Underestimation of urinary albumin to creatinine ratio in morbidly obese subjects due to high urinary creatinine excretion.
OBJECTIVE
Albuminuria, a chronic kidney and/or cardiovascular disease biomarker, is currently measured as albumin-to-creatinine ratio (ACR). We hypothesize that in severely obese individuals ACR might be abnormally low in spite of relatively high levels of urinary albumin due to increased creatininuria.


METHODS
One-hundred-eighty-four subjects were divided into tertiles based on their BMI. Fat-free mass (FFM) and fat-mass were assessed by DEXA; 24-h creatinine and albumin excretion, ACR, lipid profile and blood pressure were measured.


RESULTS
Twenty-four-hour creatinine highly correlated (R = 0.75) with FFM. Since both creatininuria and albuminuria increased with the BMI, being the increase in creatininuria preponderant in subjects with BMI>35, their ratio (AC-ratio) did not change significantly from that of subjects in the lower BMI tertile. ACR only correlated with the systolic blood pressure, while both albuminuria and cretininuria correlated (P = 0.01) with the absolute 10-year CHD risk. In subjects with BMI>35, 100 mg of albumin excreted with urine increased the CHD risk of 2%.


CONCLUSIONS
Albumin-to-creatinine ratio is underestimated in severely obese individuals as a consequence of the large creatininuria, which is proportional to the increased FFM. Therefore, at least in this population 24-h albuminuria should be more reliable than ACR.
Department of Internal Medicine, Catholic University, Largo A. Gemelli 8, 00168 Rome, Italy.
Caterina
C
Guidone
Donatella
D
Gniuli
Lidia
L
Castagneto-Gissey
Laura
L
Leccesi
Eugenio
E
Arrighi
Amerigo
A
Iaconelli
Geltrude
G
Mingrone
D000328:Adult; D000418:Albumins / Q000032:analysis*; D000419:Albuminuria / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D001786:Blood Glucose / Q000032:analysis; D001794:Blood Pressure; D001823:Body Composition; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000503:physiopathology; D003404:Creatinine / Q000652:urine*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009017:Morbidity; D009765:Obesity / Q000503:physiopathology / Q000652:urine*; D012307:Risk Factors; D013048:Specimen Handling
D000418:Albumins; D015415:Biomarkers; D001786:Blood Glucose; D003404:Creatinine