So you have a case where the state used expired blood tubes and they want to perform analytical chemistry for either Drugs of Abuse testing or ETOH testing. So what’s the big deal about that????
Well I am so glad that you asked….
Simple. Unlike what most people think it has nothing to do with the inorganic salts contained inside because the NaF and potassium oxalate remain stable in perpetuity. The expiration of the tubes surrounds the BD Vaccutainer warranty on the vacuum seal on the septa. If for example, the tube bears an expiration date of 2/10 then it is warranted to have the necessary pressure via evacuated vacuum pressure to fill to designated volume +/-1% (which in our case is typically designed for a 10ml draw so between 9 and 11ml) until the last day of February 2010. After that date, BD Vaccutainer does not warrant the seal of the septa and the vacuum pressure.
So what does this mean?
First what doesn’t it mean…. Frequently undereducated, non-technically trained, non-credentialed machine operators who are decidedly not analytical chemists will say that we know there is no issue as the tube contained blood. They might even say that it contained within the 10% tolerance and therefore even if past warranty it is still suitable for purpose. A kind of “no harm, no foul approach”.
The truth is that the opinion stated above is worth about as much as the imaginary degree in analytical chemistry that the machine operator has which is to day nothing.
3 major issues:
- Like most things in life, the integrity of the septa seal and the corresponding vacuum loss is not a binary concept (i.e., either gross failure or no failure), but rather a gradation along a spectrum of change in the integrity of the seal. So, therefore simply stating that we know there is no failure because we have collected blood within that 9 to 11 ml range is totally faulty logic. As one can easily imagine of a easy scenario that debunks this claim. Imagine the tube prior to expiration at full vacuum strength would collect 11 ml, but now with partial degradation only collects 9ml, then one can see a problem. It appears to have met the +/-10% but there has been and appreciable loss in the integrity of the seal manifested in the 9ml draw.
- If pressure can leak out (i.e., the integrity of the seal is compromised but not result in a gross failure), then “things” can get in. More technically stated, the introduction of Candida Albicans and exogenous alcohol production becomes a real potential issue. For a general discussion on the danger of Candida Albicans, I refer you to https://www.paduiblog.com/2010/01/articles/dui-testing/what-pacman-and-inflated-and-incorrect-blood-alcohol-content-results-have-in-common/ . Most crime labs do not perform a simple bacteria culture to rule in or rule out Candida Albicans. The introduction of Candida Albicans into the sample combined with a lack of proper refrigeration and also either an insufficient amount of the anti-glycotic agent (NaF) or a non-homogenized mixture of the anti-glycotic agent (NaF) (i.e., it is not properly inverted) may result in exogenous ETOH production due to petrification.
- Protocols exist for a reason. Expiration dates are not arbitrary. While 9 out of 10 times, you may get away with drinking milk past the date of expiration (which is an expression of how long the manufacturer of the milk warrants that the preservatives added into the milk will prevent curdling of the milk). There is that 10th time. Therefore, I prefer not to serve past expiration date items to my family. If I am not willing to so serve past expiration date items to my family, I will not likewise allow the power of the government to allow the police officers or Troopers to be rewarded for negligence, laziness or sub-standard actions.