Transcript Sample transfer and storage

IN THE NAME OF GOD
‫بسمه تعالی‬
‫آزمایشگاه مرجع سالمت‬
Sample & Sampling for Toxicological
Analysis
Seyed Ali Nazeri
[email protected]
INTRODUCTION
At least six different test groups are required to be analyzed
to exclude even the most commonly encountered poisons.
Group Tests
•
•
•
•
•
•
Group 1: Gases
Group 2: Volatile substances
Group 3: Metals
Group 4: Drugs
Group 5: Pesticides
Group 6: Miscellaneous substances
TOXICOLOGICAL ANALYSIS OF TISSUE
•Collect biological samples from organs and tissues.
•A forensic toxicologist cannot simply look for the presence of a
toxin or drug in a body, she must understand how the body
processes these molecules.
•Toxicological analysis must start as soon as possible after a
person’s death.
SAMPLE & SAMPLING FOR TOXICOLOGICAL
ANALYSISA
Issues in Specimen Collection
•Selection
– Multiple, varied sites of collection
• Collection
– Appropriate method of collection
– Adequate volumes for analysis
• Storage and handling
Types of samples
• The specimens available for analysis may be numerous,
they include:
• Biological Samples
• Non-Biological Samples
Postmortem biological samples
1- Stomach Content (all available)
2- Blood (20-30 mL, 10 mL)
3- Urine (all available)
4- Liver (250 gr)
5- Kidney
6- Vitreous Humor (all available)
7- Bile (all available)
8- Muscle (10 cm3)
Biological Specimens
Urine
• Qualitative - the presence of a drug in the urine of an individual
indicates that some time prior to death the drug or poison was
present in the blood of the individual.
• Stomach contents
• Stomach contents may contain unabsorbed poisons, tablets, capsules,
caplets which may be intact and visible.
• These can be removed from the stomach contents, and identified.
Urine Testing: The Most Commonly Used Drug Test
•
Bile
• Since it is produced by the liver, it is similar in respect to the
liver samples in that concentrations of drugs in the bile are
usually greater than concentrations in the blood.
•
Liver
• According to it’s structure, which contains metabolizing
enzymes and fat, It is the best tissue sample for toxicological
analysis
Vitreous humor
• Vitreous humor is in a protected position behind the lens of the eye.
• Because of this protected position, it is isolated from putrefactive
processes, from charring and from trauma.
• Vitreous fluid is less susceptible to these effects, particularly because it
is likely to be free from microorganisms
Blood
• The potential for postmortem ethanol formation complicates the
interpretation of ethanol-positive results.
• Sodium fluoride is the most commonly used preservative for
postmortem specimens.
• Sodium fluoride protects blood from postmortem changes
such as bacterial production of ethanol or other alcohols.
• It also helps to protect other labile drugs such as cocaine,
nitrazepam and clonazepam from degradation.
Fluoride and enolase activity
The fluoride ion is seemingly effective in inhibiting the
activity of several kinds of enzymes, such as enolase a
component in the glycolytic pathway, and is important for
the action of yeasts, fungi and many micro-organisms
responsible for fermentation.
Hair
• Since hair grows at a predictable rate (generally 1 cm/month)
can be used to provide a historical record of drug or poison
exposure.
• Procedure is to chop a hair sample into 1 cm increments and
analyze them separately to “track” drug exposure over a long
period of time.
Biological samples in alive persons
• Urine and blood samples should be collected as soon as
possible in suspected opioid and alcohol abuse.
Non-biological Specimens
Non-biological submissions
• Used to direct analysis of biologicals
• May indicate the nature of substances that may have
been ingested, inhaled or injected
• Examples:
– Containers found at the scene
– Syringes
– Unidentified tablets or liquids
Non biological samples
• Tablets
• Ampoules
• Powders
• Capsules
• Drugs of abuse
• Syringes
• Food & Beverage Residues
Storage and Handling
Proper specimen handling
• Identification of samples
– Continuity
– Contents
• Specimens delivered to lab without delay
• Specimens should be analyzed as soon as possible
• Storage areas should be secure
Storage and Handling
• Not feasible to analyze specimens immediately
• Sample should be in well-sealed container
• Sample containers must be sterile
• Use of preservatives and anti-coagulants
• Refrigeration vs. Freezing
– Both inhibit bacterial action; esp. freezing
– Freezing results in  prep time
– Freeze-thaw cycle may promote breakdown
Storage of Samples
• Preservative
– Sodium fluoride
• Anti-coagulants
–
–
–
–
Sodium citrate
Potassium oxalate
EDTA
Heparin
• Anticoagulants are not really necessary in postmortem blood
samples since the blood is hemolyzed.
