Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 67-year-old man is evaluated following a recent diagnosis of type 2 diabetes mellitus.

On physical examination, blood pressure is 134/84 mm Hg; other vital signs are normal. BMI is 30. The remainder of the examination is unremarkable.

Laboratory studies show an HbA1c of 7.8%, blood urea nitrogen 15 mg/dL (5.4 mmol/L), and serum creatinine 1.0 mg/dL (88.4 µmol/L). Urinalysis shows no protein, 3+ glucose, 0-2 erythrocytes/hpf, and 0-3 leukocytes/hpf.

In addition to therapeutic lifestyle changes, which of the following is the most appropriate next step in management?

A. Estimated glomerular filtration rate using the Modification of Diet in Renal Disease study equation
B. Urine albumin–creatinine ratio in 5 years
C. Urine albumin–creatinine ratio now
D. Urine protein–creatinine ratio in 5 years
E. Urine protein–creatinine ratio now

MKSAP Answer and Critique

The correct answer is C. Urine albumin–creatinine ratio now.

A urine albumin–creatinine ratio now is indicated to screen for diabetic nephropathy in this patient with newly diagnosed type 2 diabetes mellitus. Diabetic nephropathy is the most common glomerular disease and develops in approximately 35% of patients with type 1 and 2 diabetes. The American Diabetes Association guidelines specifically recommend annual measurement of the urine albumin excretion for patients who have had type 1 diabetes for 5 years or more and for all patients with type 2 diabetes beginning at the time of diagnosis. Screening for microalbuminuria usually involves obtaining a urine albumin–creatinine ratio on a first morning void urine sample, a random sample, or a timed urine collection. Microalbuminuria is confirmed when two of three samples obtained within a 6-month period reveal a urine albumin–creatinine ratio between 30 and 300 mg/g. Microalbuminuria is the first easily detectable sign of diabetic nephropathy and usually occurs 5 to 15 years after the diagnosis of diabetes. Approximately 10 to 15 years after the diagnosis of diabetes, macroalbuminuria (urine albumin–creatinine ratio above 300 mg/g) can be detected on urine dipstick and is accompanied by decreasing kidney function and increased blood pressure. Preventive measures in managing microalbuminuria include early initiation of an ACE inhibitor and/or angiotensin receptor blocker, adequate blood pressure control, blood glucose and lipid control, and smoking cessation, which reduce the risk of end-stage kidney disease and cardiovascular events.

The Modification of Diet in Renal Disease (MDRD) study equation was developed for patients with chronic kidney disease and has not been shown to accurately estimate kidney function in healthy persons or in diabetic patients with preserved glomerular filtration.

Waiting 5 years to screen for microalbuminuria is not appropriate in patients with type 2 diabetes because many patients may have diabetes for years before diagnosis, and earlier onset of diabetic nephropathy and faster progression of its clinical stages are common compared with type 1 diabetes.

The urine protein–creatinine ratio can be used in patients with overt proteinuria or later stages of diabetic nephropathy, neither of which is seen in this patient at this time

Key Point

• A urine albumin–creatinine ratio is indicated to screen for diabetic nephropathy in patients with newly diagnosed type 2 diabetes mellitus.

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