CAP Proficiency testing on the i-STAT/pCO2 negative bias
We have had a persistent negative bias for pCO2 on the CG4+ blood gas cartridge for the past year. I have reached out to Abbott for their recommendations and haven't heard anything back. Has anyone else experienced this and what have been your corrective actions? I am concerned because I have also had no response from Abbott regarding this study that was done a very long time ago.
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Am J Clin Pathol. 2000 Jul;114(1):128-38.
The rise and fall of i-STAT point-of-care blood gas testing in an acute care hospital.
Ng VL1, Kraemer R, Hogan C, Eckman D, Siobal M.
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Abstract
In response to a $350,000 laboratory budget cut and closure of an intensive care unit-based laboratory and a desire to maintain turnaround times of 10 minutes or less, a multidisciplinary group developed and implemented point-of-care (POC) testing. Only blood gases (pH, PO2, and PCO2) and ionized calcium values were deemed essential stat tests. Three commercially available POC blood gas devices were evaluated; all yielded results comparable to in-house reference methods. The 1 device with a US Food and Drug Administration-approved method for ionized calcium testing and with an existing interface for laboratory information systems was selected. Fiscal analysis predicted annual savings of approximately $225,000. POC blood gas analysis was implemented in April 1996 coincident with closure of the intensive care unit-based laboratory. Clinical laboratories and POC blood gas test volumes remained constant through August 1998; in contrast, the number of ionized calcium tests decreased dramatically after April 1996. In August 1998, clinically significant (i.e., artificial ventilation parameters would have been altered based on test results) discrepant PCO2 values were observed sporadically and noted only with patient specimens, not with commercial controls or electronic simulators. Because investigation failed to identify the cause, use of the POC device was discontinued in September 1998.
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Just thought about the PO2 issue; our first event was on either side of the mean (I think it was 2 neg and 3 pos if I remember correctly). The second event were mostly on the negative side but not by much. How the sample is applied to the cartridge impacts the results also. Those that do not follow the steady application of the sample have different outcomes from those that follow their training.
Has anyone that has contact CAP or Abbott gotten a response?
We use G3 cartridges and have a low bias as well, I don't question the sampling/storage techniques as I observed every sample performed. We don't report out pO2 for patient testing but do use SO2 which uses the PO2 for the calculation.
We are ordering a set of API proficiency samples to see where we fall in that peer group. We opened a ticket with Abbott to investigate and they had us send a box of the CG4+ to them.