Introduction
part B
 How does clinical biochemistry help in patient
 health care?.
 Different categories of biochemical test.
 Sample’s tubes and types.
Request form.
(& types of biochem.
Tests)
2. Sample obtained.
( & examples of errors)
3. Transit to Lab.
1.
4.
Reception.
5.
Analysis.
6.
Quality control.
7.
Collation and
reporting.
8.
Interpretation.
Blood
Specimens
Plasma
Blood collected into a tube containing
anticoagulant. A sample undergoes
centrifuging process, a supernatant is
called PLASMA.
Serum
Blood collected into a plain tube and
allowed to clot. After a sample undergoes
centrifuging process, a supernatant is
called SERUM.
Whole blood
Blood collected into a tube containing an
anticoagulant with no further handling.
• Normal appearance of plasma and serum is CLEAR PALE YELLOW
COLOR.
• Abnormal appearance may be due to disease or improper handling of the
sample.
- RED-colored : RBCs destruction.
- DEEP YELLOW OR OGRANGE ( ICTERUS ) : presence of bilirubin.
- MILKY OR TURBID : presence of fat.
Wrong
technique
May lead to false results as false hemolysis or high potassium.
Prolonged
stasis in
venipuncture
This causes diffusing of plasma from blood vessels into
interstitial space leading to false high results of plasma proteins
such as calcium and thyroid hormones.
Inaccurate
timing
Common in 24-h urine sample.
Wrong
container
- Blood samples for lipid tests collected into tube with
anticoagulant
- Blood sample for a glucose is collected into a tube containing
fluoride.
- Obtain a new sample if the original one were put in a wrong
container.
Inappropriate
sampling site
- No sample should be taken from DOWNSTREAM an IV drip/
- - An arm in which 5% glucose is infused, must spared.
Inappropriate
storage
Generally, a blood sample should not stored overnight to avoid
leakage of RBCs components ( false high K. PH, LDH-ase )
 A blood sample should be transferred IMMEDIATELY
to lab to be processed properly.
 Other specimen may require specific precautions .
 Any new sample received by lab reception will get
specific serial number and bar code.
 Many of biochemistry lab tests are done in automated
manners.
 Biochemical measures vary for two reasons:
A) Analytical variation.
B) Biological variation.
 Quality monitored in two levels:
 Internal quality control.
 External quality control .
 Once the results are available they are collated and
report is issued.
 The laboratory report should include :
 Patient information.
 Results of analysis.
 Normal values ( references )
 Normal values “ reference “ represent the normal
healthy state.
 A person not having any disease with abnormal lab
result is a FALSE POSITIVE.
 A person has a disease but normal lab result is a FALSE
NERGATIVE.
 Clinician should follow both absolute value and
accumulative value.
 If test’s results is unexpected or can not be explained,
a decision to repeat the test is made after discussion
with the office.
 Sex e.g. serum creatinine
 Stress and anxiety.
is higher in men
 Age e.g. ALK enzyme is
higher in children
 Diet e.g. TG should
measured after 14-h.
 Time e.g. certain
hormones has a peak
tendency.
 Exercise
 posture
 Medical condition.
 Pregnancy
 Menstrual cycle
 Drug history
 After interpretation of the results, the answer for a
clinical question is reached.
1.
Core biochemical test
 Na, K, Urea, creatinine, HCO3, Ca, Ph, Alb, Total protein,
Bilirubin, ALK, ALT, AST, T4, T3, TSH, γGT, CK, blood
gases, glucose, amylase.
Specialized tests
 Vitamines, Drugs, Lipids, DNA analyses, Trace element,
Hormons.
2.
Emergency test
 Urea and electrolyte, Blood gases, glucose, amylase, Ca,
paracetamole.
3.