pCO2 correlations i-STAT vs RapidPoint500
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Is there anyone in POC land that does correlations between i-STAT blood gases and RapidPoint 500 gases? If so, how are your correlations for pCO2 between these two methods? I have excellent correlations for pH and pO2, but the pCO2 shows a consistent positive bias for the i-STAT that it outside the CLIA allowable error of 5 mmHg or 8%
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Hi Tracy. We do comparison's between the istat and our RP's. We just did one in June and it fell within the allowable limit for the pCO2. I'm curious if others are having issues though.
Jessica,
What I-STAT cartridge type do you use for your correlations? What is your allowable error for your pCO2 comparison?
Thanks!
Hi Tracy,
We do our CG4 cartridges against the C500's in our Chemistry lab. We do correlations every 2 months with our new shipments and have only had 2 this year that have been out.
Tracy,
We do correlations between the iStat and the RP500 and also see the difference for pCO2. My understanding is that when it comes to different instruments there may be a difference greater than the CLIA allowable difference. This may be due to different methodologies and different instrumentation and procedures.
As long as the difference is acknowledged and the users are aware of it, you are not out of compliance, unless your institution's policy says otherwise.
We state in our correlation policy that any methodology biases should be reported to the unit with the point of care instrument and posted on our hospital's share drive.
We do correlations between the iSTAT and the RP500 and the pCO2 does usually read higher on the iSTAT but within our acceptable limits. We use a different mechanism to determine acceptability but looking at our results we are within 10% mmHg. Of note the pO2 goes the other way, RP is higher, which would be expected. I always fill the iSTAT cartridges first since the RP sampling leaves a dead space which could impact results. We use all 3 of our BG cartridges in use (G3, CG4, CG8) and even those have variations. Blood gases are simply tricky.