Ischaemia-Modified Albumin Test for Venous Thromboembolism
Ischaemia-Modified Albumin Test for Venous Thromboembolism
Venous thromboembolism (VTE) is a relatively common condition, affecting about one person each year in every 1000 of the population. In 1998, the mortality from pulmonary embolism (PE) was 94 per one million of the population. Since then, the rate of diagnosis of PE has increased, without a notable reduction in mortality. The general population is aware of the risks of deep vein thrombosis (DVT), and the emergency department (ED) is a common portal for presentation with symptoms of VTE. It is standard practice to assess the clinical probability of PE or DVT and use D-dimer to exclude disease in the lower risk group. This avoids radiation exposure, admission and sometimes lengthy waits for diagnostic imaging.
To date, D-dimer is the only diagnostic blood marker for VTE. Poor specificity means it must be used in combination with clinical probability estimation. However, other biomarkers are influenced by VTE and remain on the whole, understudied. There may be a blood test with greater utility than D-dimer. DVT and PE form part of the same disease process, and there is evidence that half of the patients diagnosed with DVT also have significant embolic burden. A one-step unified approach for both DVT and PE would be easier to use and result in fewer errors.
Hypoxia and acidosis modify serum albumin transitional metal binding, to form ischaemia-modified albumin (IMA). Serum IMA is elevated in cardiac ischaemia, ischaemic stroke, bowel infarction and limb ischaemia. IMA levels were also found to be higher in case-control studies of DVT and PE patients in the ED.
The current approach to VTE diagnosis with clinical probability and D-dimer is not without problems. Several simple clinical probability scoring systems exist; however, emergency physicians are unable to remember these scores by rote. Moreover, emergency physicians are time pressured, which may contribute to further mistakes. A survey of emergency physicians demonstrated that one-third were unfamiliar with any PE score, and of those who were, 18% never used a score in the diagnosis of PE. Blood D-dimer testing is recommended to exclude VTE in patients with 'unlikely' clinical probability. Despite a relatively simple algorithm, diagnostic imaging can be ordered inappropriately, and D-dimer testing can be performed without clinical probability assessment. Poor compliance with diagnostic guidelines may contribute to the static mortality figures for VTE.
This study assessed the ability of the IMA assay to diagnose DVT and PE in a prospective cohort. The aim was to calculate the areas under the receiver operating characteristic (ROC) curves for all VTE, DVT and PE.
Introduction
Background
Venous thromboembolism (VTE) is a relatively common condition, affecting about one person each year in every 1000 of the population. In 1998, the mortality from pulmonary embolism (PE) was 94 per one million of the population. Since then, the rate of diagnosis of PE has increased, without a notable reduction in mortality. The general population is aware of the risks of deep vein thrombosis (DVT), and the emergency department (ED) is a common portal for presentation with symptoms of VTE. It is standard practice to assess the clinical probability of PE or DVT and use D-dimer to exclude disease in the lower risk group. This avoids radiation exposure, admission and sometimes lengthy waits for diagnostic imaging.
To date, D-dimer is the only diagnostic blood marker for VTE. Poor specificity means it must be used in combination with clinical probability estimation. However, other biomarkers are influenced by VTE and remain on the whole, understudied. There may be a blood test with greater utility than D-dimer. DVT and PE form part of the same disease process, and there is evidence that half of the patients diagnosed with DVT also have significant embolic burden. A one-step unified approach for both DVT and PE would be easier to use and result in fewer errors.
Hypoxia and acidosis modify serum albumin transitional metal binding, to form ischaemia-modified albumin (IMA). Serum IMA is elevated in cardiac ischaemia, ischaemic stroke, bowel infarction and limb ischaemia. IMA levels were also found to be higher in case-control studies of DVT and PE patients in the ED.
The current approach to VTE diagnosis with clinical probability and D-dimer is not without problems. Several simple clinical probability scoring systems exist; however, emergency physicians are unable to remember these scores by rote. Moreover, emergency physicians are time pressured, which may contribute to further mistakes. A survey of emergency physicians demonstrated that one-third were unfamiliar with any PE score, and of those who were, 18% never used a score in the diagnosis of PE. Blood D-dimer testing is recommended to exclude VTE in patients with 'unlikely' clinical probability. Despite a relatively simple algorithm, diagnostic imaging can be ordered inappropriately, and D-dimer testing can be performed without clinical probability assessment. Poor compliance with diagnostic guidelines may contribute to the static mortality figures for VTE.
This study assessed the ability of the IMA assay to diagnose DVT and PE in a prospective cohort. The aim was to calculate the areas under the receiver operating characteristic (ROC) curves for all VTE, DVT and PE.
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