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Medical Laboratory Technology: Volume III
Abbreviation Expanded Version
GTT
GU
H AV
Hb
HEPA
HBV
hcg
–
НСО
3
Hct
HCV
HDL chol
Glucose tolerance test
Genitourinary
Hepatitis A virus
Haemoglobin
High eciency particulate air
Hepatitis В virus
Human chorionic gonadotropin
Bicarbonate
Haematocrit
Hepatitis С virus
High density lipoprotein
cholesterol
HDN
Haemolytic disease of the
newborn
H & H
HIV
Haemoglobin and haematocrit
Human immunodeciency
virus
HLA
ICU
Ig
IgG
IgM
IM
ITP
Human leukocyte antigen
Intensive care unit
Immunoglobulin
Immunoglobulin G
Immunoglobulin M
Infectious mononucleosis
Idiopathic thrombocytopenic
purpura
IU
IV, i.v.
Kg
L
LD, LDH
LDL Chol
International unit
Intravenous
Kilogram
Litre
Lactate dehydrogenase
Low density lipoprotein
cholesterol
LPF
m
M
MCH
MCHC
Low power eld
Meter
Molar
Mean cell haemoglobin
Mean cell haemoglobin
concentration
MCV
μg
Mean cell volume
Microgram
Abbreviation Expanded Version
μL
μmοl
mEq
mg
MI
mIU
mL
MLT
mm
mmol
mol
MT
nm
OD
OGTT
OSHA
Microlitre
Micromole
Milliequivalent
Milligram
Myocardial infarction
Milli International Unit
Milliter
Medical laboratory technology
Millimetre
Millimole
Mole
Medical technologist
Nanometre
Optical density
Oral glucose tolerance test
Occupational safety and health
admininstration
Pa
PCV
рH
PMN
РОСТ
ppm
PRC
PT
QA
QC
q.s.
RA
RBC
RF
RhlG
RIA
RNA
RPM
RPR
sed rate
SGOT
Pascal (unit of pressure)
Packed cell volume
Hydrogen ion concentration
Polymorphonuclear neutrophil
Point-of-care testing
Parts per million
Packed red cells
Prothrombin time
Quality assessment
Quality control
Quantity sucient
Rheumatoid arthritis
Red blood cells
Rheumatoid factors
Rh immune globulin
Radioimmunoassay
Ribonucleic acid
Revolution per minute
Rapid plasma reagin
Erythrocyte sedimentation rate
Serum glutamic oxaloacetic
transaminase
xxi
Commonly Used Abbreviations in Medical Laboratories
Abbreviation Expanded Version
SGPT
Serum glutamic-pyruvic
transaminase
SI
sp.gr.
staph
Stat
STD
STI
strep
STS
TIBC
TLC
UA
UP
International unit
Specic gravity
Staphylococcus
Immediately
Sexually transmitted disease
Sexually transmitted infection
Streptococcus
Serological test for syphilis
Total iron binding capcity
Total leukocyte count
Thin layer chromatography
Urinalysis uric acid
Universal precaution
Abbreviation Expanded Version
UTI
UV
VD
VDRL
Urinary tract infection
Ultraviolet
Venereal disease
Venereal Disease Research
Laboratory
VLDL
vWF
W В С
WHMIS
Very low density lipoproteins
Von Willebrand factor
White blood cell
Workplace Hazardous
Materials Information
WHO
XDP
>
<
World Health Organization
Fibrin degradation product
More than
Less than
xxi
Section 7
CLINICAL
BIOCHEMISTRY
Chapter 29: Biochemical Processes of the Body Under Normal and Pathogenic
Conditions
Chapter 30: Specimen Collection and Processing for Biochemical Analyses
Chapter 31: Techniques of Analytical Chemistry
Chapter 32: Automation in Clinical Biochemistry .
Chapter 33: Routine Biochemical Test Procedures
Chapter 34: Biochemical Test Proles
Chapter 35: Therapeutic Drug Monitoring and Clinical Toxicology
899
Biochemical Processes of the Body Under Normal and Pathogenic Conditions
Vissagan Gopalakrishnan and Piyali Basu
Chapter Outline
• Normal and Abnormal Biochemical Processes of the Body
• Basic Physiology and Biochemistry of the Body
• Interrelated Metabolic Processes of the Body
• Functions of Various Organs
• Biochemical Changes in the Body Under Pathologic Conditions
• Basic Clinical Biochemistry
▪ Chemistry Proles
▪ Types of Specimens for Chemical Analyses
▪ Units of Measure in Clinical Chemistry
▪ Reference (Normal) Ranges
• Diagnostic Biochemical Proles
• Review Questions
29
Normal aNd abNormal biochemical Processes of the body
The clinical biochemistry laboratory analyses the chemical constituents of various body
uids, notably serum (or plasma), urine and spinal uid. Most of these analyses reect the
biochemical malfunction of various key organs of the body such as the liver, heart, kidney,
brain and pancreas and the endocrine system. Thus it becomes imperative for any beginner to
understand the basic biochemical setup of the body and the role of various organs to maintain
homeostasis (chemical balance) in the body. This understanding helps in the diagnosis of a
diseased state on the basis of specic biochemical changes.
