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Problems in Blood Testing

If you were arrested for DUI and subjected to a blood test, the sample will be tested in an attempt to estimate its blood alcohol concentration. Before trial, your criminal defense attorney will fight to have the blood excluded from evidence. In the event, your blood test result is admitted at trial, your attorney will explain to the jury all of the reasons that the blood test results are not accuarate and reliable.

The biggest problems in testing for blood to determine its alcohol concentration can include:

  • clotting;
  • hemolysis; and
  • hemoconcentration.

Clotting Problems in Blood Testing

Clotting is the result of a biochemical reaction by which blood coagulates, changing from a liquid to a gel. When blood has completely clotted, the liquid portion that is separated from the clot is called serum. A blood clot changes the composition o f the blood sample.

Using the wrong size and type of needle can cause blood to clot. For example, Blood that is collected with a small butterfly needle, including a 25-gauge needle, has a higher chance of clotting than blood collected with 21-gauge straight needle. Since it takes longer for blood to flow through a 25-gauge butterfly needle and its tubing, as compared to a larger straight needle, clots can form in the tubing.

The tubing does not contain any anticoagulant. Microdots that form in the tubing can pass into the glass collection tube. The anticoagulant contained in glass collection tube will not dissolve clots that have already formed; it is only meant to prevent clots from forming.

Clots can also occasionally form inside the glass blood collection tube, even when the tube contains an anticoagulant. Clotting inside the collection tube usually indicates a problem with the blood collection process. Removing a clot is against best practices and does not fix the problem with the sample.

Clotting can render blood alcohol analysis unreliable under the gas chromatography method, the method that all FDLE permitted labs currently use.

Clotting artificially elevates the alcohol content in a blood sample because it changes the ratio of liquid to solid. Alcohol follows water and other liquids, like plasma. When a sample contains more plasma than the "whole blood" flowing through the body, the alcohol content in the sample will be higher than the alcohol content in the body. In addition, clots can clog the pipette used to take a sub-sample of the blood for testing, rendering the sample unreliable for testing.

A sample that is grossly clotted is not a good representation of whole blood alcohol content. Testing this kind of sample would increase the blood alcohol content under the gas chromatography method.


Problems with Hemolysis in Blood Testing

Hemolysis is the act of breaking a red blood cell open. Hemolysis destroys red blood cells, releasing their contents into the liquid portion of the blood. Hemolysis can occur for various reasons, including using the wrong needle and improper tourniquet use. For example, many blood samples that are collected using a 25-gauge butterfly needle will have some degree of hemolysis, usually significant hemolysis.

Hemolysis can also occur if the needle enters the vein at a shallower angle.

Hemolysis can also occur because of the misapplication of a tourniquet, such as leaving it on too long. Best phlebotomy practices dictate that a tourniquet should be removed within one minute of its application. Using a 21-gauge needle and proper use of the tourniquet substantially reduces the chance of hemolysis.


Testing for Hemolysis Using Centrifuging

Hemolysis is not visible to the naked eye. To test for hemolysis, a portion of the blood sample must be centrifuged so that the liquid (plasma) separates from the solid parts of the blood. The plasma sample is then compared to a hemolysis color chart to determine the degree of hemolysis. The darker the sample, the greater the degree of hemolysis.

Centrifuging does not disrupt the blood alcohol testing process because it uses only a portion of the sample, takes minutes, and is performed with standard laboratory equipment.


Testing for Hemolysis in a Hospital Setting

Hemolysis is the single biggest issue with blood sample integrity. In hospitals, every blood sample that comes into a laboratory is inspected for hemolysis. The analysis can inspect the sample for hemolysis by documenting the degree of hemolysis in the laboratory notes.

The biggest cause of hemolysis in the blood samples is error in the blood collection process.

A blood sample with a significant degree of hemolysis is an unreliable sample for testing under the enzymatic method because hemolysis artificially raises blood alcohol levels.


Impact of Hemolysis on Testing for the Blood Alcohol Concentration

Since hemolysis breaks open red blood cells, changing the color of the blood, and the enzymatic method is color-dependent, a sample with significant hemolysis produces inaccurate blood alcohol results.

The effect of hemolysis on the gas chromatography method can lead to a dramatic increase in the reported alcohol concentration because a hemolyzed sample is not representative of the blood circulating in the person tested.


Hemoconcentration Problems in Blood Testing

A problem can occur in Blood Alcohol Concentration Testing because of Hemoconcentration. Hemoconcentration is defined as the loss of fluid to the tissues that results in an increase in the concentration of red blood cells.

Hemoconcentration allows more plasma to go through the needle into the blood sample than is contained in the blood circulating in the subject's body. Hemoconcentration increases the alcohol content in a blood sample because it raises the water content in the sample, and alcohol follows with water.

Hemoconcentration can result from applying the tourniquet for too long, or from using of the wrong needle.


DUI Lawyers for Blood Testing in Florida

If your DUI cases involves blood testing, then contact an experienced DUI defense lawyer in Florida. The attorneys at Sammis Law Firm in Tampa, FL, are experenced in represent clients throughout the Tampa Bay area. Call us for a free consultation to discuss your case.

Find out more about the charges pending against you, the method used to for blood testing after a DUI arrest, and defenses that might apply to your case. Call 813-250-0500 to discuss your case.


This article was last updated on Thursday, January 5, 2017.