FOR STUDENTS

1. Dr. Vishnu Kumar
Professor, Department of
Biochemistry, SRMSIMS, Bareilly
vkawasthi@hotmail.com
madhwapur1976@gmail.com
QUALITY CONTROL

2. Learning Objectives
After completion of this lecture
learner should be able to define :
 Quality Control
 Internal Quality Control
 External Quality Control
 Accuracy, Precision
 Shift & Trend Error

3. QUALITY CONTROL
Definition:
It is the procedure that is used to asses the
analytical phase of patients’ investigation.
In other words this is the technique used to
ensure that the best quality of performance
is maintained.

4. Purpose
• To ensure reliability of each measurement
performed on a sample.

5. ERROR
• Error: In spite of all efforts mistakes may
be there. So we can minimize errors but
cannot avoid it totally. If the errors are
promptly detected, corrective action can
be taken.
• Mistake: A mistake is an avoidable error.

6. EXTERNAL QUALITY CONTROL
• A central reference laboratory sends a
lyophilized sample containing a known
quantity of a substance, this is analyzed in a
peripheral laboratory. The result will be
compared with those of the group of other
participating peripheral laboratories and also
of the central laboratory.

7. EXTERNAL QUALITY CONTROL
contd..
• If the result of the peripheral laboratory is
comparable with those of the central laboratory
and other peripheral laboratories, the
arrangements available in the said peripheral
laboratory are said to be reliable. This type of
checking is done once or twice in a month.

8. INTERNAL QUALITY CONTROL
• The peripheral laboratory itself makes a
reference standard serum sample and
checks the results on daily basis.

9. ACCURACY
• It is the closeness of the result with the
true value. Values more away from the
true value are less accurate. For example
the 1st technician gets 99 mg% glucose,
2nd technician gets 95mg% on a sample
with true value 100 mg%, then the value of
the 1st technician is accurate.

10. PRECISION
• How closely the measured values
compare with each other.
• This refers to the reproducibility of the
result.
• Precision depends on the technique,
reagent as well as on the technical ability
of the technician.

11. PRECISION contd..
• For example a technician performs glucose
analysis on the same sample on three different
occasions, and obtains 100 mg%, 99 mg% and
101 mg%, the results have been reproduced
very well and the precision is very good.

12. SHIFT AND TREND
• A shift is defined as a change in QC result that
happens abruptly and continues in the same
level. A shift is a sudden change of values
from one level of the control chart to amother.
• A common cause of a shift is failure to
recalibrate when changing lot numbers
reagents during an analytical run.
• A trend is defined as a gradual change in one
direction in QC recovery.