Siemens RAPIDLAB 248, Operator'S Manual, Page: 20 / 135

Vacuum Tube Collection Systems
Vacuum tube systems containing lithium heparin can be used for
venous samples. Make sure the tube is filled completely, and the
samples are well mixed by gentle inversion.
Sample Handling
Significant errors in measurements on properly collected whole blood
samples may be caused by:
• metabolic changes in the sample occurring between sampling and
analysis,
• contamination of the sample by room air,
• improper mixing of the sample before measurement.
Minimize errors due to metabolic changes by analyzing samples as soon
as possible after collection. This is particularly important for
p O
2
samples, as oxygen is consumed during storage.
The rate of oxygen consumption is dependant on several factors; the
initial
p O
2
, the storage temperature, the white blood cell count, and the
reticulocyte count.
If samples will not be analyzed within ten minutes of collection, place
them in iced water. Samples stored in this manner may be kept for up
to 2 hours without significant change in values. Samples with high
white blood cell counts or high reticulocyte counts deteriorate more
rapidly, and should be analyzed immediately.
Improper mixing of samples before analysis may give erroneous results.
Blood cells settle during storage, and if not well mixed before sampling,
the results obtained can be higher or lower than the actual values.
Syringes should be rolled between the hands, and gently inverted
several times. Vacuum tubes should be gently inverted until the sample
is homogenous. Capillary samples must be thoroughly mixed by rolling
until homogenous. Clot formation may cause sample pathway blockages.
Reagents
WARNING
Wear safety glasses, gloves and a laboratory coat when
handling the reagents.
The reagents described in this section are for in vitro diagnostic use
only. Siemens cannot guarantee the performance of the system in any
of the following situations:
• Reagents other than those recommended are used.
• Expiry dates of reagents have been exceeded.
• Reagent ‘change by’ date has been exceeded.
• Reagents are not used or stored according to Siemens
recommendations.
• Standard laboratory practices are not followed.
• The procedures in this manual are not followed.
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