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CASE 5.1

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A 49-year-old, female with a 5-year history of diabetes mellitus type 2, presents for an initial visit. She has no known complications of diabetes. She takes metformin, glyburide, and aspirin. On examination, you find a pleasant, obese female in no distress. Her blood pressure is 136/86 mm Hg. As you discuss monitoring her diabetes, you recommend screening for early kidney disease.

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Question 5.1.1 Which of the following approaches is the recommended way to screen for diabetic kidney disease?

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A) Obtain a 24-hour urine collection for albumin now and again in 3 years.

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B) Obtain a spot urine albumin every year.

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C) Obtain a spot urine albumin/creatinine ratio every year.

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D) Obtain a urinalysis every year.

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E) Obtain a serum creatinine every year.

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Answer 5.1.1 The correct answer is "C." Moderately increased albuminuria (previously known by the misnomer "microalbuminuria") is a marker for increased risk of future kidney disease in diabetic patients. The best test to evaluate for moderately increased albuminuria is the urine albumin/creatinine ratio. Its advantages include ease of use, relatively low cost, and good correlation with 24-hour urine collections. Some of you may have chosen "B." A "spot microalbumin" (now a spot albumin) is a common but less accurate way to provide screening and may still be in use in some areas. As a practical matter, many physicians use urine albumin alone as a method of screening, but this method does not allow for corrections for variations in urine volume and dilution. A random spot urine albumin/creatinine ratio is normally less than 30 mg/g. Values above 30 mg/g are consistent with 24-hour measures showing abnormal amounts of albumin. Answers "D" and "E" offer measures of kidney function that simply are not sensitive enough to use for screening purposes.

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Note on terminology. The term "microalbuminuria" has been replaced with "moderately increased albuminuria," but the definition remains the same (30–300 mg protein in the urine per 24 hours). Compare this to "severely increased albuminuria," defined as greater than 300 mg of protein in the urine per 24 hours.

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Question 5.1.2 Her albumin/creatinine ratio is 42 mg/g. The next step to confirm moderately increased albuminuria is:

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A) Repeat urine albumin/creatinine ratio.

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B) Urine dipstick for protein.

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C) 24-hour urine collection for total protein excretion.

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D) Serum creatinine.

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E) Referral to a nephrologist.

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Answer 5.1.2 The correct answer is "A." Verification by repeat urine ...

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