Novel SUN dipstick identifies advanced acute kidney injury at bedside

ATLANTA – A novel, low-resource bedside diagnostic tool that measures saliva urea nitrogen appears useful for identifying patients with advanced acute kidney injury who have an increased likelihood of requiring dialysis.

In a study involving 44 patients, the tool – a dipstick that measures saliva urea nitrogen (SUN), a marker of kidney function – reliably discriminated Acute Kidney Injury Network (AKIN) stage 3 AKI from earlier AKI stages, Dr. Roberto Picoits-Filho reported at Kidney Week 2013.

SUN, as measured using the dipstick, was significantly correlated with blood urea nitrogen, or BUN (R_s = 0.77), irrespective of AKIN stage or AKI etiology, Dr. Picoits-Filho reported during a press briefing at the conference, which was sponsored by the American Society of Nephrology

The diagnostic performances of the tests were comparable: For SUN, the area under the curve of a receiver operating characteristic curve (AUC ROC) was 0.76, and for BUN the value was 0.69, he said.

"We saw that the test was actually very good, particularly in patients with very severe stages of kidney injury, which is important, because those are the patients who most likely will need to go into dialysis or more complex treatment," said Dr. Picoits-Filho of the Pro-rim Foundation and Pontifícia Universidade Católica do Parana, Curitiba, Brazil.

Patients included in the study were adults (mean age, 59.5 years; 58% women) who were hospitalized with prerenal (67%), renal (24%), or postrenal (9%) suspected AKI. A third had AKIN stage 1 disease, 27% had stage 2 disease, and 40% had stage 3 disease.

Unstimulated saliva was applied to the dipstick to measure whether SUN concentrations were 5-14, 15-24, 25-34, 35-54, 55-74, or 75 or greater mg/dL; BUN was measured concomitantly.

The findings are notable because while AKI in the intensive care unit setting is usually due to acute tubular necrosis, a large proportion of AKI cases outside of the ICU are due to prerenal AKI, which is reversible if diagnosed early and treated aggressively, Dr. Picoits-Filho said.

One way of detecting AKI early on in both the hospital and outpatient settings is by criteria defined by recent consensus: "basically by glomerular filtration rate, but also by urine output," he said.

By using serum creatinine to estimate GFR, you can actually detect patients with AKI. This defines risk for developing more severe AKI (and can help in preventing the need for renal replacement therapy), and also predicts in-hospital mortality, he said.

"The problem is that you need a laboratory facility to get this measurement, and this is not always available, especially in remote areas of the world," he added.

The current findings suggest the SUN dipstick could improve the diagnosis of advanced AKI and aid in triaging patients – particularly in remote areas with limited access to clinical chemistry facilities – and may improve outcomes, he said.

While the test did not prove efficient as a screening tool for chronic kidney disease, it could potentially have a role in monitoring those with chronic kidney disease, he noted.

This study was supported by the Renal Research Institute, New York, and the International Society of Nephrology. Dr. Picoits-Filho reported having no other disclosures.

ATLANTA – A novel, low-resource bedside diagnostic tool that measures saliva urea nitrogen appears useful for identifying patients with advanced acute kidney injury who have an increased likelihood of requiring dialysis.

In a study involving 44 patients, the tool – a dipstick that measures saliva urea nitrogen (SUN), a marker of kidney function – reliably discriminated Acute Kidney Injury Network (AKIN) stage 3 AKI from earlier AKI stages, Dr. Roberto Picoits-Filho reported at Kidney Week 2013.

SUN, as measured using the dipstick, was significantly correlated with blood urea nitrogen, or BUN (R_s = 0.77), irrespective of AKIN stage or AKI etiology, Dr. Picoits-Filho reported during a press briefing at the conference, which was sponsored by the American Society of Nephrology

The diagnostic performances of the tests were comparable: For SUN, the area under the curve of a receiver operating characteristic curve (AUC ROC) was 0.76, and for BUN the value was 0.69, he said.

"We saw that the test was actually very good, particularly in patients with very severe stages of kidney injury, which is important, because those are the patients who most likely will need to go into dialysis or more complex treatment," said Dr. Picoits-Filho of the Pro-rim Foundation and Pontifícia Universidade Católica do Parana, Curitiba, Brazil.

Patients included in the study were adults (mean age, 59.5 years; 58% women) who were hospitalized with prerenal (67%), renal (24%), or postrenal (9%) suspected AKI. A third had AKIN stage 1 disease, 27% had stage 2 disease, and 40% had stage 3 disease.

