Microalbumin: Creatinine Ratio, Random Urine

Microalbumin: Creantinine Ration, Random Urine

CPT Test code: 82043;82570

Test Includes: Microalbumin, random urine; creatinine; albumin:creatinine ratio
Related Information:
Specimen: Urine (random)
Volume: 10 mL
Minimum Volume: 2 mL (Note: This volume does not allow for repeat testing.)
Container: Plastic urine container
Collection: Collect random urine without preservatives. pH must be 4-8.
Storage Instructions: Refrigerate
Causes for Rejection: Bloody specimen
Reference Interval: • Normal: 0-30 mg/g creatinine

• Microalbuminuria: 30-300 mg/g creatinine

• Clinical albuminuria: >300 mg/g creatinine

Use: Measurement of albumin levels in urine below the detection level of urine dipsticks. This test is useful in the management of patients with relatively early diabetes mellitus to assist in avoiding or delaying the onset of diabetic renal disease.
Limitations: Because of the inherent day-to-day variability of albumin excretion into the urine, two of three microalbumin levels measured within a three- to six-month period should be abnormal before considering a patient to have crossed a diagnostic threshold.1 Physical exercise during the previous 24 hours can cause a transient elevation in microalbumin. Other variables, including infection, fever, congestive heart failure, marked hyperglycemia, and marked hypertension, can result in increased microalbumin levels.
Additional Information: Albumin accounts for approximately 50% of the protein in plasma.2 The kidney works to prevent the loss of albumin into the urine through active resorption, but a small amount of albumin can be measured in urine of individuals with normal renal function. Microalbumin is the term ascribed to the measurement of albumin in urine at concentrations below the sensitivity of dipstick tests for total protein. Microalbuminuria (ie, urine albumin levels above the reference range and below the level of clinical albuminuria) is a important indicator of deteriorating renal function.

The prognostic value of consistently elevated microalbumin levels is particularly well established in diabetic patients.1 Renal disease is a common microvascular complication of diabetes. Without specific interventions, 80% of type I diabetics with repeatedly elevated microalbumin levels will go on to end-stage renal disease. Twenty percent to 40% of type II diabetics with sustained microalbuminuria will progress to overt nephropathy.

The American Diabetes Association (ADA) recommends that routine urinalysis be performed annually on adults with diabetes.1 If the urinalysis is negative for protein, microalbumin measurement is recommended. The ADA also recommends annual screening of children beginning at puberty or after five years of disease duration. The reference intervals stated above reflect the diagnostic criteria prescribed by the ADA.1

Footnotes: 1. American Diabetes Association, “Position Statement: Diabetic Nephropathy,” Diabetes Care, 1997, 20(50):S24-S27.

2. Sacks DB, “Carbohydrates,” Tietz Textbook of Clinical Chemistry, 3rd ed, Burtis CA, Ashwood ER, eds, Philadelphia, PA: WB Saunders Co, 1999, 750-808.

References: Metcalf P, Baker J, Scott A, et al, “Albuminuria in People at Least 40 Years Old: Effect of Obesity, Hypertension, and Hyperlipidemia,” Clin Chem, 1992, 38(9):1802-8.PubMed 1526018