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 VL1Kraemer RHogan CEckman DSiobal M.

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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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We are seen a negative bias too for pO2 and pCO2. We will be contacting CAP as well as Abbott regarding tis issue.


Thanks for reporting it.

Hi Vivian, it's frustrating Abbott isn't responding.  We've retested the spare set of samples after submission to see what an med tech could get and our numbers were again on the low side of the mean.  We have three experienced perfusionists that perform this test and have it rotated among.  This is the second time we have an unacceptable grade on the pCO2 (last time was 2017) and we were one point out!

What internal RCA have you done for this?  We do have a process where we work through eliminating clerical error, sample handing error (possible), systemic error etc.

Hi Karen, I just called Abbott and opened a case for them to investigate our issue. We are using the EG+7 cartridges and the pCO2 is on the low side on the original and repeated samples. CAP also suggested to send them the documentation to show the bias in your institution. Right now the operator enters the data directly into the CAP answer sheet. We are going to have a pWEB print out to make sure there is no transcription error. We are going to monitor closely the technique. Document the time the samples are at RT, the time they were tested and make sure there are no bubbles.



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