Unstimulated saliva was applied to the dipstick to measure whether SUN concentrations were 5-14, 15-24, 25-34, 35-54, 55-74, or 75 or greater mg/dL; BUN was measured concomitantly.

The findings are notable because while AKI in the intensive care unit setting is usually due to acute tubular necrosis, a large proportion of AKI cases outside of the ICU are due to prerenal AKI, which is reversible if diagnosed early and treated aggressively, Dr. Picoits-Filho said.

One way of detecting AKI early on in both the hospital and outpatient settings is by criteria defined by recent consensus: "basically by glomerular filtration rate, but also by urine output," he said.

By using serum creatinine to estimate GFR, you can actually detect patients with AKI. This defines risk for developing more severe AKI (and can help in preventing the need for renal replacement therapy), and also predicts in-hospital mortality, he said.

"The problem is that you need a laboratory facility to get this measurement, and this is not always available, especially in remote areas of the world," he added.

The current findings suggest the SUN dipstick could improve the diagnosis of advanced AKI and aid in triaging patients – particularly in remote areas with limited access to clinical chemistry facilities – and may improve outcomes, he said.

While the test did not prove efficient as a screening tool for chronic kidney disease, it could potentially have a role in monitoring those with chronic kidney disease, he noted.

This study was supported by the Renal Research Institute, New York, and the International Society of Nephrology. Dr. Picoits-Filho reported having no other disclosures.

ATLANTA – A novel, low-resource bedside diagnostic tool that measures saliva urea nitrogen appears useful for identifying patients with advanced acute kidney injury who have an increased likelihood of requiring dialysis.

In a study involving 44 patients, the tool – a dipstick that measures saliva urea nitrogen (SUN), a marker of kidney function – reliably discriminated Acute Kidney Injury Network (AKIN) stage 3 AKI from earlier AKI stages, Dr. Roberto Picoits-Filho reported at Kidney Week 2013.

SUN, as measured using the dipstick, was significantly correlated with blood urea nitrogen, or BUN (R_s = 0.77), irrespective of AKIN stage or AKI etiology, Dr. Picoits-Filho reported during a press briefing at the conference, which was sponsored by the American Society of Nephrology

The diagnostic performances of the tests were comparable: For SUN, the area under the curve of a receiver operating characteristic curve (AUC ROC) was 0.76, and for BUN the value was 0.69, he said.

"We saw that the test was actually very good, particularly in patients with very severe stages of kidney injury, which is important, because those are the patients who most likely will need to go into dialysis or more complex treatment," said Dr. Picoits-Filho of the Pro-rim Foundation and Pontifícia Universidade Católica do Parana, Curitiba, Brazil.

Patients included in the study were adults (mean age, 59.5 years; 58% women) who were hospitalized with prerenal (67%), renal (24%), or postrenal (9%) suspected AKI. A third had AKIN stage 1 disease, 27% had stage 2 disease, and 40% had stage 3 disease.

Unstimulated saliva was applied to the dipstick to measure whether SUN concentrations were 5-14, 15-24, 25-34, 35-54, 55-74, or 75 or greater mg/dL; BUN was measured concomitantly.

The findings are notable because while AKI in the intensive care unit setting is usually due to acute tubular necrosis, a large proportion of AKI cases outside of the ICU are due to prerenal AKI, which is reversible if diagnosed early and treated aggressively, Dr. Picoits-Filho said.

One way of detecting AKI early on in both the hospital and outpatient settings is by criteria defined by recent consensus: "basically by glomerular filtration rate, but also by urine output," he said.

By using serum creatinine to estimate GFR, you can actually detect patients with AKI. This defines risk for developing more severe AKI (and can help in preventing the need for renal replacement therapy), and also predicts in-hospital mortality, he said.

"The problem is that you need a laboratory facility to get this measurement, and this is not always available, especially in remote areas of the world," he added.

The current findings suggest the SUN dipstick could improve the diagnosis of advanced AKI and aid in triaging patients – particularly in remote areas with limited access to clinical chemistry facilities – and may improve outcomes, he said.

While the test did not prove efficient as a screening tool for chronic kidney disease, it could potentially have a role in monitoring those with chronic kidney disease, he noted.

This study was supported by the Renal Research Institute, New York, and the International Society of Nephrology. Dr. Picoits-Filho reported having no other disclosures.