Advice
The technology
The technology
CRP is a non-specific marker released into the blood in response to various infectious and inflammatory triggers. Measuring CRP in people presenting with suspected lower respiratory tract infection helps to differentiate viral and self-limiting infections from more serious bacterial infections that need antibiotics. Several clinical studies have evaluated point-of-care CRP testing in adults to guide antibiotic prescribing in respiratory tract infections when used along with clinical assessment (Aabenhus et al. 2014).
The Alere Afinion CRP test consists of the Afinion AS100 analyser and the Alere Afinion CRP assay. It is an in vitro diagnostic test intended to determine the amount of CRP in human whole blood, serum or plasma. It is a solid phase immunochemical assay which uses a membrane coated with anti-human CRP antibodies, which react with the CRP in the sample. The analyser measures the colour intensity of the membrane, and this is proportional to the amount of CRP in the sample.
The CRP test cartridge comes with an integrated blood sampling device which is used with a suitable lancet to collect a finger-prick blood sample. The sampling device is then inserted back into a test cartridge and placed into the analyser. The test cartridge contains all the reagents needed to measure CRP in a blood sample.
The CRP concentration is displayed on the analyser screen within 4 minutes. The measurement range is 5 to 200 mg/litre for whole blood, and 5 to 160 mg/litre for serum and plasma samples. The Afinion data connectivity converter is an optional component to the Alere Afinion CRP test. It allows for results from the Afinion AS100 analyser to be transferred to laboratory and hospital information systems.
Full information of the Alere Afinion CRP test procedure, quality control and accuracy and precision data can be found in the manufacturer's instructions for use.
The manufacturer also supplies assays for glycated haemoglobin (HbA1c), lipid panel and albumin creatinine ratio (ACR) that can be run on the Afinion AS100 analyser. However, these are beyond the scope of this briefing.
The innovation
Point-of-care CRP tests have the potential to change current practice by informing the clinical decision to prescribe antibiotics for people with symptoms of respiratory tract infections during a primary care consultation. Tests that improve clinical decision-making in antibiotic prescribing may support antimicrobial stewardship.
Testing for CRP is conventionally done by collecting a venous blood sample which is then sent for laboratory analysis, with the results being available 1 to 2 days later. Because of this delay, CRP testing is not typically used to assess acute infections in primary care, and is more commonly used when investigating chronic conditions.
Current NHS pathway
The decision to prescribe antibiotics for a suspected respiratory infection in primary care is generally made by a GP or nurse practitioner, and is based on medical history, clinical examination and assessment of risk.
Antibiotics can be prescribed at the time of the patient's first clinical examination (immediate), or prescribing could be postponed until a later time if symptoms have not resolved (delayed).
NICE's guideline on the diagnosis and management of pneumonia in adults recommends that point-of-care CRP testing should be considered for people with symptoms of lower respiratory tract infection in primary care if a diagnosis is unclear after clinical assessment, and that antibiotics should be prescribed based on the result. Immediate antibiotic treatment should be offered if the CRP level is more than 100 mg/litre and a delayed prescription should be considered at levels between 20 and 100 mg/litre. Antibiotics are not recommended for CRP levels less than 20 mg/litre.
NICE's quality standard on infection prevention and control states that in order to help prevent the development of antibiotic resistance in bacteria, it is important to prescribe antibiotics according to the principles of antimicrobial stewardship. These include prescribing antibiotics only when needed (and not for self-limiting mild infections such as colds and most coughs, sinusitis, earache and sore throats) and reviewing the continued need for them.
NICE is aware of the following CE-marked devices that appear to fulfil a similar function to the Alere Afinion system:
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AQT90 Flex (Radiometer Medical ApS)
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iChroma (Boditech Med)
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NycoCard Reader II (Alere)
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QuikRead go (Orion Diagnostica)
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Smart analyser (Eurolyser Diagnostica).
NICE has also published a medtech innovation briefing on the QuikRead go system for CRP testing in primary care.
Population, setting and intended user
The Alere Afinion CRP test would be done at the point of care in primary care for people with suspected bacterial lower respiratory tract infection. It would be done by primary care clinicians during a consultation. The Alere Afinion CRP test would only be used in conjunction with a clinical examination and clinical judgement to help inform the decision to prescribe antibiotics.
The Medicines and Healthcare Products Regulatory Agency (MHRA) guideline on management and use of IVD point-of-care test devices provides advice and guidance for point-of-care testing services in primary and secondary care. This guidance addresses important issues including arrangements for training, management, quality assurance and quality control, assessment by an external accreditation body, and consideration of available evidence for the performance of the test.
Costs
Table 1: Current costs of Alere Afinion CRP test components
|
Description |
Cost (£, excluding VAT) |
Additional information |
|
Afinion AS100 analyser |
1,200 |
Reusable |
|
Afinion CRP test cartridges |
3.50 |
Per test, available in packs of 15 |
|
Afinion CRP quality controls |
36 |
Ready-to-use controls, includes 2x0.5 millilitre level 1 controls (20 mg/litre) and 2x0.5 millilitre level 2 controls (60 mg/litre) |
|
Extended warranty |
100 |
Per year (from year 2); covers technical support and machine replacement (if faulty) |
The Afinion AS100 analyser requires no calibration and the only maintenance needed is cleaning of the cartridge chamber using a swab every month. A USB stick upgrade process provides the Afinion AS100 analyser with software updates.
The manufacturer provides both online learning videos and on-site training at no extra cost. On-site training is delivered by a member of a specialist support team and includes both practical and competence-based training sessions.
Costs of standard care
Standard care for people presenting to primary care with symptoms of a lower respiratory tract infection would be a consultation with a primary care clinician without the use of a point-of-care test to aid the diagnosis and the clinical decision to prescribe antibiotics. The unit cost of a GP consultation, excluding antibiotic prescription, ranges from £33 to £65, depending on duration (Personal Social Services Research Unit 2015). The average cost of a course of amoxicillin is approximately £1.49; a course of erythromycin costs approximately £3.05.
The Alere Afinion CRP test would be an adjunctive test to a primary care consultation, and so represents additional acquisition, consumable and staff time costs.
Resource consequences
The Alere Afinion CRP test will incur both capital and consumable costs, and there will be costs associated with maintenance and quality assurance. However, it may reduce costs by avoiding unnecessary antibiotic prescribing. Antimicrobial stewardship is an important issue in healthcare and a number of guidelines have been published in relation to this (NICE 2015, Public Health England 2015, Royal College of General Practitioners and Beech, NHS England 2015).
The NICE guideline on pneumonia in adults: diagnosis and management included a cost-utility analysis of generic CRP point-of-care testing. The use of CRP point-of-care testing was associated with an incremental cost of £18.92 compared with standard care, and an incremental quality-adjusted life year gain of 0.0012. The use of a CRP point-of-care test was judged to be cost effective, at an incremental cost-effectiveness ratio of £15,763.