Postmortem biochemistry is usually performed by the hospital autopsy pathologist, but it can be useful in a forensic setting.
The pathologist should be aware of the value and limitations of postmortem biochemistry because he will inevitably encounter a number of cases that require investigation into the decedent’s metabolic state.
3. Postmortem biochemistry is usually performed by the hospital
autopsy pathologist, but it can be useful in a forensic setting.
The pathologist should be aware of the value and limitations of
postmortem biochemistry because he will inevitably encounter
a number of cases that require investigation into the
decedent’s metabolic state.
Most of the previous studies were performed by comparing
premortem and postmortem fluids to show which components
remain relatively constant, which undergo predictable change,
and which are too altered to be of diagnostic use.
4. Carbohydrates and Related Metabolites.
Electrolytes and Trace Elements.
Nitrogenous Compounds.
Cholesterol and Other Lipids.
Proteins.
Bile Pigments and Other Indicators of Hepatic Function.
Hormones.
5. Carbohydrate
s and
Related
Metabolites.
Electrolytes
1.Glucose.
and Trace
Elements.
Nitrogenous 2.Ketones.
Compounds.
Cholesterol
and Other
Lipids.
3.Lactic Acid.
Proteins.
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
6. Carbohydrate 1.Glucose.
s and
Related Hypoglycemia: (it is a normal postmortem event)
Metabolites.
Electrolytes
Postmortem Decrease & Possible Value:
and Trace
Elements.
1. Due to continuous consumption of glucose by surviving
Nitrogenous cells postmortem, blood glucose levels decrease rapidly.
Compounds.
2. Its level can decrease to ZERO after few hours.
Cholesterol
and Other
3. A low glucose level in blood from the right atrium and a
Lipids.
positive test for ketones MAY support starvation in the
Proteins.
setting of abuse or neglect.
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
7. Carbohydrate 1.Glucose.
s and
Related Hyperglycemia: (a level more than 200 mg/dL)
Metabolites.
Electrolytes
and Trace
Limitations concerning sampling & Interpretation:
Elements.
1. Sampling of vitreous fluid from the centre of both eyes.
Nitrogenous
Compounds. 2. It is preferred to be sampled as soon as possible after arrival
Cholesterol at the morgue (loss of vitreous humor with low temp.).
and Other
Lipids.
3. Immediate bedside analysis using a blood gas instrument.
Proteins. 4. Standardized sampling containers must be used.
Bile Pigments
5. This level only indicates that the decedent had uncontrolled
and Other
Indicators of
diabetes.
Hepatic
Function.
Hormones.
8. Carbohydrate 1.Glucose.
s and
Related Hyperglycemia: (a level more than 200 mg/dL)
Metabolites.
Electrolytes
and Trace
Difficult interpretation & False Positive Results:
Elements.
1. Death from asphyxia, cerebral hemorrhage, congestive heart
Nitrogenous failure, electrocution, or terminal cardiopulmonary resuscitation
Compounds.
may increase postmortem peripheral vascular glucose.
Cholesterol
So, other causes of violence must be excluded by autopsy.
and Other
Lipids.
2. Other investigations must be done as well: (i) glycosuria,
Proteins. (ii) ketonuria, or (iii) elevated serum acetone level,
Bile Pigments and (iv) blood level of glycosylated hemoglobin and
and Other
(v) glycosylated fructosamine to confirm diabetic ketoacidosis.
Indicators of
Hepatic
Function.
Hormones.
9. Carbohydrate 2. Ketones & Lactic Acid.
s and
Related Total ketone bodies (acetone, acetoacetate, and b-
Metabolites. hydroxybutyrate): can be measured in PM blood, vitreous,
pericardial fluid, and urine
Electrolytes
and Trace
interpretation of Results:
Elements.
Nitrogenous 1. Serum lactic acid increases rapidly after death, and antemortem
Compounds.
levels are increased 20 times and 50 to 70 times at 1 and 24
Cholesterol hours, respectively.
and Other
Lipids. 2. Vitreous humor lactic acid increases from its initial values of 80
Proteins. to 160 mg/dL to 210 to 260 mg/dL 20 hours after death.
Bile Pigments 3. Its value allow a quick determination of Possible ketoacidosis.
and Other
Indicators of
Hepatic
Function.
Hormones.
10. Carbohydrate
s and
Related 1.Sodium, Chloride, and Potassium.
Metabolites.
Electrolytes
2. Carbon Dioxide Content.
and Trace
Elements.
Nitrogenous
3. Calcium, Magnesium, Phosphorus,
Compounds.
Cholesterol
and Sulfur.
and Other
Lipids.
4. Trace Elements.
Proteins.
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
11. Carbohydrate
s and
1.Sodium, Chloride, and Potassium.
Related
Their PM blood concentration do not accurately reflect AM levels
Metabolites.
because of variable instability after death.
Electrolytes
and Trace
Elements.
interpretation of Results:
Nitrogenous
Compounds. 1. Vitreous sodium (150 – 190 mEq/L) concentration remain
Cholesterol relatively stable in the early postmortem period.
and Other
Lipids. 2. Vitreous chloride (114 mEq/L) concentration remain almost
constant during the early 18 hours.
