practical enzymology

Practical clinical biochemistry

Dr. Abdulhussien Mahdi Aljebory
College of pharmacy
University of Babylon


? Clinical Biochemistry is concerned with changes in the composition of blood, and other body fluids, associated with diagnosis of disease, monitoring of therapy, and prognosis.

? Clinical Biochemistry is that discipline which applies basic biochemistry and analytical chemistry to medical diagnosis, treatment and management.

? This can involve carrying out specialist analyses; developing and implementing new techniques, and interpreting the results.
Objectives of Studying Clinical Biochemistry
? To Understand :
? the principles of the analytical techniques used in a Clinical Biochemistry Department.
? the procedures used to set-up, assess and maintain the quality of laboratory analyses.
? the physiological and pathological processes affecting biochemical investigations.
? the use of clinical biochemistry results in the diagnosis and management of common medical disorders.
Proper Sampling
• Proper blood collection tube.
• Adequate volume.
• Not haemolyzed.
• Labeled with:
• Patient name.
• Age.
• Department.
• hospital number.
• Date of specimen collection.
• Not obtained from indwelling line or catheter.
• Transported to the lab within one hour.
• The tube should be set upright in a rack and separated from the request to avoid its contamination.

How to avoid hemolysis of the sample?
• Not using too fine needle.
• Deliver the blood slowly into the tube (not through the needle).
• Anticoagulated specimens should be mixed by inverting the tube several times slowly (avoid excessive shaking).
How to take a blood sample?
Blood can be drawn by:
? a venipuncture,
? skin puncture or
? Arterial blood sampling
SAMPLING ERRORS
There are a number of errors which may contribute to success or failure of the laboratory to provide the correct answers to the clinician s questions.

? Blood sampling technique:

difficulty in obtaining a blood sample may lead to hemolysis ? release of potassium and other red cell constituents ? results for these will be falsely elevated.

? Prolonged stasis during venepuncture: plasma water diffuses into the interstitial space ? serum or plasma sample obtained will be concentrated ? proteins and protein-bound components of plasma as calcium or thyroxine will be falsely elevated.


? Insufficient specimen:

each biochemical analysis requires a certain volume of specimen.
It may be impossible to measure everything requested on a small volume specimen.

? Errors in timing:

the biggest error in the measurement of any analyte in a 24-hour urine specimen is collecting an inaccurately timed volume of urine.

? Incorrect specimen container:
- samples for glucose should collected in tube containing fluoride to inhibits glycolysis; otherwise the time taken to deliver the sample to laboratory can affect the result.

- If a sample is collected in wrong container, it should never be decanted into another tube.
For example, blood which has been exposed even briefly to EDTA (an anticoagulant used in sample containers for lipids and CBC) will have a markedly reduced calcium conc. (zero)


? Inappropriate sampling site:
blood samples for glucose request should not be taken "downstream" from an intravenous dextrose drip.
? Incorrect specimen storage:
a blood sample stored overnight before being sent to the laboratory ? falsely high potassium, phosphate and RBCs enzymes as lactate dehydrogenase because of leakage from the cells into the extracellular fluid.
Patient preparation and sample variables
Physiologic considerations:
such as cyclic changes, exercise, stress, medical conditions, gender and age.

Nutritional status: such as diet and fasting.

Smoking: nicotine increases blood glucose, by stimulating adrenaline release, this in turn converts glycogen to glucose.
Alcohol intake.
Drugs.
Formulation of Lab Requests
? Write a lab request to reach a final diagnosis for a case of acute hepatitis:
1- Viral markers
2- serum bilirubin (total& direct)
3- Serum ALT
4- Serum AST
5- Serum ALP
6- Serum GGT
Write a Lab request with the recommended laboratory investigations in a case of chronic hepatitis.
1-Viral markers
2-serum bilirubin (total& direct)
3- Serum ALT
4-Serum AST
5-Serum ALP
6-Serum GGT
7-serum albumin
8-prothrombin time

Write a Lab request with the recommended laboratory investigations in a case of diabetes mellitus.
1-fasting blood glucose
2-postprandial blood glucose
? for follow up a case of diabetes mellitus:
? Glycated Hb every 2-3 months


Write a lab request with the recommended laboratory investigations in glucose metabolism disorders

1-fasting blood glucose
2-postprandial blood glucose
3-oral glucose tolerance test
4-glycated Hb
Write a Lab request with the recommended laboratory investigations in a case of acute glomerulonephritis.
1-serum creatinine,urea &uric acid
2-Creatinine clearance
3-urine analysis
Lab request with the recommended laboratory investigations in a case of chronic renal failure.
1-complete urine analysis
2-serum creatinine,urea &uric acid
3-serum electrolytes:sodium,potassium
4-serum calcium&phosphorus
5-plasma bicarbonate

lab request with the recommended laboratory investigations in a suspected case of thyrotoxicosis

1-Serum T3(total&free)
2-SerumT4(total&free)
3-Serum TSH
4-Thyroid autoantibodies
lab request with the recommended laboratory investigations in parathyroid function disorders
1-serum calcium (total&ionized)
2-Serum phosphorus
3-serum parathyroid hormone(PTH)
lab request with the recommended laboratory investigations in cardiac disorders
1-serum total CK
2-serum CK-MB
3-cardiac troponins
4-serum lactate dehydrogenase
5-serum AST
lab request with the recommended laboratory investigations in lipid disorders
1-serum total cholestrol
2-serum triglycerides
3-serum HDL-C
4-serum LDL-C
Guidelines for Total Cholesterol levels

Triglycerides level

? For adults, fasting triglyceride levels are as follows:
Desirable: < 150 mg/dl .
Borderline high: 150 - 199 mg/dl .
High: 200 – 499 mg/dl.
Very high: ? 500 mg/dl.
? Triglycerides change dramatically in response to meals, increasing as much as 5 - 10 times higher than fasting levels few hours after eating.
? Sometimes high triglycerides are a sign of :
? Poorly controlled type 2 diabetes,
? Liver or kidney disease, or
? Side effect of taking medications such as beta blockers, birth control pills.

? Very high triglycerides (>1000 mg/dl) is a risk for developing pancreatitis.
Thank you with my best regards