Lecture 5 - Clinical instrumentation

Question 1

Types of biomedical scientists: INFECTION SCIENCES

Answer 1

• medical microbiology - identification of micro-organisms causing disease and their antibiotic treatment
• virology - identification of viruses, associated diseases and monitoring the effectiveness of vaccines.

Question 2

Types of biomedical scientists: BLOOD SCIENCES

Answer 2

• clinical chemistry - analysis of body fluids and toxicology studies
• transfusion science - determination of donor/recipient blood compatibility, ensuring blood banks are sufficient
• haematology - form and functions of blood and related diseases
• immunology - understanding the immune system and its role in combating disease.

Question 3

Types of biomedical scientists: CELLULAR SCIENCES

Answer 3

• histopathology - microscopic examination of diseased tissue samples
• cytology - best known for cervical smear screening, but also covers other cellular analysis.

Question 4

Types of biomedical scientists: GENETIC & MOLECULAR PATHOLOGY

Answer 4

• genetics - study of genes and hereditary variations in genes
• molecular pathology - study and diagnosis of disease through examination of tissues and fluids at molecular level.

Question 5

Waht is Clinical chemistry?

Answer 5

• Clinical chemistry refers to the biochemical analysis of body fluids.
• It uses chemical reactions to determine the levels of various chemical compounds in bodily fluids.
• Several simple chemical tests are used to detect and quantify different compounds in blood and urine, the most commonly tested specimens in clinical chemistry.

Question 6

State some techniques used in clinical chemistry

Answer 6

Techniques such as:

• Spectrophotometry
• Immunoassays
• Electrophoresis

are also used in clinical chemistry to measure the concentration of substances such as:

Glucose, lipids, enzymes, electrolytes, hormones, proteins, and other metabolic products present in human blood and urine.

Question 7

Specimens tested in clinical analysis: SERUM

Answer 7

• Most common specimen tested;
• Obtained by centrifugation of coagulated blood;
• Doesn’t contain blood cells or clotting factors, but contains electrolytes, hormones, antigens, antibodies, and other substances such as drugs, microbes, or proteins.

Question 8

Specimens tested in clinical analysis: Plasma

Answer 8

• Obtained by centrifugation of uncoagulated blood;
• Contains blood cells, clotting factors, glucose, electrolytes (such as sodium, magnesium, calcium, chloride), hormones, and proteins (such as albumins, fibrinogen, and globulins).

Question 9

Specimens tested in clinical analysis: Urine

Answer 9

The collection container usually contains a preservative.

Question 10

Specimens tested in clinical analysis: CEREBROSPINAL FLUID (CSF):

Answer 10

• Is a clear fluid present in the brain and spine which is largely similar to blood plasma, though it differs as it doesn’t contain any protein.
• Analysed to rule out meningitis.

Question 11

What are the key parameters of carbohydrates tested and their significance?

Answer 11

CARBOHYDRATES -

Glucose levels indicate the body’s efficiency in metabolizing glucose. Fasting and random glucose levels in blood help in the diagnosis of endocrinological disorders such as hypoglycemia (low blood sugar) and diabetes.

Question 12

What are the key parameters of lipids tested and their significance?

Answer 12

present in different forms as body fat, as part of cell membranes, and as sterols such as cholesterol.

-Diagnosis of liver and heart disease in humans.

Question 13

What are the risk factors associated with high levels of lipids in blood?

Answer 13

present in different forms as body fat, as part of cell membranes, and as sterols such as cholesterol.

-Diagnosis of liver and heart disease in humans.

Question 14

What are the key parameters of enzymes tested and their significance?

Answer 14

ENZYMES - Measuring the levels of enzymes released by organs into the blood can indicate problems with a particular organ.

Examples:

1) Creatine kinase in the body indicate heart or skeletal muscle damage
2) Alanine aminotransferase or aspartate aminotransferase levels indicate liver disorders
3) Amylase and lipase signal pancreas inflammation or pancreatic carcinoma.

Question 15

What are the key parameters of hormones tested and their significance?

Answer 15

Measuring levels of hormones can help determine if the corresponding glands are functioning correctly or are hyperactive/ hypoactive.

Examples:

1) Cortisol is a hormone secreted by the adrenal glands;
2) Thyroxine (T4) and thyroid stimulating hormone (TSH) are secreted by the thyroid gland;
3) Follicle stimulating hormone (FSH) and growth hormones are secreted by the pituitary gland.

Question 16

What are the key parameters of proteins tested and their significance?

Answer 16

The concentration of proteins in the body can be indicative of nutritional and metabolic disorders and some forms of cancer.

Example:

1) Total protein and albumin linked to liver or kidney disease;
2) Globulin levels and the ratio of albumin to globulin can help detect infection, inflammation, autoimmune disease, and some forms of blood cancer.

Question 17

What are the key parameters of electrolytes tested and their significance?

Answer 17

The levels of various electrolytes such as Na, Cl, K, Ca, bicarbonate, phosphorus, and Mg in the body can help diagnose some kidney and metabolic disorders.