Proteins.
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
12. Carbohydrate
s and
1.Sodium, Chloride, and Potassium.
Related
interpretation of Results:
Metabolites.
3. The blood potassium level rises extremely rapidly after death as cell
Electrolytes
membranes lose integrity. In vitreous, PM K+ levels rise gradually (stable
and Trace
Elements. correlation phase), however, the margin of error in these calculations is
HIGH and vitreous K+ levels should not be used to estimate time of death,
Nitrogenous
due to many factors:
Compounds.
a. Possible AM electrolytes’ imbalance.
Cholesterol
b. Metabolic diseases.
and Other
Lipids. c. Environmental temperature (inappropriate conservation - lower in
cold weather).
Proteins.
d. The K+ rise is faster in infants> adults.
Bile Pigments e. Inappropriate sampling (near retinal lining) false results.
and Other
f. Further clinical researches and case-studies are in process.
Indicators of
Hepatic
Function.
Hormones.
13. Carbohydrate 2. Carbon Dioxide.
s and
Related ML Significance:
Metabolites. Postmortem vitreous carbon dioxide content averages
15 mEq/L (range 4 to 27 mEq/L) and remains relatively stable for at
Electrolytes
least 15 hours after death.
and Trace
Elements.
Nitrogenous 3. Calcium, Magnesium, Phosphorus, and Sulfur.
Compounds.
Cholesterol
ML significance: of little use
and Other The serum Ca++ remains briefly stable and then rises slowly. Initial
Lipids.
vitreous calcium levels range from 6 to 8 mg/dL (1.5 to 2 mmol/L),
and the values rise very slowly until decomposition ensues.
Proteins. Mg++in vitreous humor rise slowly but erratically after death.
Inorganic and organic phosphorus levels increase quickly after
Bile Pigments death.
and Other Sulfate levels are stable during the initial PM period.
Indicators of
Hepatic
Function.
Hormones.
14. Carbohydrate
s and
Related
Metabolites.
Electrolytes
and Trace
1. Urea Nitrogen and Creatinine.
Elements.
Nitrogenous
Compounds.
2. Other Nitrogenous Compounds.
Cholesterol
and Other
Lipids.
Proteins.
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
15. Carbohydrate 1. Urea Nitrogen & Creatinine.
s and
Related ML significance:
Metabolites. Postmortem Urea nitrogen & creatinine are perhaps the most stable
blood constituent following death as it approximates premortem
Electrolytes
levels, even after moderate decomposition.
and Trace
Elements.
Nitrogenous
Compounds.
Cholesterol
and Other
Lipids.
Proteins.
These patterns can indicate child neglect, homicide, septicemia,
Bile Pigments
SIDS, alcoholism, or prolonged diuretic therapy.
and Other
Creatinine is a valid postmortem marker of nitrogen retention and
Indicators of renal function.
Hepatic
Function.
Hormones.
16. Carbohydrate 2. Other Nitrogenous Compounds.
s and
concentrations of ammonia, amino acids, glutamine,
Related
creatine, and oxypurines (uric acid, xanthine, and hypoxanthine)
Metabolites.
Electrolytes
and Trace ML Significance:
Elements.
All these compounds increase after death.
Nitrogenous
PM ammonia levels in vitreous humor increase linearly – during the
Compounds.
first 24 hours.
Cholesterol
Although relatively stable after death, uric acid levels are higher in
and Other
Lipids. blood samples from the right side of the heart than from left heart or
periphery. Postmortem hyperuricemia may also be elevated after
Proteins.
death caused by asphyxiation or drowning, but further studies of this
Bile Pigments
and Other
finding are required.
Indicators of
Hepatic
Function.
Hormones.
17. Carbohydrate
s and
ML Significance:
Related
Metabolites.
Postmortem serum total cholesterol used to identify familial
Electrolytes
hypercholesterolemia.
and Trace
Elements.
Correlation of PM serum lipid levels with AM state is difficult:
1. The decedent may not have been in a fasting state at the
Nitrogenous
Compounds. time of death.
2. Familial hyperlipoproteinemias have been identified from
Cholesterol
and Other postmortem studies.
Lipids. 3. Elevated levels of postmortem lipids in serum and other
Proteins. fluids have been associated with the presence of coronary
Bile Pigments heart disease and sudden cardiac death.
and Other
Indicators of
Hepatic
Function.
Hormones.
18. ML Significance:
Carbohydrate
s and
Related Albumin/Globulin ratio: PM studies show that the values for total
Metabolites. proteins and ratio are similar to those of AM specimens.
Electrolytes
and Trace 1. Provided that there is minimal hemolysis, serum
Elements. electrophoresis has been useful in the postmortem diagnosis
Nitrogenous of agammaglobulinemia, monoclonal gammopathy, and
Compounds.
hemoglobinopathies .
Cholesterol
and Other 2. Total immunoglobulin E (IgE) is elevated in some cases of
Lipids. fatal asthma.
Proteins.
3. Specific IgE antibodies in postmortem serum may help
Bile Pigments
and Other
corroborate the diagnosis of anaphylaxis following insect
Indicators of stings or ingestion of allergenic food.
