19QUALITY CONTROL
Cholestech LDX System Procedure Manual
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Good laboratory practice principles suggest that external controls must be run whenever
the laboratory director has any question about test system integrity or operator technique
(e.g., when reagents may have been stored or handled in a way that can degrade their
performance or when operators have not performed a particular test in recent weeks).
If the controls do not perform as expected, repeat the test or contact Cholestech Technical
Service before testing patient samples.
The quality control results must be in range before testing patient samples. See the
Cholestech LDX System User Manual if they are not.
Please call Cholestech Technical Service at 800-733-0404 if you have any questions
regarding the manufacturer’s instructions for quality control.
3.4 Establishing and Calculating a Control Range
If the control materials you plan to use do not have ranges set for the Cholestech LDX, or if
you prefer to set your own ranges, please follow this procedure. Before you start, order an
adequate supply of control materials to last you several months. Do not order more than
you will use before the expiration date. You will need to follow this procedure to set ranges
for each level of control you use, and for each analyte you test for.
1. For each analyte, test a minimum of 20 replicates for each level of control material on
the Cholestech LDX. Record each result on the form provided.
a. Use one Control Range Calculation Form for each analyte and control level.
b. Assure all information is completed at the top of the data collection form.
c. If more than one Cholestech LDX Analyzer is in use in the laboratory, they should
all be used in determining the control range. The total number of results included
in the calculation should be at least 20, evenly run across the Analyzers.
2. You may calculate the statistics manually using the form provided by Cholestech or you
can use a statistical calculator computer program to do the calculations.
If you prefer, you can send or fax your results to Cholestech Technical Service at
800-733-0404, fax 510-732-7227. We will perform the calculations for you and send
the results and data calculations back to you.
3. Your control range should be set as the mean value plus or minus two standard
deviations (rounded off to the nearest integer).
For example:
If you calculate the mean to be 175 mg/dL and the standard deviation to
be 3.9 mg/dL, your acceptable control range would be:
175 mg/dL ± 8 mg/dL, or 167–183 mg/dL.
4. Record this control range on the Quality Control Log for that analyte, level and lot
number of control material.
5. When you run quality control samples, the results you get should fall within this range.
If the value of the control is outside these limits, then testing is considered to be out of control.
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