Question 18

What are the key parameters of metabolites tested and their significance?

Answer 18

Levels of urea, nitrogen and creatinine in the blood are indicators of kidney function. Similarly, uric acid levels can signal kidney disease, gout, and damage to other tissues.

Question 19

Chemistry analysers: Cobas e501

Answer 19

• Up to 1000 tests/hr;
• fully automated;
• performs over 110 measurements of proteins, enzymes, substrates and electrolytes, direct anti-globulin tests (DATs), and therapeutic drug monitoring (TDMs).

Question 20

Chemistry analysers: Cobas e601

Answer 20

• 175 tests/hr;
• fully automated;
• immunoassay tests using Electro ChemiLuminescence (ECL) technology.

Question 21

Chemistry analysers: Cobas 6000 modular analyser:

Answer 21

• 15 million tests per annum
• 220 parameters consolidated on one system
• Customised to fit the labs needs
• Core module + Cobas e501 + Cobas e601.

Question 22

Cobas6000 analyser series- clinical chemistry menu

Answer 22

Question 23

Other methods –dipstick tests

Describe Urinanalysis (US)

What is it used for?

Answer 23

• Used as a screening and/or diagnostic tool to detect substances or cellular material in the urine associated with metabolic disorders, renal dysfunction or urinary tract infections (UTI).
• Often, substances such as protein or glucose will begin to appear in the urine before patients are aware that they may have a problem.

Question 24

How can urine be assesssed?

Answer 24

Urine may be assessed both at the bedside (dipstick) and in the laboratory (microscopy, culture, sensitivity and urinary electrolytes).

Urine for laboratory analysis must be transferred quickly and at the correct temperature otherwise breeding ground for contaminants.

Question 25

What is SPECIFIC GRAVITY (1.002 – 1.035) of urine?

Answer 25

A measure of the amount of solutes dissolved in urine as compared to water (1.000).

It measures the ability of the kidney to concentrate or dilute the urine and is directly proportional to urine osmolality (solute concentration).

Question 26

What does a specific gravity of <1.005 mean?

Answer 26

• Inability to concentrate urine or excessive hydration (volume resuscitation with IV fluids)
• Nephrogenic diabetes insipidus, acute glomerulonephritis, pyelonephritis, acute tubular necrosis
• If specific gravity is not > 1.022 after a 12 hour period without food or water →renal concentrating ability is impaired and the patient either has generalized renal impairment or nephrogenic diabetes insipidus.
• Falsely low specific gravity can be associated with alkaline urine

Question 27

What does a specific gravity of 1.010 mean?

Answer 27

• The glomerular filtrate in Bowman’s space ranges from 1.007 to 1.010. Any measurement below this range indicates hydration and any measurement above it indicates relative dehydration.
• In end stage renal disease, specific gravity tends towards 1.010.
• Chronic Renal Failure (CRF), Chronic glomerulonephritis (GN)

Question 28

What does a specific gravity of >1.035 mean?

Answer 28

• Increased specific gravity indicates a concentrated urine with a large volume of dissolved solutes
• Dehydration (fever, vomiting, diarrhea), adrenal insufficiency, pre-renal failure, liver failure, nephrotic syndrome
• Elevation in specific gravity also occurs with glycosuria (e.g. diabetes mellitus), proteinuria or urine contamination.

Question 29

What does a urine pH (4.5-8.0) indicate?

Answer 29

The kidneys play an important role in acid-base regulation within the body to maintain a normal urinary pH range between 5.5 – 6.5, but it may vary from as low as 4.5 to as high as 8.0.

Control of pH is important in the management of several diseases, including bacteriuria, renal calculi, and drug therapy.

Question 30

What does a high urine pH indicate?

Answer 30

High Urinary pH = Alkali Urine

• Vegetarian diet, low carbohydrate diet or ingestion of citrus fruit (although citrus fruits are acidic – the digestion process leaves an alkali ash)
• Renal tubular acidosis, Fanconi syndrome
• Urinary tract infections (bacteriuria with urea splitting organisms)

Question 31

What does a low urine pH indicate?

Answer 31

Low Urinary pH= Acidic urine

• High protein diet or fruits such as cranberries
• Diabetes mellitus, starvation, diarrhoea, malabsorption
• Phenylketonuria, alkaptonuria, renal tuberculosis

Question 32

What does Leucocytes (White cell count-WCC) determine?

Answer 32

• Determines the presence of whole or lysed white cells in the urine (pyuria) by detecting leucocyte esterase activity.
• A positive leucocyte esterase test correlates well with pyuria. However, the diagnosis may be missed in up to 20% of cases if a negative urinalysis dipstick is used to exclude UTI.

Question 33

What are the causes of false positves/negatives of WCCs?

Answer 33

False positive: Contaminated specimen, trichomonas vaginalis, drugs or foods that colour the urine red

False negative: Recent antibiotic therapy (especially gentamicin, tetracycline and cephalosporins), glycosuria, proteinuria, high specific gravity. Low bacteria count UTI (especially in women)