These specic biochemical changes are called biomarkers, and they are oen used as an
ecient and standard means to access a certain adverse condition and compare it to other
similar cases. For example, high levels of Troponin I, a muscle protein, in blood is strongly
indicative of a myocardial infarction (MI), also known as heart aack. From a clinical
perspective, the use of these biomarkers can allow for a faster diagnosis. Instead of running
expensive, and sometimes invasive, diagnostic procedures, physicians can instead look for
specic triggers that preclude a certain condition.
901
902
The practice of medicine popular in media today tends to xate on acute cases on a specic
organ/tissue; however, most people suer from more chronic conditions. These chronic
malfunctions are more dicult to identify and comprehend. However, an understanding of
normal and abnormal biochemical processes of the body allows a diagnostician and physician
to provide more holistic care and beer medicine as a result.
Medical Laboratory Technology: Volume 3
basic Physiology aNd biochemistry of the body
The human body is an incredible machine that utilizes ‘fuel’ to run a broad range of activities,
from movement of extremities to reproduction. It delivers this function through the
coordination of biochemical processes. The food that the body consumes (carbohydrates, fats
and proteins) acts as the source that supplies energy and in addition, participates in building
the structure of the body (anabolism).
The materials that the body consumes are classied in chemical terms as organic and
inorganic. Inorganic compounds can be salts, water, acids, and bases. These compounds (e.g.,
sodium chloride, NaCl or common salt) do not contain carbon and do not originate from
living maer. Organic compounds, however, are related to living material and have carbon
atoms as their essential constituent. The intake of organic food, water, inorganic salts and
vitamins leads to the synthesis of a variety of organic substances inside the body that play a
vital role in its sustenance. This process of creating supportive compounds within the body
is called anabolism, and is contrasted with catabolism of carbohydrates and other fuel sources.
Organic compounds are used to build body structure, supply and store energy (e.g., glycogen,
fats, etc.), regulate biochemical processes at the cellular level (e.g., enzymes), and regulate
interrelated activities of various organs (e.g., hormones). The inorganic salts control many
physical processes of the body such as osmotic pressure. They typically enter into structures
of various organic compounds and are closely related to dierent physiological functions of
the body (Figure 29.1). Water metabolism and pH (a measurement of acidity and alkalinity)
also play a signicant role in numerous biochemical processes. These will be discussed in
subsequent sections.
The basic physiological functions of the body are carried out by a few organs (Figure
29.2). These can be broadly divided into the digestive system, circulatory system, respiratory
system, excretory system and reproductive system. The digestive system breaks down
complex organic molecules into simpler molecules, which are then absorbed into the blood.
The excretory system helps to eliminate the materials that the body cannot absorb. The heart
is a mechanical pump that maintains the constant movement of blood throughout the body.
The lungs are utilized for gas exchange, whereby carbon dioxide is released as oxygen is
inhaled. The kidneys and liver helps in ltering the blood. Unwanted metabolites and toxins
are rejected and the essential ones are taken back into circulation. The pancreas is used to
maintain blood sugar levels via the secretion of insulin. Figure 29.2 identies the location of
these organs in the human body.
The endocrine glands modulate many physiological processes over the long-term by
secreting chemical messengers called hormones. These chemicals can be tissue-specic and
typically act to alter systemic functions. Enzymes, on the other hand, regulate intracellular
biochemical activities. The characteristic functions of various vital organs of the body (liver,
heart, kidney, pancreas, etc.) are closely related to their enzymatic composition. Enzymes
catalyse a specic chemical reaction by reducing the activation energy required to instigate
the reaction. For example, carbonic anhydrase found in red blood cells catalyses the rapid
conversion of carbon dioxide and water to bicarbonate. It is one of the fastest enzymes in the
body and its function is critical to the transport of carbon dioxide from peripheral tissue to
the lungs. Intracellular enzymes can also be secreted into the blood stream in cases of trauma
or distress. The search for elevated levels of specic enzymes in blood sera forms the basis of
diagnostic enzymology.
The chemical structures of some of the basic organic compounds connected with the physiology of
the body are shown in Figure 29.2. These and many other organic compounds enter into the structure
of the body and govern its complex physiological functions.
Biochemical Processes of the Body Under Normal and Pathogenic Conditions
903
Figure 29.1 Some important chemical structures that form the basis of various organic compounds of the
body (R, alkyl group with varying numbers of carbon atoms).
