health care instruments

Alcohol Testing Methodology

There are several different methods available for alcohol testing. Alcohol can be tested in the blood, breath, urine and saliva.

Blood Alcohol Testing

Blood Alcohol Concentration (BAC) is considered to be the standard for measuring the degree to which an individual is impaired by alcohol. For years, studies have shown that there is a direct correlation between the blood alcohol concentration and the degree to which reactions and judgments are impaired. The methodology used for blood alcohol testing is Gas Chromatography and is the most accurate forensic quality test in the industry today. However, drawing blood is an invasive and expensive procedure that most companies prefer to avoid.

Breath Alcohol Testing

It is well proven that there is a direct correlation between the blood alcohol concentration of a person and their breath alcohol contents. During respiration, gas is exchanged from the lungs to the blood (primarily oxygen) during inhalation, and visa versa (primarily C02) during exhalation. During this exchange, alcohol in the blood vaporizes and is carried out of the lungs in the exhaled breath. There are several types of breath alcohol testers available today. These range from disposable screening testers to the equipment that provides legally admissible results, including very expensive digital read-out breath alcohol monitors. These types of testers fall into three categories:

Evidential Breath Testing Devices
Non Evidential Portable Hand Held Devices
Disposable Devices (provides non forensic results)

The evidential breath testing devices are generally expensive (costs range from $2000-$5000 per unit), require regular maintenance, repair and calibration, and must be operated by certified personnel. Attachments such as sterile mouth pieces must be used each time a test is performed. These units are large table top units designed to be used in one location. Movement can cause a change in calibration which will require maintenance.
The portable hand held devices provide fairly accurate results and are used for screening purposes. By measuring the alcohol content in the breath, a reliable indication of the blood alcohol level is achieved. Portables devices are less accurate than evidential devices, however by comparing the cost performance ratio, these devices are affordable and sufficient for personal usage. Most potable devices are not evidential and therefore they cannot be used in the court of law.

The disposable devices are noninvasive, less accurate and non scalable methods of screening for alcohol. Can be used to detect the presence of alcohol with a rough estimate to the degree of impairment. Being disposable, the cost per test for preliminary screening is considerably higher than the cost of testing using portable devices.

Here is how they work The ethyl alcohol in the blood escapes through the lung tissue into the exhaled breath. The presence of ethyl alcohol in the breath is detectable by a color change of very sensitive chemically coated crystals contained in the Disposable Breath Analyzer. Immediately prior to use, the ampoule is ruptured by slight finger pressure on the outer flexible clear tube to release crystals within the confines of the tube. When the subject exhales into the tube, crystals interact with breath vapor and change color from yellow to blue if alcohol is present. If all the crystals change color completely, this indicates that the blood alcohol level of the subject is over 0.10%, exceeding the legal limit in most states.

Urine Alcohol Testing

Although urine alcohol testing will indicate the presence of alcohol of a person, it will not indicate the current condition of the individual. Once consumed, alcohol enters the blood through the stomach within 15 minutes, causing immediate impairment. It is then metabolized by the body and, after 1½ to 2 hours, will begin to show up in the urine. Therefore, urine alcohol does not measure a true condition of the person. The results indicate the condition several hours before.

Additionally, urine alcohol concentration does not directly correspond to blood alcohol concentration. Urine alcohol concentration will vary depending on the metabolism of the person and the amount of fluid in his system. For instance, a person who is slightly dehydrated will tend to have a higher alcohol concentration in his urine than someone who has a normal level of fluid in his system.

At least one study has indicated that a false positive for urine alcohol can occur. High levels of sugar and acetone in the body can cause fermentation in the urine, creating a false positive for urine alcohol. All things considered, the urine alcohol test is the least preferred or perhaps accurate test available for alcohol testing. It is worthwhile to read a supporting research paper published in THE AMERICAN JOURNAL OF CLINICAL PATHOLOGY: ERRORS OF CONVERTING A URINE ALCOHOL VALUE INTO A BLOOD ALCOHOL LEVEL. SIDNEY KAYE, PH.D., AND EDUARDO CARDONA, M. S.

Saliva Alcohol Testing

The second type of disposable tester available today tests the saliva for alcohol presence. Although a correlation between blood alcohol concentration and saliva alcohol concentration is believed to exist, the technology and chemical reaction employed has not been proven to be accurate or reliable.

Saliva testers are treated with an enzyme Alcohol Oxidize, which responds to alcohol in proportion to the concentration of alcohol in a mixed saliva sample placed on it. The user estimates the BAC by comparing the color change on the test strip patch to standard colors calibrated to correspond to different BACs.

Although some saliva testers seem to indicate the presence of alcohol fairly well, the enzyme alcohol oxidize used in these testers is easily effected by hot and cold temperatures. Hot temperatures will tend to indicate falsely high readings, while cold temperatures will tend to indicate falsely low readings. Exposure to temperatures above 80 degrees Fahrenheit or to ambient air will destroy the enzyme alcohol oxidize rendering the tester useless. Most saliva testers give no indication if contamination has occurred, they just will not work. Saliva testers generally have a shelf life of one year or less.

Additionally, most saliva testers do not have test results from independent laboratories.