Georgia DUI Blog

Your hematocrit level is the ratio of aqueous portions and solid portions of your blood.  When alcohol enters your bloodstream it is carried in the plasma (liquid portion).  Alcohol does not get absorbed into the red blood cells and other solid material in your blood  Someone with a higher hematocrit level will have more solid parts in their blood and therefore will have less space for the alcohol to disperse in the liquid portion of the blood.  Normal hematocrit differences can elevate a BAC by 10% to 14%.

Blood drawn for a forensic blood test will in almost all cases be taken from the suspect via a vacutainer, which should contain two substances -sodium flouride, a preservative, and potassium oxalate, an anticoagulent. Further, they are vacuum sealed, which explains why they are called vacutainers .

Most vacutainers in use are made by Becton Dickinson. They also have an expiration date, after which the vacuum seal is no longer warrantied. BUT, very few phlebotomists, police officers, or state crime lab personnel pay any attention to the expiration date. Simply stated, nobody checks.

Becton Dickinson only checks one out of every four thousand vials for quality control. There are at least three possible defects in the state’s blood test:

1. A bad seal on the vacutainer, which is impossible to detect after the test, because it has been opened.

2. Improper amount of sodium flouride in the vial. Since vials are routinely nor refrigerated prior to their delivery to the crime lab, the proper amount of sodium flouride is critical. Either too much or too little can lead to a false high test result and

3. Improper amount of potassium oxalate. In the case of a bad seal organisms from the environment, such as candida albicans, can get in. Unless there is enough sodium flouride in the vial, the organisms that may be in your client’s blood will grow. One such organism is the ubiquitous candida albicans, which is is a yeastlike organism that is resistant to sodium floride. In the presence of glucose and warmth, it will excrete ethanol via fermentation.

Too much sodium flouride may cause “salting out”, which will also lead to a false high test result with headspace gas chromatography. This can occur even if there is no problem with the vacutainer, but the phlebotomist draws too little blood.

If there is not enough potassium oxalate, the blood can coagulate or “micro-coagulate” which is almost completly undectable. Because this changes the ratio of liquid to solid in the substance that is tested, and ethanol is water soluble, it can lead to a false high test result.

It can be virtually guaranteed that in any case involving a blood test the lab did not test for the presence of Candida Albicans, the lab did not check the vial seal, and the lab did not check the amount of sodium flouride or potassium oxalate in the tube.

If any of these occurred, you will in all likelihood have a false high blood alcohol concentration reported by the lab.

     If a person has taken methamphetamine, that individual should also have its metabolite amphetamine in their system. In other words, levels of both methamphetamine and amphetamine should be detected in both the blood and urine. Some GC/MS assays can falsely yield positive methamphetamine levels when high concentrations of ephedrine or pseudoephedrine are present in the specimen. Depending on the temperature of the injection port, the ephedrine or pseudoephedrine can be converted (or cooked) to methamphetamine. Therefore, sound scientific practice requires a negative report for methamphetamine if only methamphetamine is found in blood or urine. The absence of amphetamine means that the person had not consumed methamphetamine, which would in the ordinary course of metabolism would produce amphetamine. Therefore, in a case where only methamphetamine is found in the blood or urine the person probably had a cold and taken cold medicine containing ephedrine or pseudoephedrine.

Hospital laboratory testing of serum alcohol involves use of the enzymatic method. The enzyme kits do not measure alcohol directly. They oxidize alcohol to acetaldehyde by the reduction of NAD+ to NADH. The amount of NADH produced
is therefore a function of the amount of alcohol present in the sample, and the amount of NADH produced is measured via a color reaction. However, if the blood also contains high levels of lactate (lactic acid) from either the administration of Ringer’s Lactate or the release of lactate from damaged tissues and also high levels of LDH (lactate dehydrogenase) enzyme from damaged tissues, then it is possible that the NAD+ from the enzyme kits will also oxidize of lactate to pyruvate, thereby also producing NADH which would appear as “alcohol” in the test results. Therefore, it may be possible to have falsely high alcohol test results from serum alcohol tests using these hospital enzyme kits if both lactate and LDH are in high concentrations in the blood.

     If there is no anti-clotting agent in a tube used to collect blood, the blood will clot (due to the presence of fibrinogen in the blood).  Upon centrifugation of the tube, the clear yellow liquid at the top is called serum and contains little or no fibrinogen because the fibrinogen has been used up in the clotting of the blood cells.  A sample of the serum can then be removed for analysis of its serum alcohol concentration.

     If there is an anti-clotting agent in the tube, the blood should not clot if properly mixed (tube inverted a few times).  The tube can then be either shaken and a sample of the whole blood can be then be removed for analysis of its blood alcohol concentration, or the tube can be centrifuged.  Upon centrifugation of the tube, the clear yellow liquid at the top is call plasma and contains about 0.34 grams of fibrinogen per 100 mL of plasma.  A sample of the plasma can then be removed for analysis of its plasma alcohol concentration.

     Because serum and plasma only differ by the absence or the presence of a trace amount of the fibrinogen protein, the serum alcohol concentration and the plasma alcohol concentration should be essentially identical.  However, due to their higher water content than whole blood, the alcohol concentration in either serum or plasma should be about 18% greater than the actual whole blood alcohol concentration.

     No lab would try to measure the alcohol concentration in a blood clot which, because of its relatively low water content, would theoretically be relatively low in alcohol concentration compared to the whole blood alcohol concentration.