2.1 Acute kidney injury ranges from minor loss of kidney function to complete kidney failure. In current practice, reduced kidney function is identified, and staged, by elevated serum creatinine levels or reduced urine output, or both. There are no direct treatments for most types of acute kidney injury. Care focuses on optimising haemodynamics and fluid status, avoiding nephrotoxic treatments, and identifying and resolving the underlying cause as quickly as possible. A goal of care is to prevent further kidney injury and stop acute kidney injury progressing; in particular, to prevent it progressing to a stage when renal replacement therapy is needed.
2.2 The NephroCheck and neutrophil gelatinase-associated lipocalin (NGAL) tests could potentially detect kidney injury earlier than current methods for monitoring kidney function: serum creatinine and urine output. Serum creatinine levels are slow to rise after kidney injury. Also, using intravenous fluids and diuretics can cause issues when detecting kidney injury by measuring urine output. Earlier identification of acute kidney injury could allow earlier adoption of measures such as care bundles (a group of interventions, or processes, which when implemented together can help to reduce the severity of acute kidney injury). These could prevent the condition progressing to more severe injury and reduce the risk of adverse outcomes for patients.
2.3 The NephroCheck test is indicated for use in people who are critically ill, but the NGAL tests potentially have a broader indication. At the scoping workshop and assessment subgroup meeting, clinical experts considered the most relevant population for this assessment. They considered the different types of care for people who are critically ill to determine who could benefit from use of the tests in the NHS. People who are admitted to NHS critical care should already have a range of interventions designed to prevent acute kidney injury because they are extremely unwell. Therefore, the potential for the tests to improve outcomes in this population is limited in the NHS because the results of the tests are unlikely to change management decisions. Clinical experts highlighted that the tests could be useful for people who are being considered for admission to critical care; that is, when a decision about admission has not been made and the test results could guide the use of preventive care for acute kidney injury. The decision question for this assessment therefore focuses on this population.
2.4 The NephroCheck test (Astute Medical) measures the level of 2 biomarkers (tissue inhibitor of metalloproteinase 2 [TIMP‑2] and insulin-like growth factor binding protein 7 [IGFBP‑7]) in urine and uses the concentrations to help assess risk of moderate to severe acute kidney injury (defined as per the Kidney Disease Improving Global Outcomes [KDIGO] guidelines) in the subsequent 12 hours. The company states that the test result is intended to be used in conjunction with clinical evaluation as an aid in the risk assessment of acute kidney injury in the critically ill.
2.5 The concentrations of TIMP‑2 and IGFBP‑7 are used to calculate an AKIRisk score (the concentrations of each [nanograms/millilitre; ng/ml] are multiplied together and divided by 1,000). A score of over 0.3 indicates a higher risk of developing moderate to severe acute kidney injury within 12 hours of assessment. The test can be run on the Astute 140 meter, the VITROS 3600 immunodiagnostic system and the VITROS 5600 and VITROS 7600 integrated system clinical chemistry analysers. The company states that the test is marketed in the UK for people over 21 years.
2.6 The ARCHITECT and Alinity i Urine NGAL assays (Abbott) are chemiluminescent microparticle immunoassays for the quantitative determination of NGAL in human urine. The company states that for diagnostic purposes, the test results should be used in conjunction with clinical assessment and the results of any other testing that has been done.
2.7 The company has no set threshold for a positive result. The ARCHITECT and Alinity i Urine NGAL assays are run on different analysers but use the same reagents. The ARCHITECT assay is run on the ARCHITECT system (i1000SR, i2000, i2000SR, ci4100, ci8200 or ci16200). The test has no age restrictions on use.
2.8 The BioPorto NGAL test (BioPorto Diagnostics) is a particle-enhanced turbidimetric immunoassay for the quantitative determination of NGAL in human urine, ethylenediaminetetraacetic acid (EDTA) plasma and heparin plasma. The company states that this is not a standalone test and clinicians should interpret the significance of any raised NGAL level alongside a person's clinical features.
2.9 The company advises that the NGAL concentration in an isolated sample of urine or EDTA plasma should exceed 250 ng/ml to indicate the presence of renal disorder, including acute kidney injury. The assay can be run on various clinical chemistry analyser systems in a laboratory. The test has no age restriction on use.