Did You Know?

One such analyzer is the i-STAT. Because of this analyzer’s design, a facility that operates several i-STATs does not have to perform quality control (QC), method comparisons, performance verifications, and calibration verifications on each individual i-STAT analyzer.

This month, we take a close look into testing for i-STAT analyzers:

• Only one i-STAT analyzer needs to be tested during performance verification studies at installation and during semi-annual method comparison studies.
• ACHC does not require calibration verification for the i-STAT every six months.
• The thermal probe check must be verified every six months.

i-STAT Technology Description

The i-STAT is a cartridge-based “analyzer” with all the analytical requirements for the performance of a test contained within an individual cartridge. The test sample and reagents never enter the analyzer, which transforms electrical signals from the test cartridge into human-readable results. Because the sample makes contact only with the cartridge, the analyzer does not get dirty or require regular maintenance beyond a simple electronic QC check each day of use and a wipe clean as required. The user cannot run a cartridge without having performed the electronic QC check.

All i-STATs that pass the electronic simulator test are considered equivalent. Therefore, it is only necessary to use one i-STAT that passes the simulator test for compliance with regulatory and accreditation requirements for:

• Initial performance verification studies.
• Initial calibration verification.
• Proficiency testing.
• Method comparisons within the laboratory.

How the Electronic Simulator Works

Here’s how the electronic simulator works and its impact on method comparisons and performance verifications:

“An Electronic Simulator, which mimics the electrical characteristics of the signals produced by the sensors, is inserted into the handheld analyzer on a daily basis. The Simulator produces signals consistent with both very low and very high concentrations of each of the analytes. The handheld analyzer causes the Simulator to change the signals via a control signal. The software in the handheld analyzer measures these signals as it would measure signals from a cartridge. The software checks the measurements against predetermined thresholds and indicates their acceptability to the user via a PASS/FAIL message. All analyzers that pass the Electronic Simulator test are equivalent.”

i-STAT QC Requirements

The electronic simulator does not check the cartridges. Therefore, the manufacturer’s recommendation for cartridge QC is to analyze multiple levels of external QC on each new lot number and shipment of cartridges. The external QC (per new lot number or shipment) can be performed on one analyzer; it is not necessary to perform QC on each analyzer. An individualized quality control plan (IQCP) should be written and used for all non-waived tests to eliminate the Clinical Laboratory Improvement Amendments (CLIA) requirement of two levels of QC per each day of testing for non-waived testing.

i-STAT and Calibration Verification

Calibration is automatically performed as part of the test cycle on each cartridge. Therefore, no further calibration procedures, including calibration verification, are required by ACHC. Every cartridge contains a sealed foil pack with a known concentration of each analyte in a calibrant solution.

During the first part of the testing cycle, the calibrant solution is forced out of the foil pack and over the sensors. The signals produced by the sensors in response to the calibrant solution are stored. Once this sequence is completed, the analyzer automatically moves the sample over the sensors.

By comparing the sensors’ response to the sample with the response to the calibrant, the concentration of each analyte in the sample is calculated. An error message will be displayed if calibration fails. If calibration fails, patient results will not be displayed, and the sample will need to be reanalyzed with a new cartridge.

The Standard

Standard 06.05.00: Calibration and Calibration Verification Procedures §493.1255(a)(1), (2)(i-iii), (3): Calibration and calibration verification procedures are required to substantiate the continued accuracy of the test system throughout the laboratory’s reportable range of test results for the test system.

Check your Accreditation Requirements for Clinical Laboratories manual to read the complete Standard 06.05.00 for testing requirements and other procedures.

Thermal Probe Check Verification

A quality check is performed on the thermal probes each time the external electronic simulator is used. The surface temperature of the external electronic simulator must not fluctuate.

If this condition is not met, the thermal probe check is not completed. Therefore, i-STAT recommends that the thermal probe check be verified every six months. ACHC Standards require that manufacturer recommendations be followed.

References

i-STAT System Manual, Abbott Point of Care; March 7, 2013

The Clinical Biochemist Reviews, 2010 Aug; 31(3): 81-84