Carbohydrates are a class of organic compounds
containing the elements carbon (C), hydrogen (H)
and oxygen (O). They form the principal source
of energy for the body. Sugars are carbohydrates,
which are classied as monosaccharides or simple
sugars, such as glucose, fructose and galactose,
disaccharides, such as maltose and sucrose, and
polysaccharides, such as starch and glycogen, which
are complex carbohydrates formed by the union of
monosaccharides. Hydrolysis is a chemical reaction
by which complex organic compounds such as starch
are broken down to simpler components (Figure
29.3). As the name implies, water molecules are
utilized in the cleavage process. Polysaccharides are
hydrolysed to sugars, proteins to amino acids, and
fats to fay acids and glycerol. Digestion of food in
the digestive tract is largely a process of hydrolysis
accomplished by various digestive enzymes that
break down carbohydrates, fats and proteins.
Proteins are organic nitrogenous compounds of the body
made of amino acids (principally), which are linked by
Figure 29.2 Location of some important
organs of the body
904
Medical Laboratory Technology: Volume 3
Figure 29.3 Chemical structures of some of the important biochemical constituents of the body: (a) Carbo-
hydrate, (b) Protein, (c) Nucleotide, and (d) Steroids.
peptide bonds (Figure 29.3). The elemental composition of proteins includes carbon, hydrogen,
oxygen and nitrogen, and occasionally sulphur, phosphorous, iron and other metals. Proteins
form the basic structural component of the body. They may act as a secondary source of
energy from the oxidation of their hydrolysed product, the amino acids. Serum proteins
include albumin and four components of globulin—alpha1, alpha2, beta and gamma. Proteins
are classied as simple or conjugated. Upon hydrolysis, the simple proteins (for example,
albumin and globulin) are reduced to amino acids. Conjugated proteins, on the other hand,
Biochemical Processes of the Body Under Normal and Pathogenic Conditions
905
produce other organic compounds along with amino acids. Some examples of conjugated
proteins are haemoglobin, nucleoprotein, phosphor-protein and lipoprotein.
Amino acids, the building blocks of protein, are formed by the amination of carboxylic
acids. The basic formula for the amino acids is NH2–CH(R)–COOH where R stands for
various organic compounds, either aliphatic or aromatic (Figure 29.3). When amino acids are
used as a source of energy by the body, the amino group (NH2) ‘s rst removed through the
process of deamination. The ammonia generated by the deamination process is converted to
urea (CO[NH2]2) in the liver through the ornithine cycle (Figure 29.4). The remaining organic
acid then enters into the Krebs cycle and is oxidized (Figure 29.9). There are about 22 amino
acids generally found in the living body, of which 10 are essential. Numerous combinations
in the amino acid sequence lead to the existence of an unlimited number of plant and animal
proteins. Amino acids can well be considered the alphabet that spells life.
Non-protein nitrogenous compounds are also important constituents of the body. These
include urea, uric acid, creatinine, bilirubin, urobilinogen and nucleic acids.
Urea is synthesized in the liver by combining ammonia with carbon dioxide (Figure 29.4).
It is eliminated through urine, which protects the body from ammonia toxicity. Uric acid
is the product of purine metabolism and is a result of nucleoprotein breakdown. Uric acid
cannot be metabolized by the body and is eliminated through the urine. Accumulation of uric
acid in the blood results in renal failure.
Figure 29.4 Process of urea synthesis (ornithine cycle)
Dehydration of creatine generates Creatinine. Creatine is associated with the anaerobic phase
of muscle contraction and energy transfer. Creatinine is maintained at a constant level in the
body and excess is eliminated through the urine.
Bilirubin is a pigmented non-protein nitrogenous compound of the body that originates
from the breakdown of haemoglobin (Figure 29.5). Haemoglobin consists of a complex
organic compound haeme (iron + protoporphyrin, a tetrapyrrole) and globin (a protein). The
degradation of haemoglobin in the reticuloendothelial cells of the spleen produces free, or
unconjugated, bilirubin (Figure 29.5). Unconjugated bilirubin is insoluble in water, and thus
cannot be transported in the blood without rst binding the serum protein albumin. Bilirubinalbumin complexes are transported to the liver, where they are conjugated with glucoronic
acid. The conjugated bilirubin is now water-soluble, and is excreted from the liver into the
duodenum via bile. In the intestine, bacterial enzymes convert bilirubin into urobilinogen.
Most of the urobilinogen is eliminated through faeces, and a portion of it is reabsorbed from
the intestine into blood circulation. The reabsorbed urobilinogen is excreted through urine or
re-excreted in bile along with the conjugated bilirubin.
Nucleic acids are another group of complex organic nitrogenous compounds. They
are primarily found in the cytoplasm and nucleus and form the physical manifestation of
genetic information. The most important nucleic acids are ribonucleic acid (RNA) and