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1 MLAB 2401: Clinical Chemistry Chapter 3: Basic Principles and Practice of Clinical Chemistry, part 2.

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Presentation on theme: "1 MLAB 2401: Clinical Chemistry Chapter 3: Basic Principles and Practice of Clinical Chemistry, part 2."— Presentation transcript:

1 1 MLAB 2401: Clinical Chemistry Chapter 3: Basic Principles and Practice of Clinical Chemistry, part 2

2 General Laboratory Equipment Balances – type chosen dependent on volume/weight needed and degree of accuracy required.  Harvard Trip Balance A mechanical type with two pans Put desired weight on one end and desired substance on other  Top-loading Balance – single pan, electronic readout  Analytical Balance Very elaborate, accurate and most costly Has a single pan behind sliding doors and uses mechanical I 2

3 General Laboratory Equipment Centrifuge  Purpose:separating solids from a liquid suspension by means of centrifugal force  Types  Characteristics Fixed rotor head / swinging bucket Closing – locked closed lid now required 3

4 General Laboratory Equipment Other methods of separating materials  Filtration of materials  Dialysis - This method makes use of a semi-permeable membrane that allows separation of molecules using their size 4

5 Specimen Collection and Processing Medical ethics in specimen collection – professionalism and confidentiality at all times  Special collection procedures Fasting specimens: overnight for most tests, 12 hours for lipid studies Timed interval specimens  Examples include glucose tolerance, therapeutic drug monitoring, and hormone stimulation testing  In some cases urine collection also required Legal chain of evidence Other special collection procedures 5

6 Specimen processing Determining specimen acceptability  Other than improper timing, identify things that can affect chemical analysis of clinical specimens. Specimen accessioning 6

7 7 Specimen processing  Serum separators – Gel barrier Plastic tube device

8 SPECIMEN CONSIDERATIONS Specimen collection and processing are critical A poor specimen = poor specimen results Most lab errors are pre-analytical !!! Common sources of error Contamination with IV fluids Hemolysis of RBCs contaminates plasma and serum Labeling errors Collection with improper anticoagulants and preservatives Analyzers clogged by clotted specimens 8


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