Tag Archives: biochemistry

COLLECTION, PRESERVATION AND EXAMINATION OF BIOLOGICAL SAMPLES

By @forensicfield

Introduction

There are several challenges to select and collect samples for antemortem and postmortem analysis. The relevance of any finding is primarily determined by the type and quality of the sample submitted to the laboratory that’s why numerous pre-analytical aspects should be considered during collection in order to have samples with sufficient quality and quantity.

How to collect and preserve biological samples? and, in what amount biological samples are needed for examination? All information is given below:

✴VISCERA

✔ Viscera Is The Internal Organs Of The Body.
✔ Specifically Those Within The Chest As The Heart Or Lungs Or Abdomen As The Liver, Pancreas Or Intestines.
✔ Viscera Comes From The Latin Word Viscus, Meaning “An Inner Part Of The Body.”

✴BLOOD

🔴 Peripheral Vein blood (Femoral, Jugular, Sub-clavian) is preferred.
🔴 Blood can be syringed out or can be taken after opening the veins. Sample should be kept in a screw cap bottle containing Sodium Fluoride (NaF) and Potassium Oxalate.
🔴 100mg of NaF and 30 mg of Potassium Oxalate to 10ml of blood should be added.
🔴For toxicology, basically serum is utilized for toxicological screening and cellular sediments are discarded.
🔴 In the case of Cocaine, plastic bottles should be avoided.
🔴 In cases of CN and CO airtight cap should be used.
🔴 In cases of volatile poisons a thin layer of liquid paraffin is advised over the top of collected fluid to avoid evaporation.
🔴 For insulin and Cortisol levels- Serum should be separated immediately.

✴URINE

🔘 Catheter samples or Supra pubic puncture samples can be collected from urinary bladder.
🔘 100mg sodium fluoride for every 10 ml of urine is recommended. 30 ml in NaF or thymol is desirable quantity.
🔘 A pinch of Phenyl curate and little Thymol should also be added in urine samples as a preservative.

✴BILE

✅ It is suitable for Morphine and other Opioids, Drugs like Chlorpromazine.
✅ It can be obtained after opening of gall bladder or full gall bladder with adjoining tissues can be kept for analysis.
✅ Bile may be extracted in 20 ml wide mouth bottle as it is thick fluid and normal preservative NaF can be added if there is delay in chemical analysis.

✴VITREOUS

✔ It should be aspirated into a syringe with a wide bore needle especially when blood is not available due to decomposition.
✔ This is mainly used for sugar, electrolytes, urea and creatinine estimation.
✔ It can also be used for toxicological analysis.
✔ A portion of the vitreous should be preserved with NaF on similar way as for blood samples. After taking sample , fill equal amount of water or saline so that eye can retain its original shape and contour.

✴CEREBROSPINAL FLUID

✅ This is mainly used for microbiology and virology.
✅ Lumbar puncture, cisternal puncture before dissecting the body or from the space in front of Pons after the opening of skull but before removing the brain or from the lateral ventricles can be performed to collect CSF.
✅ NaF should be added for toxicological analysis.

✴STOMACH CONTENTS

✅ Open via greater curvature and collected in to wide mouth jar without contamination. Container with screw cap lid is used.
✅ Preservative is added, if there is delay before sending to Laboratory.
✅This is used when ingestion of poisons or drug over dose is suspected.
✅Chemical analysis is indicated when heavy metal poisoning is suspected. (Arsenic, Antimony, etc.).

✴OTHER TISSUES

✔ Usually these are taken when there is no way to collect fluids due to decomposition, charring or advanced mutilation.
✔ Liver-50-100g away from portal tract with total weight of liver.
✔ Brain, Spleen, Muscle 50-100g
✔ In cases of heavy metal poisoning scalp or pubic hair and bone piece can be subjected for analysis.
✔ Commonly saturated solution of NaCl, alcohol, thymol remains the common preservative.

✴Specimens For Biochemistry

✅ Vitreous humour should be taken with wide bore needle in to a syringe.
✅ Eye should be filled with water thereafter for cosmetic reasons.
✅ Potassium and other electrolytes, sugar (Glucose), urea and creatinine can be done using vitreous.
✅ Cerebrospinal fluid can also be used for this purpose.

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Collection, Preservation and Examination of Biological Samples
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