Sample transfer and storage
• Sample transfer and storage
Evidence collected from the victim of a suspected DFC must be properly •
sealed
and secured. Biological specimens should be stored at 2-8 °C to help •
prevent
degradation. Specimens should be transported refrigerated to the •
laboratory as quickly as possible; in any event minimizing the time they are
kept at temperatures above 25 °C.
Sample transfer and storage
Whole blood •
Blood should be collected in addition to urine, preferably within 48 hours of the alleged •
incident. Blood sampling should be performed with disposable syringes; the use of ethanol
or other solvents with volatile fractions should be avoided in skin disinfection. At least two
5 ml samples should be collected in blood tubes containing compounds such as NaF and
potassium oxalate (recommended concentrations for NaF 2.5 g/l and potassium oxalate 2
g/l) to prevent degradation and clotting with one sample used for analyses and the other
retained in case of a need for a defence analysis. The blood samples should be refrigerated
(at 2-8°C) as soon as possible. If it is not possible to conduct analysis within 24 hours, it is
advisable to preserve the sample by storage in a freezer (after separating the plasma).
Furthermore, it is advisable that sample residues are stored in a freezer (–18 °C) in case
further analyses are requested at a later date. In cases where blood plasma may need to be
separated by centrifugation from blood cells prior to analysis, the separation should be
done before the freezing of whole blood.
It should be noted that the timeframes provided for detection of drugs in urine and blood •
are general guidelines and that many drugs will no longer be detectable in conventional
samples such as urine, four or five days after ingestion
Sample transfer and storage
Head hair •
In cases of late reporting of the alleged assault or if chronic exposure to a drug must be assessed, •
head hair should be collected at least four weeks after the alleged assault. At least two hair samples
(thickness of a pencil) should be cut as close to the scalp as possible (see the figure 1 in annex 5). It is
very important that hair is sampled in a strict manner by properly trained personnel. A sampling
protocol is given in annex 5. In cases of a shaven head, pubic, axillary, torso or leg hair may also be
collected for analysis, although the interpretation of the quantitative results in these cases remains
very difficult.
When segmental analysis is not possible (if only axillary, torso or leg hair are available), analysis •
could be eventually limited to a qualitative analysis, because the growth rate is not well established,
as happens in head hair. Consequently, a positive result in these type of hair samples indicates that
the alleged victim consumed the compound at any time, but not necessarily at the time of the
assault.
Hair samples should be stored at room temperature, in a dry environment protected from light •
Sample transfer and storage
Other biological samples •
In some cases, vomit from the scene of the alleged •
assault or from the clothes of the complainant may be a
useful specimen. If a drug is not fully absorbed before
vomiting occurs, the drug may be detected at relatively
high amounts in a vomit stain. If collected, vomit or a
vomit stain should be stored preferably frozen.
Sample transfer and storage
Biological samples and sampling Urine
Urine should be collected in any case in which the complainant reports •
within the first 120 hours (5 days) after the alleged assault. While in
reality many of the drugs listed in annex 1 may have been eliminated
from urine in less than 120 hours, a few may remain at low
concentration.
A minimum of 50 ml of urine should be collected in at least two sterile •
containers (no preservative needed) and stored at 2-8 °C. If it is not
possible to analyse samples within 24 hours, it is advisable to store the
samples in a freezer (–18 °C). Unused samples should be stored in a
freezer in case further analysis is requested for at last 12 months
Sample transfer and storage
Other samples •
If the scene of the alleged assault is searched, cups, drinking glasses, bottles, containers •
and liquids that may contain residues of drugs should be collected and submitted for
analysis. Other items of evidence that could prove useful to the investigation include
plates, foods, pharmaceutical products and prescriptions for medicines.
Photographic/video (cameras, video recorders) and electronic evidence from computers
may also prove useful to the case as there have been several instances when the
perpetrator(s) have recorded the assault. For trace evidence, clothing, sheets and bedding,
sexual devices, condoms, etc. should be collected with the classical precautionary measures
for DNA analysis.
Police and crime scene investigators are normally trained to collect such evidence. Care •
should be taken that scene residues are packed individually in order to avoid crosscontamination of biological samples, especially if volatile compounds are implicated in the
alleged assault
‫گردهمایی کارشناس مسئولین آزمایشگاههای بهداشتی دانشگاههای علوم پزشکی کشور ‪ 9 -10‬آبان ‪94‬‬