CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
Procedure
1. Wash hands and don gloves.
2. Assemble necessary equipment and supplies.
3. Assemble the pipetter with tips for accurate pipetting of the standards, controls,
and patient specimens. The tips should be changed between each sample
(including standards and controls) since carryover is possible between specimens.
Accurate pipetting is essential since extremely small amounts of standard,
controls, and patient specimens are required for this procedure.
4. Label the test tubes as follows for proper identification of blanks, standards, controls,
and unknowns: Label one tube “RB” for the blank specimen and one tube
“S” for the standard sample, and one or more tubes “C (number)” for the control
samples (e.g., C-1 and C-2 to differentiate between normal and abnormal controls).
The unknown samples [Sample (U) in the chart below] should be labeled by
patient name or other identifier such as a patient number.
5. Pipette the following volumes into the 13 × 100 tubes and mix well. Note that
the reagent is measured in mL and the specimens, standards, and controls are
measured in μLs (1000 μLs comprises 1 mL). The volumes indicated below may be
increased if the spectrophotometer requires a volume greater than 1.0 mL.
Reagent Blank (RB) Standard (S) Sample (U) Control (C)
Reagent 1.0 1.0 1.0
Standard – 0.01 –
Sample – – 0.01
6. Use the vortex mixer or gently swirl the mixture to briefly mix the contents of
each tube. Take care not to lose any of the sample and reagent mixture.
7. Allow all tubes to stand for ten minutes.
8. Arrange the cuvettes in the order in which they will be read after filling them from
the test tubes.
9. Insert the reagent blank into the well of the spectrophotometer and adjust the
absorbance to “0.”
10. Within 15 minutes of starting the procedure, read and record the absorbance
values for the standard (S) and the unknowns (U) versus the reagent blank (RB) at
500 nm.
11. Calculate the values for controls and the patient specimens (unknowns) by the
following equation.
Glucose Calculation (Manual Method)
Glucose (mg/dL) =
Abs of unknown (Au) × 10 (concentration of the
standard) (mg/dL)
Abs of standard (As)
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