Technology overview

This briefing describes the regulated use of the technology for the indication specified, in the setting described, and with any other specific equipment referred to. It is the responsibility of healthcare professionals to check the regulatory status of any intended use of the technology in other indications and settings.

About the technology

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:

  • i‑STAT analyser – a handheld, battery‑operated and fully automated analysis platform, consisting of a LCD screen and keypad. Two versions of the i‑STAT analyser are available: a wireless internet version (the i‑STAT Wireless, which can upload the results wirelessly) and a non‑wireless version (with which test results can be uploaded when the analyser is placed in the i‑STAT downloader/recharger).

  • i‑STAT cartridges – single‑use, disposable cartridges for whole‑blood testing. They are inserted into the analyser after the blood sample has been applied. A large number of cartridges are available to test the most common test‑specific indicators in different combinations. Cartridges include tests for blood gases, electrolytes, metabolites and coagulation.

  • i‑STAT downloader/recharger – acts as a cradle for the analyser, automatically uploading data (with the non‑wireless analyser) and recharging its batteries.

  • Electronic simulator – for checking the performance of the i‑STAT analyser.

  • TriControls – a set of control solutions at 3 clinically relevant concentrations of test‑specific indicators for verifying each cartridge type.

  • i‑STAT data manager – data management software for cartridges, where test records can be transmitted to and then be printed or transmitted to the laboratory/hospital information system.

  • i‑STAT printer – an optional portable printer which enables the operator to print results at the point of care.

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:

  • lactate

  • pH

  • the partial pressure of carbon dioxide (PCO2)

  • the partial pressure of oxygen (PO2)

  • total carbon dioxide (TCO2; calculated)

  • bicarbonate (HCO3; calculated)

  • base excess (calculated)

  • oxygen saturation (sO2; calculated).

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

  • sodium

  • potassium

  • chloride

  • urea nitrogen/urea

  • glucose

  • creatinine

  • ionised calcium

  • total carbon dioxide (TCO2)

  • anion gap (calculated)

  • haematocrit

  • haemoglobin (calculated).

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:

  • dimensions of 209h x 64w x 52d mm and weight of 520 g

  • LCD display

  • keypad with a set of buttons for operating the i‑STAT analyser, including keys to enter information into the analyser and access the analyser's menu

  • battery‑operated using two 9 volt lithium batteries

  • communication link: infrared transmitter and receiver.

Both versions also have the same operator features:

  • Operator and patient information can be entered via a barcode scanner.

  • Screen prompts provide the user with step‑by‑step instructions during the entire testing process, displaying data in large type for easy reading.

  • An operator ID code to lock and unlock the i‑STAT analyser. This operator lockout helps prevent unauthorised users from performing or viewing test results.

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:

  • respiratory disturbances and metabolic and respiratory‑based acid‑base disturbances (blood gases)

  • hypoxia, shock, heart attack, severe congestive heart failure, renal failure, uncontrolled diabetes, or sepsis (lactate).

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

  • conditions that manifest electrolyte and acid‑base disorders (blood chemistry and TCO2)

  • anaemia, erythrocytosis, and blood loss related to trauma and surgery (haematocrit and haemoglobin)

  • parathyroid disease, various bone diseases, chronic renal disease, tetany, and disturbances related to surgical and intensive care (ionised calcium).

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:

  • Radiometer ABL800 FLEX analyser (Radiometer) – desktop blood gas analyser.

  • HemoCue 201+ meters (HemoCue) – portable systems that are used to measure haemoglobin.

  • FreeStyle Optium (Abbott) – portable blood glucose monitoring system.

  • FreeStyle Mini (Abbott) – portable blood glucose monitoring system.

  • epoc Blood Analysis System (Epocal) – portable blood gas and electrolyte testing.

  • RAPIDLab 348EX Blood Gas System (Siemens Healthcare Diagnostics) – desktop blood gas analyser.

  • RAPIDPoint 500 system (Siemens Healthcare Diagnostics) – desktop blood lactate assay.

Costs and use of the technology

The list price of the technology and consumables or maintenance required to use the products, excluding VAT, are as follows:

  • i‑STAT analyser: non‑wireless £5191, i‑STAT Wireless £6191.

  • i‑STAT downloader/recharger: £1100.

  • CG4+ cartridge: £12.49 per cartridge (unit size: box of 25 cartridges).

  • CHEM8+ cartridge: £19.54 per cartridge (unit size: box of 25 cartridges).

  • electronic simulator: £243.73.

  • TriControls: £20.31 (box of 10 glass ampules).

  • i‑STAT printer: £335.

  • service after 1 year warranty: £1298 per analyser per year.

The unit size for both CG4+ and CHEM8+ cartridges is 25 cartridges. The TriControls are supplied in a box of 10 glass ampules at a single concentration level (level 1, 2 or 3). Each level of TriControls needs to be purchased separately. Each analyser must be verified using a single cartridge. The TriControls used for both the CG4+ CHEM8+ cartridges are not stable, so a separate ampule must be used for each analyser being tested, although up to 3 i‑STAT analysers can be verified if tested simultaneously. Cartridges are verified by analysing level 1 and level 3 of the appropriate control on each new batch of cartridges and by comparing the results with the expected values published by the manufacturer. Verification of cartridges is not a manufacturer's system instruction but a suggestion to comply with quality assurance requirements.

The data management software is an optional component of the i‑STAT. It can be purchased from a third‑party vendor if an open system is needed to connect multiple devices. The software is typically installed in a server but could be installed on a computer with the correct specifications.

Likely place in therapy

The i‑STAT analyser with the CG4+ and CHEM8+ cartridges could be used in emergency departments to reduce the time taken for results compared with the same tests done in the hospital laboratory.

Specialist commentator comments

One specialist commentator stated that because the i‑STAT system is a compact and relatively simple machine to use, it can be a valuable addition to an ED if a blood gas analyser is not available, or if the time taken to get results from the laboratory regularly delays decision‑making. It could also be of benefit in minor injury units without access to on‑site laboratory services.

One commentator mentioned that almost all EDs have point‑of‑care blood gas machines already, so the benefits of these cartridges in reducing time to discharge are overstated. Another commentator stated that if on‑site laboratory services are available and results are generally ready in a reasonable timescale, the i‑STAT does not confer a huge advantage to the speed of decision‑making or total length of ED stay.

Two specialist commentators stated that the CHEM8+ and CG4+ cartridges do not include some of the additional tests that are used to help decide if a patient can be sent home safely, such as d‑dimer, troponin and white cell count, although cardiac troponin I is available on another i‑STAT cartridge. Therefore, even with the i‑STAT, other tests may be needed in some instances. One specialist commentator was of the opinion that the i‑STAT analyser may also take up clinical time to carry out quality control checks and to test the sample, rather than leaving this to laboratory staff outside the ED.

Another specialist commentator stated that from a financial point of view, the cost per test when using the i‑STAT is much higher than an on‑site laboratory analysis.

Equality considerations

NICE is committed to promoting equality and eliminating unlawful discrimination. In producing guidance, NICE aims to comply fully with all legal obligations to:

  • promote race and disability equality and equality of opportunity between men and women

  • eliminate unlawful discrimination on grounds of race, disability, age, sex, gender reassignment, pregnancy and maternity (including women post‑delivery), sexual orientation, and religion or belief (these are protected characteristics under the Equality Act 2010).

Young children, older people and people with chronic conditions are more likely to need the services of an ED. These groups in particular will benefit from improvements in the quality of ED care. Using point‑of‑care tests could contribute to quality of care if outcomes such as time to a clinical decision improve. Age is a protected characteristic under the 2010 Equality Act.