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How long does a blood toxicology sample last after the test is completed?

Dec 2012
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Answered by

General & Family Physician
Practicing since : 2012
Answered : 1704 Questions
How long does a blood toxicology sample last after the test is completed? I had a tox. screen 1 1/2 years ago and it came up for cocaine which I do not do. My doctor said it came up a false positive because of all the psych. medications I take. They now want to redo the test with the 1 1/2 year old sample. Is that sample still viable after all this time?
Posted Fri, 25 Oct 2013 in Medicines and Side Effects
Answered by Dr. Nsah Bernard 2 hours later
Brief Answer:
Depends on preservation

Detailed Answer:

Thanks for posting on XXXXXXX

The viability of the sample will depend if the laboratory that is in charge actually preserved the sample in good conditions i.e will not permit environmental conditions of temperature and pressure to influence the chemical composition of your blood sample which could actually alter the sample results. Toxicology results are measured in concentrations i.e unit per volume.
I wonder why they do not just take another sample from you now and do the testing or perhaps they wish to compare previous (actual results) with present results. If they have developed new testing techniques they would still have a point trying to use the previous sample. But in my personal opinion I doubt if the results will actually be valid given that the sample have gone through 1.5 years.

Hope this helps and wish you the best. Do feel free to update me with a follow-up.

Dr. Nsah
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