GENERAL LABORATORY NOTES for TOXICOLOGY
Studies have shown
that thixotropic gels (serum separators) and plasticizers interfere with drug
recovery and quantitation. Therefore serum separator or plastic tubes
should not be used for either toxicology or therapeutic drug monitoring
laboratory does not preserve chain of custody for specimens. hence, forensic
studies (including forensic alcohols) should not be submitted to this
laboratory. Instead, such samples should be submitted directly to the
appropriate legal entity.
Blood samples are saved for one week in the laboratory while urines are retained
for three days. Additional (add-on) tests should be requested within these
windows, if needed.
It should be noted that the urine immunoassay drug panel is merely a general
screen for drugs and drug classes. If it yields positive results, these should
be considered to be presumptive only. The urine comprehensive drug panel
includes a broad spectrum search for multiple drugs and drug classes. Positive
results are confirmed whenever possible. It should be emphasized that, due to
its small size and limited scope, the urine immunoassay drug panel may fail to
detect many important drugs, including but not limited to tricyclic
antidepressants, meperidine, phenothiazines, etc. A detailed listing of the
constituents of the urine immunoassay drug panel and the urine comprehensive
toxicology panel is included in the Toxicology tables that follow.
It should be noted that the plasma alcohol screen is a non- specific screen for
ethanol and generally fails to detect other alcohols such as methanol and
isopropanol. If the latter agents are suspected, please order the alcohol panel
(which includes a quantitative measurement of methanol, ethanol, acetone, and
isopropanol). If ethylene glycol is suspected, please order it specifically
since it will not be detected by neither of the above.