva until a reddish color is seen at the lower edge of the strip (approximately 10 seconds).

6. Withdraw the strip and place on a clean, dry surface facing up.

7. Read results within the span of time indicated in test pack.

Cassette test

1. Bring the test kit and specimen in room temperature.

2. Remove cassette from the pouch.

3. Place kit on a flat, dry surface.

4. Use the dropper to dispense 3 drops of saliva into the sample well.

5. Start timing and read results within the span of time indicated in the test pack.

Interpretation of Results:

Positive – presence of only one (1) colored band in the “control” zone

Negative – two (2) colored bands, one in the “control” zone and one in the “test” zone

Invalid result – no colored band formation in the “control zone”

ADVANTAGES

·         Cheap cost and convenient

·         Results may be interpreted immediately (approximately 5 to 15 minutes).

·         Donor-friendly and ease of collection

·         It can detect 8 different drugs up to 5 or 6 types at a time.

·         Mouth swab testing is the best method in detecting recent drug abuse.

·         It does not require medically-trained personnel for its performance.

DISADVANTAGES

·   This method is not approved by the Substance Abuse and Mental Health Services Administration (SAMHSA) for use in Federal Mandated Drug Testing.

·         Most drugs do not remain present in the person’s saliva and may not be detected after 12-24 hours of consumption.

·         It is less sensitive in detecting THC and Cannabinoids.

·         More expensive than urine testing.

·         False positive results may be seen in patients taking in medicines such as Ibuprofen, Motrin, and Advil.

·         Inferior compared with hair follicle drug testing.

·         Detox drinks and smoking are very effective in masking the presence of the drug and its metabolites in saliva.