American Association for Clinical Chemistry
Better health through laboratory medicine
Heads Up: June 26, 2008

Sensitivity and Specificity of a Single Emergency Department Measurement of Urinary Neutrophil Gelatinase-Associated Lipocalin for Diagnosing Acute Kidney Injury

Acute kidney injury is a common complication among ambulatory and hospitalized patients and its incidence has increased in recent years. It is important to be able to distinguish acute kidney injury from other forms of renal disease to rapidly manage associated illness. New research published in the Annals of Internal Medicine show that assessing urinary NGAL (neutrophil gelatinase-associated lipocalin) can help clinicians discriminate acute from other forms of kidney disease. In their study, scientists at Columbia University Medical Center (New York, N.Y.) tracked kidney function and compared measurements of kidney disease biomarkers in 635 emergency room patients. They observed that patients with acute kidney injury had markedly elevated mean urinary NGAL compared to patients with other forms of kidney dysfunction. They found that NGAL level was highly predictive of clinical outcomes, including nephrology consultation, dialysis, and ICU admission.

Cardiac Troponin and Outcome in Acute Heart Failure

In patients with acute decompensated heart failure, troponin levels may identify those most at risk for dying in the hospital, according to a retrospective registry study published in the New England Journal of Medicine. Troponins had been measured as part of routine care in about 80% of the more than 105,000 hospitalized patients in the Acute Decompensated Heart Failure (ADHERE) national registry. Of those, 67,924 met the entry criteria for creatinine; 4,240 of them, or about 6.2%, were positive for troponin, defined as any elevation up to the prospectively defined cutoffs of 1.0 µg/L for troponin I and 0.1 µg/L for troponin T. In-hospital mortality for troponin-positive and -negative patients was 8.0% and 2.7%, respectively; those who had elevated levels of either form of troponin were more than twice as likely to die in the hospital compared with those who tested negative for the protein. Mortality also rose with troponin concentrations—the adjusted odds ratio for death for patients with troponin I concentrations in the top quartile, compared with the lowest quartile, was 2.33.

The Diagnosis of Cushing’s Syndrome: An Endocrine Society Clinical Practice Guideline

The Endocrine Society has released new clinical practice guidelines for diagnosing Cushing’s syndrome. The guidelines were published in the Journal of Clinical Endocrinology & Metabolism. After excluding steroid medications, the guidelines suggest testing for Cushing’s syndrome in patients with multiple and progressive features compatible with the condition, particularly those with a high discriminatory value. The guidelines recommend testing for the condition in patients who have unusual features for their age (such as osteoporosis or hypertension); patients with multiple and progressive features such as easy bruising, facial plethora, proximal myopathy, and striae; children with decreasing height percentile and increasing weight; and patients with adrenal incidentaloma. They also suggest initial use of one test with high diagnostic accuracy (urine cortisol, late night salivary cortisol, 1-mg overnight or 2-mg 48-h dexamethasone suppression test). The guidelines also suggest certain tests, such as urinary 17-ketosteroids or insulin tolerance test, should not be used to test for Cushing’s syndrome. A patient who has an abnormal result should see an endocrinologist and undergo a second test.