Types Of Testing Blood Urine And Hair Specimens

Blood and urine are the most commonly used biological fluids in the analysis for drugs other than alcohol. Blood, obtained by an invasive procedure, is available only in small quantities and drug concentration levels in blood are typically low. Urine is the preferred sample of choice as it is available in larger volumes, contains the metabolite and requires less invasive procedures in its collection. Both sampling procedures, however, are limited in their ability as they only determine the absolute amount of drug present in the fluid being examined. This quantity is dependent upon the amount of the drug used, when it was last used, as well as the half-life of the drug.

Recently, hair samples have been used to detect drug use. A number of technical problems must be overcome before hair can be used as a definitive proof of drug use. Hair treatment and environmental absorption are but two of the many concerns and problems that have been cited. An advisory committee of the Society of Forensic Toxicology has recently reported that ''The committee concluded that, because of these deficiencies, results of HAIR ANALYSIS alone do not constitute sufficient evidence of drug use for application in the workplace.''

Various body fluids such as sweat, saliva, blood, urine and breath, have been used for alcohol analysis. Breath, though not a body fluid, is commonly used by law enforcement authorities. Although a number of variables can effect breath/blood ratio, a 2100:1 alveolar breath/blood conversion ratio has been used and accepted for use with BREATHALYZERS. Breath-testing equipment calibrated with a blood:breath conversion factor of 2100 consistently underestimate actual BLOOD Alcohol Concentrations (BAC). Accuracy of breath analysis results is subject to various instruments and biological factors. Potential errors in breath analysis can also be caused by the presence of residual alcohol in the mouth. Immediately after drinking there is enough alcohol vapour in the mouth to give artificially high concentrations on breath analysis. Generally this effect disappears twenty minutes after drinking but high values for as long as forty-five minutes have been reported.

As of the early 1990s, all existing technologies are limited in terms of determining how much or when the drug was consumed.

Blood and saliva concentrations reflect the current blood alcohol concentration, but generally a blood sample is used in hospitals to access the patient in the casualty wards. In programmes requiring monitoring of alcohol use, urine is probably the sample of choice. Urine alcohol concentration, which represents the average blood alcohol concentration between voiding, has the potential of being ''positive'' while the blood may be ''negative.''

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