MKSAP Quiz: managing risk factors
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A 59-year-old woman with a history of coronary artery disease comes for a routine physical examination. She is asymptomatic. One year ago, she underwent placement of a drug-eluting stent in the right coronary artery. She also has hypertension and dyslipidemia. Average home blood pressure measurement is 125/80 mm Hg. Medications are clopidogrel, metoprolol, simvastatin, and low-dose aspirin.
On physical examination, vital signs are normal except for a blood pressure of 135/82 mm Hg in both arms. BMI is 32. The remainder of the physical examination is normal.
Laboratory studies:
Which of the following diagnostic studies should be performed next in this patient?
A. 24-hour urine collection for protein
B. Kidney ultrasonography
C. Spot urine albumin-creatinine ratio
D. No further studies at this time
MKSAP Answer and Critique
The correct answer is C) Spot urine albumin-creatinine ratio. This item is available to MKSAP 15 subscribers as item 40 in the Nephrology module.
The most appropriate study for this patient is a spot urine albumin-creatinine ratio. This patient has risk factors for chronic kidney disease (CKD), including coronary artery disease, hyperlipidemia, and hypertension. The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (NKF K/DOQI) clinical practice guidelines recommend that patients at risk for CKD undergo screening with urinalysis, serum creatinine measurement, and estimation of the glomerular filtration rate (GFR) using the Modification of Diet in Renal Disease (MDRD) study equation in order to classify the stage of CKD. This equation is most accurate for estimating the GFR in patients with an estimated GFR below 60 mL/min/1.73 m2. Measurement of the albumin- or protein-creatinine ratio using a first morning void urine sample would help to determine the protein- or albumin-creatinine ratio, which would be sufficient to document proteinuria.
Although rarely clinically indicated, a 24-hour urine collection for creatinine clearance is recommended to estimate the GFR in patients with a normal or near-normal GFR. However, mathematical equations to estimate the GFR generally are preferred over 24-hour urine collection, which is cumbersome and often inaccurate.
Kidney ultrasonography is recommended in patients with CKD to evaluate for structural abnormalities. However, performing this study would be premature until a diagnosis of CKD is established.
Key Point
- Patients with risk factors for chronic kidney disease should undergo screening with urinalysis, serum creatinine measurement, first morning void random urine protein- or albumin-creatinine ratio, and estimation of the glomerular filtration rate (GFR) using the Modification of Diet in Renal Disease (MDRD) study equation when the estimated GFR is below 60 mL/min/1.73 m2.