Hepatic
Function.
Hormones.
19. ML Significance:
Carbohydrate
s and
Related
Metabolites. C-reactive protein: PM Postmortem measurement of in the blood or
Electrolytes liver (if blood is not available):
and Trace
1. If marked elevation and in case of doubt of minimal injury: it
Elements.
may indicate a natural mode of death in decedents.
Nitrogenous
2. In those with obvious trauma, it suggests a vital reaction.
Compounds.
Cholesterol
CRP levels were independent of the post-mortem interval.
and Other
Lipids. CRP is stable for 1 month PM (easy, viable, inexpensive).
Proteins.
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
20. ML Significance:
Carbohydrate
s and
Related
Enzymes:
Metabolites.
1. Elevated levels of creatine kinase, lactic dehydrogenase, and
Electrolytes
their isozymes in pericardial fluid and serum have been
correlated with myocardial injury related to trauma or the
and Trace
early stages of myocardial infarcts.
Elements.
Nitrogenous 2. Myosin concentration was a better indicator of widespread
Compounds. cardiac muscle damage.
Cholesterol 3. Postmortem pericardial levels of cardiac troponin I greater
and Other than 40 ng/mL (better combined with troponin T) correlated
Lipids. closely with pericardial concentrations of myoglobin, with
elevated troponin levels supporting a diagnosis of cardiac
Proteins. injury (the highest level was in acute MI).
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
21. ML Significance:
Carbohydrate
s and
Related
Enzymes:
Metabolites.
4. Mast cell tryptase (combined assay for a- and b-tryptase) has
Electrolytes
been used to detect anaphylactic reactions (NOT-specific
and Trace
elevated in other conditions, including coronary artery
Elements. thrombosis, heroin injection, sudden infant death syndrome,
amniotic fluid embolism, and asphyxia).
Nitrogenous
Compounds.
To increase accuracy, MAY be combined with:
Cholesterol
(1) accurate medical history (particularly atopic disposition of
the decedent and temporal relationship of possible allergen
and Other
exposure and death).
Lipids.
(2) findings at autopsy, total IgE levels, and,
Proteins.
(3) if possible, analysis of relevant IgE antibodies.
(4) A peripheral blood is better (heart blood contains more
Bile Pigments elevated levels of tryptases).
and Other
Indicators of
Hepatic
Function.
Hormones.
22. ML Significance:
Carbohydrate
s and
Serum Bilirubin : increase slowly after death but allow determination
Related
of the extent of antemortem jaundice; however, minimal elevations
Metabolites. of postmortem bilirubin are difficult to interpret.
Electrolytes Urobilinogen remains stable in the urine but diffuses from blood to
and Trace CSF whenever the blood level is high.
Elements.
MILD liver dysfunction cannot be readily assessed using
Nitrogenous postmortem chemical analysis because the enzymes used to
Compounds.
assess liver function become elevated after death, BUT, total
cholesterol + low serum protein levels with inversion of the
Cholesterol albumin/globulin ratio + high serum bilirubin level + and the
and Other presence of abnormal levels of bile and urobilinogen in the urine
Lipids.
CONFIRM SEVERE liver damage.
Elevation of glutamine level in the postmortem CSF samples
Proteins.
CORRELATES with Hepatic Coma.
Bile Pigments
and Other
Indicators of
Hepatic
Function.
Hormones.
23. ML significance:
Carbohydrate
s and Serum cortisol, parathormone, chorionic gonadotropin, thyroid-
Related stimulating hormone, and luteinizing hormone concentrations remain
Metabolites. stable in the early postmortem period.
Insulin Poisoning (suicide and homicide): Serum insulin is extremely
Electrolytes difficult to measure accurately because it degrades rapidly at room
and Trace temperature.
Elements. Diagnosis can be made as follows:
1. Peripheral blood samples should be collected in tubes containing
Nitrogenous
sodium fluoride or ethylenediaminetetraacetic acid (EDTA).
Compounds.
2. Serum should be separated from red blood cells as soon as possible
Cholesterol
3. Samples should be refrigerated or, preferably, frozen.
and Other
4. Elevated PM blood INSULIN.
Lipids.
5. Low blood C Peptide (a diagnosis of exogenous insulin overdose).
Proteins. 6. In postmortem blood, C peptide is more stable than insulin, although
Bile Pigments collections still require special handling: collection in heparinized
and Other tubes, separation of plasma, and, without delay, storage of the
Indicators of serum sample in a freezer.
Hepatic
Function.
Hormones.
24. Interpretation of biochemical results must be done with great caution
& on an individual case by case basis.
High selection of suspected and criminal cases is a necessity, rather
than wasting efforts, time and costs in revealing cause of death in
normal natural deaths.
Re-evaluation and unifying toxicological and histopathological
investigations through providing experienced professionals in these
fields, extensive scientific cooperation including immunostaning
studies for histopathology and sharing thoughts and plans for better
achievement with these departments.
Group meeting and workshops are needed with the related
laboratories to study further cooperation, feasibility studies, and cost
effectiveness of these sophisticated investigations in specific kinds of
medicolegal cases.