URINARY ALBUMIN EXCRETION RATE DERIVATION FROM ALBUMIN/CREATININE RATIO

Vijay Viswanathan,C.Snehlatha, B. Mamtha Nair,A. Ramachandran, Diabetes Research Centre, Chennai.

Aim: To determine the validity of derivation of albumin excretion rate (AER) from albumin to creatinine ratio (A/C).

Subjects and methods:  Albumin excretion was determined in 24 hour urine samples and 115 Type 2 diabetic subject with albuminuria < 300mg/day were selected for the study.  Albuminuria per day was determined by immunoturbidimetry and was used as the reference method for further calculations.  In the same samples A/C (mg of albumin /mg of creatinine) and AER (mgof albumin/minute ) were estimated.  The correlation between the A/C ratio and the AER was determined using Pearson’s Linear Correlation method.  The regression equation for deriving AER from A/C ratio and the specificity and sensitivity of AER and A/C ratio for detection of microalbuminuria (MAU) (Albuminuria 30-300mg/day)  were calculated.

Results:  The correlation between A/C and AER was significant (r=0.91, P<0.0001).  The regression equation was AER=0.34 + 0.6xA/C ratio.  The sensitivity of A/C to detect MAU was 95% (37/39 MAU) and the specificity was 89%.  The sensitivity of AER derived from A/C was 100% and the specificity was 99%.

Conclusion:  It was observed that AER derived from A/C ratio had a good correlation with the A/C ratio and it also showed 100% sensitivity and specificity for MAU.   These findings indicate that the calculation of AER from A/C ratio is a valid procedure and can avoid cumbersome 24 hour urine collections.