i STAT CG4+ and CHEM8+ cartridges for point-of-care testing in the emergency department

CE marking

The CG4+ and CHEM8+ cartridges (Abbott) are classified as IVD General in vitro diagnostic medical devices (98/79/EC). The CG4+ cartridge was CE marked in October 2003 and the CHEM8+ cartridge in December 2006.

Description

The i‑STAT is a handheld, in vitro analyser designed to be used at the patient's bedside (point‑of‑care) for testing arterial, venous or capillary whole blood. It takes single‑use cartridges containing chemically sensitive biosensors on a silicon chip that are configured for test‑specific indicators. i‑STAT test cartridges are available for a broad range of diagnostic and treatment indicators including blood gases, electrolytes, metabolites and coagulation markers. Blood samples do not need to be processed before testing and results are available in around 2 minutes.

The i‑STAT system has the following components, accessories and consumables:

This briefing report focuses on 2 i‑STAT cartridges, the CG4+ and CHEM8+, which are most relevant to the NHS ED setting.

The CG4+ cartridge provides the following chemistry test and blood gas measures:

The CHEM8+ cartridge provides the following electrolyte and haematology tests:

Detailed information on the cartridges and tests is available on the manufacturer's website, including their intended use, methods and performance data on the tests.

To use a test cartridge, the operator and patient information is entered into the i‑STAT analyser using the keypad. Two or 3 drops of blood (between 65 and 95 microlitres) are applied to the cartridge using a syringe before the cartridge is inserted into the i‑STAT analyser. The test starts automatically once the cartridge is inserted in the analyser. All the tests are run simultaneously and results are available in around 2 minutes for both the CG4+ and CHEM8+ cartridges. Before running a test, each cartridge initiates a series of pre‑set quality control diagnostics, from monitoring the quality of the sample to validating the reagent. Test results are displayed on the LCD screen of the analyser and can be uploaded automatically, either wirelessly with the i‑STAT Wireless or when the analyser is placed in the i‑STAT downloader/recharger. The data can be transmitted from multiple analysers in many patient care areas to the i‑STAT Data Manager, a dedicated desktop computer with the i‑STAT central data application installed. The data can be printed, stored, organised, edited and transferred to a laboratory information system or other computer system such as a hospital information system to aid patient record keeping.

The manufacturer's instruction suggests that an electronic quality control check of the performance of each i‑STAT analyser should be done once on each day of use, or as needed. This is carried out with an electronic simulator (either internal or external), which tests the analyser's cartridge signal‑reading function. When the specified time has passed since the last electronic simulator test the internal test will automatically be performed when a cartridge is inserted and before the sample is tested. This adds about 20 seconds to the testing cycle. The external electronic simulator is a device in a cartridge form. It is inserted into the cartridge port to perform the check. Using the external electronic simulator adds about 60 seconds to the test cycle. The electronic simulator check simulates 2 levels of electrical signals that stress the analyser's cartridge signal detection function both below and above measurement ranges. This provides an independent check of the analyser's ability to take accurate and sensitive measurements of voltage, current and resistance from the cartridge. An analyser will pass or fail this electronic test depending on whether or not it measures these signals within limits specified in the analyser software.

The integrity of i‑STAT cartridges can be verified using 2 of the 3 TriControls, which are control fluids formulated at 3 clinically relevant levels with known concentrations of the test-specific indicators. Cartridges can be verified on 1 representative cartridge from each new batch of cartridges and by comparing the results to the expected values published by the manufacturer in the value assignment sheets. To verify the CG4+ and CHEM8+ cartridges, level 1 (low concentration) and level 3 (high concentration) controls are used.

Both versions of the i‑STAT analyser have the following specifications:

Both versions also have the same operator features:

Setting and intended use

The i‑STAT analyser and cartridges can be used for multiple indications in multiple settings. The focus of this briefing is the intended use of the CG4+ and CHEM8+ cartridges in the ED setting to aid the diagnosis or exclusion of numerous potentially serious diseases and clinical conditions. The CG4+ cartridge is used for the measurement of blood gases and lactate that are indicative of the following conditions:

The CHEM8+ cartridge is used for tests of blood chemistry, haematology, ionised calcium and total CO₂ to help diagnose:

The manufacturer stated that the analysers and cartridges should be used by healthcare professionals trained and certified to use the system. Each end‑user should attend an end‑user training class in order to receive certification for the i‑STAT system. The class includes hands‑on demonstration and a competency assessment.

Current NHS options

In the majority of NHS EDs, standard blood tests (such as those available with the CHEM8+ cartridge) are obtained from accredited hospital laboratories, usually on site. Blood gases and lactate measurements are also analysed in hospital laboratories, although a specialist commentator stated that most EDs now have standalone analysers to measure lactate when testing for sepsis. Standalone blood gas analysers are also used in intensive care units where blood gases are measured frequently.

NICE is aware of other CE‑marked point‑of‑care test devices that appear to fulfil a similar function to the i‑STAT CG4+ and CHEM8+ cartridges on an individual test basis. These include handheld devices but also desktop analysers which can be used to provide point‑of‑care tests in the ED. Examples of these devices include: