ITC IRMA TruPoint Blood Analysis System - Manual (Page 125)

A.1
Appendix A
Limitations and Safety
Precautions
This appendix describes limitations of the IRMA TruPoint system.
LIMITATIONS
Measurements on the IRMA TruPoint analyzer are accurate and precise, as
shown in Appendix D, Performance Characteristics. However, sources of
error can arise from improper collection and handling of blood specimens
(pre-analytical errors) and certain physiological conditions.
COMMON SOURCES OF SAMPLING ERRORS
The IRMA TruPoint system was designed to eliminate many pre-analytical
errors associated with testing delays and sample storage and processing.
Analysis errors can arise from improper collection or handling of blood
specimens. These errors can be related to phlebotomy technique, heparin type
and concentration, speed of syringe fill, inadequate sample mixing, improper
storage of sample, and delays in analysis. The NCCLS Manual is an excellent
reference for sample collection and handling.
1, 6
The following sources of sampling error should be considered anytime test
results are inconsistent with the patient's condition or a previously established
trend:
Pre-Analytical Error
• The sample was not analyzed promptly after collection. Glycolysis by
leukocytes, platelets, and reticulocytes may cause pCO
2
and ionized
calcium values to increase, and pH, pO
2
, and glucose values to decrease. 9
• The sample was not collected anaerobically, resulting in room air
contamination. pH, pCO
2
, pO
2
, and ionized calcium values may change
due to exposure to room air. 9
• A sample was improperly stored.
> Samples chilled prior to analysis may result in falsely elevated
potassium values due to potassium leakage from erythrocytes and other
cells.
9
> Samples for pH and blood gases were not analyzed within 5 minutes of
collection, and were stored at room temperature, resulting in value
changes.