A 50-year-old man comes to the office due to polyuria and polydipsia for the past month. He has smoked a pack of cigarettes daily for the past 30 years. Temperature is 37 C (98.6 F), blood pressure is 150/90 mm Hg, pulse is 75/min, and respirations are 15/min. BMI is 30 kg/m². Physical examination is normal. Serum chemistry panel is as follows: What is the most sensitive test to screen for nephropathy in this patient?

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11ec25c8_d2af_8d5d_bc81_5300a57c06c4_MD0003_00 This patient has elevated random blood glucose (≥200 mg/dL) and subacute symptoms of hyperglycemia (polyuria and polydipsia for 1 month). These factors, along with his age and comorbidities of obesity and hypertension, support a new diagnosis of type 2 diabetes mellitus. Early detection of diabetic nephropathy (DN), a microvascular complication of diabetes and leading cause of end-stage renal disease, is essential to prevent overt kidney disease in patients with diabetes. The diagnosis of DN is made in the setting of persistently (ie, >3 months) elevated levels of albuminuria (>30 mg/g). The random urine albumin-to-creatinine ratio (UACR) is most sensitive for detecting early elevations in albumin excretion; patients with diabetes should be screened with this test at least annually, starting either at diagnosis (for type 2) or 5 years after diagnosis (for type 1). Due to the risk of progression to end-stage renal disease, the presence of moderately increased albuminuria (MIA) (UACR: 30-300 mg/g) warrants prompt therapy with ACE inhibitors (eg, lisinopril), angiotensin receptor blockers (eg, losartan), or sodium-glucose cotransporter-2 inhibitors (eg, canagliflozin). (Choice A) Creatinine clearance can change over the DN disease course but is an unreliable and insensitive screening tool compared with UACR testing. For example, although creatinine clearance can be elevated in early DN (due to glomerular hyperfiltration), it can also be normal even in the setting of MIA. (Choice B) Although dipstick testing of protein detects proteinuria, it is insensitive to low levels of albumin (ie, those diagnostic of MIA). Moreover, results can vary depending on urine concentration. Therefore, the UACR test is a superior approach to screening for early DN. (Choice C) Oral glucose tolerance testing can be used to diagnose gestational diabetes but has no role in screening patients for DN. (Choice D) Early DN is not associated with visible changes in ultrasonography; a change in kidney size is primarily expected in advanced renal failure. Therefore, renal ultrasound is a suboptimal DN screening tool. Educational objective: Diabetic nephropathy, a microvascular complication of diabetes mellitus, is associated with abnormal (moderately increased) albuminuria. Random urine albumin-to-creatinine ratio testing is the most sensitive test to detect early elevations in albumin excretion. This test should be performed at least annually in patients with type 2 diabetes mellitus starting at diagnosis.

A 50-Year-Old Man Comes to the Office Due to Polyuria