Summary of Lecture for the Day

The field of clinical and laboratory science encompasses a broad range of topics essential for
understanding diagnostic testing, patient management, and laboratory procedures. Proper sample
labeling is a foundational aspect, requiring the inclusion of basic information like age, gender,
and date to ensure sample traceability and avoid confusion in patient data. Electrophoresis, a
critical analytical technique, separates charged solutes under an electric field, which is widely
used in DNA and protein studies, providing insights into genetic material and protein
composition.

In blood sample collection, the application of a tourniquet must be managed carefully, as

prolonged application can cause falsely elevated or decreased levels of certain analytes, such as
calcium. For venipuncture, the cubital vein or median cubital is a preferred site due to ease of
access and lower risk of complications compared to other sites like inflamed or oedematous
areas. The Beer-Lambert Law plays a significant role in spectrophotometry, as it describes the
direct proportionality of a substance's absorbance to its concentration, enabling precise
quantitative analyses.

For glucose screening, Clinistix strips are commonly used in detecting glycosuria, especially in
diabetic patients. Blood levels of certain electrolytes like calcium and magnesium can be
reduced by factors like the use of anticoagulants, which may alter the specimen composition.
Reference ranges in laboratory testing are affected by physiological factors like age, posture,
Race or colour of the skin and not affected by the autoanalyzer used. Reference ranges ensure
that test results are evaluated in the context of expected normal values, which can vary across
different populations.

Renal function testing is another critical area, with initial evaluations often involving urine
analysis and blood creatinine measurements. Creatinine clearance, for example, is a
commonly used metric to evaluate kidney function, reflecting how well the kidneys are filtering
waste. Routine urinalysis includes measurements of specific gravity, pH, and physical
appearance, while factors like odor are generally not considered. In urinalysis, crystals can form
due to infection, inflammation, or kidney stones but are rarely associated with viral infections
like hepatitis B, C, A, E, etc.

Neonatal jaundice, specifically kernicterus, results from unconjugated bilirubin crossing the
blood-brain barrier, potentially causing severe neurological damage. This buildup of bilirubin
leads to a yellowish skin coloration known as jaundice or icterus. Diabetes, a common
metabolic disorder, frequently leads to complications like cardiovascular disease, highlighting
the importance of early diagnosis and management. Common symptoms include excessive
thirst, frequent urination, and weight loss, which can indicate the need for further glucose
tolerance testing.

Sample handling also requires attention to avoid errors. For instance, contamination with
EDTA can artificially elevate potassium and decrease calcium levels in a blood sample. When
performing blood collection, standing for prolonged periods before sampling can alter analyte
concentrations, such as decreasing the concentration of serum cholesterol as well as
decreasing plasma calcium levels due to postural changes.

Hematopoiesis, or blood cell formation, takes place primarily in the bone marrow, and is
critical for generating the body’s immune and circulatory components. In the immune response,
white blood cell (WBC) counts play a major role. Leukocytosis, an elevated WBC count, often
indicates infection or inflammation, while thrombocytopenia can suggest immune deficiencies
or bone marrow disorders. Platelets, though not cells themselves, are vital for clotting, with low
counts potentially indicating bleeding disorders.

In hematology, the Romanowsky stain is extensively used for differential WBC counts and
identifying abnormalities. This staining method, which uses Giemsa and methanol as a fixative,
is a staple in identifying specific cellular components in blood smears. Other examples of
Romanowsky stains include Wreight, Leishman, Field stain. Coagulase testing is another
useful diagnostic method, distinguishing Staphylococcus aureus from other species, aiding in
infection control and antibiotic selection. Catalase test is useful in differentiating
Staphylococcus species from Streptococcus species. Staphylococcus aureus is both catalase
and coagulase positive.
Microbiology also plays a critical role in diagnostics. In bacterial cultures, specific media like
Lowenstein-Jensen are used to isolate Mycobacterium tuberculosis, while MacConkey agar
differentiates lactose-fermenting bacteria like Escherichia coli by producing pink colonies.
CLED agar differentiates lactose-fermenting bacteria like Escherichia coli by producing
yellow colonies The Widal test, an immunological assay, detects antibodies against Salmonella
in suspected typhoid cases. Isolation techniques such as dilution are essential for obtaining
single bacterial colonies from mixed cultures, ensuring pure samples for accurate testing.

Fungi are another group of organisms commonly encountered in laboratory diagnostics,

especially those transmitted by spore inhalation and mostly cultured on Sabouraud Dextrose
Agar media. Fungal spores can cause respiratory infections, highlighting the need for careful
handling in labs. Bloodborne pathogens like Hepatitis A are often transmitted via the fecal-oral
route, underscoring the importance of proper hygiene in both laboratory and clinical settings.
Parasitology also involves the identification of intestinal parasites, such as Balantidium coli in
stool samples or Schistosoma haematobium ova in mid-day terminal urine collections.

Urine analysis further assists in diagnosing metabolic conditions. For example, hematuria, the
presence of RBCs in urine, may indicate urinary tract infections or kidney disease. Factors like
time at room temperature can affect urine pH, typically increasing due to bacterial activity.
Proper labeling, including patient identifiers like name and address, is essential for specimen
handling, ensuring accurate tracking and processing.

In pathology, clearing agents are used in tissue preparation for microscopy, requiring specific
properties like a refractive index close to that of tissue. Impaired fasting glucose, an early
indicator of diabetes, is defined by fasting glucose levels between 6.1 and 7.0 mmol/L. In
contrast, hypoglycemia may arise from insulin-secreting tumors or severe liver disease.
Platelets are essential for clotting and wound healing, whereas eosinophils, a type of white
blood cell, increase in allergic responses and parasitic infections.

In addition to routine tests, hematology includes methods for identifying hemoglobin variants,
such as sickling tests and electrophoresis for hemoglobin typing. Hemoglobin electrophoresis
is particularly useful in detecting genetic variants like HbS in sickle cell disease, using a power
source, hemolysate, and specific buffer solutions to separate hemoglobin types. Proper storage
and integrity of donor blood bags are essential, as any punctures or contamination may
compromise safety. You cannot open and seal the entire blood bag again because of
contamination.

Microbiological methods often involve antibiotic susceptibility testing, where the minimum
inhibitory concentration (MIC) of an antibiotic is determined to assess its efficacy against
bacteria. Blood cultures require a 1:10 blood-to-broth ratio to minimize the antibacterial effects
of serum, crucial in detecting bloodstream infections. Microscopy is also essential in these
assessments, where high-power fields (40x objectives) allow detailed examination of samples,
and illumination issues are addressed by adjusting lamp voltage or applying immersion oil.

Histology techniques like H&E staining involve eosin, a xanthene dye, which stains
cytoplasmic components pink, while hematoxylin stains nuclei blue, creating contrast that aids
in tissue examination. In metabolic testing, enzymes such as G6PD (Glucose-6-Phosphate
Dehydrogenase) are evaluated for red blood cell stability, highlighting their importance in
preventing hemolysis under oxidative stress.

These notes provide a structured overview of clinical laboratory concepts and diagnostic tools,
spanning hematology, microbiology, pathology, and metabolic testing. By integrating proper
sample handling, accurate test interpretation, and specialized techniques, laboratory
professionals play a pivotal role in patient care, guiding diagnosis, treatment, and disease
prevention.