Point-of-care screening for diabetic ketoacidosis

Diabetic ketoacidosis (DKA), a common acute and potentially life-threatening complication of diabetes that results from insulin deficiency, is characterized by raised blood glucose (hyperglycemia) and metabolic acidosis. Metabolic acidosis occurs due to abnormal accumulation in blood of ketoacids, principally ß-hydroxybutyric acid and acetoacetic acid. 

In an emergency care setting it is common practice to screen all patients with hyperglycemia for DKA using urine dipstick testing for the presence of ketones (i.e. the two ketoacids and acetone, a metabolite of acetoacetic acid). An alternative approach is now available, made possible by the development of point-of-care analyzers that allow rapid (within 1 minute) estimation of serum ß-hydroxybutyrate concentration from a drop of venous blood. 

The latest of several studies comparing the reliability of traditional urine dipstick testing with that of the newer point-of-care blood testing to diagnose DKA is recently published. The study population comprised 516 patients who on routine triage testing following admission to the emergency department of a Californian hospital were found to have blood glucose in excess of 250 mg/dL (13.9 mmol/L). 

All were submitted for DKA screening using both urine dipstick testing for ketones and point-of-care blood measurement of serum ß-hydroxybutyrate concentration. A diagnosis of DKA was ultimately confirmed in 54 of the 516 hyperglycemic patients. Urine dipstick testing for ketones was positive in 53 of the 54 patients with DKA (sensitivity 98.1 %) but was also positive in 300 of the 462 patients without DKA (specificity 35.1 %). 

Using a manufacturer’s suggested cut-off, ß-hydroxybutyrate concentration of >1.5 mmol/L, the point-of-care blood testing method was positive in 53 of the 54 patients with DKA, but only 99 of the 462 patients without DKA (specificity 78.6 %). 

The authors were able to conclude that the two methods are equally sensitive in detecting DKA, but that urine testing is associated with a significantly greater number of false positive results. Clearly, fewer patients would be needlessly submitted for further investigation of possible DKA if the point-of-care blood test is used to screen for the condition than if urine dipstick testing is the screening tool.