Screening for Microalbuminuria in Ghanaian Diabetic Patients: Albumin Blue 580 Fluorescence Probe Evaluated

Abstract

The Albumin Blue 580 fluorescent dye was evaluated for the measurement of urine albumin content. The calibration of the assay was linear up to 150.0mg/L with a minimum detection limit of 1.4mg/L. The intraassay CV was 4.3 %( 14.5mg/L), 3.7 %( 50.2mg/L) and 1.4 %( 100.0mg/L), interassay CV was 2.7%, 2.6% and 3.7% for the respective urine albumin concentrations. Recovery of added albumin to urine was 95-112%, reproducibility for 9 replicate analysis of 3 urine samples was 8.2 %( 6.0mg/L), 4.6 %( 62.4mg/L) and 4.9 %( 130.2mg/L). Storage at -20°C and -80°C beyond 14 days may misclassify borderline cases of normoalbuminuria and microalbuminuria. In the non-communicable disease survey aliquots of 2hour albustix negative urine were obtained from 47 newly diagnosed diabetic subjects, 52 non-diabetic and non-hypertensive subjects as a control group. The age, systolic blood pressure, diastolic blood pressure and AER were significantly lower in the control subjects (p<0.05 (38.7 ± 8.6 vrs 47.3 + 9.0 yrs;), (119.1 ±10.1 vrs 137.3 ± 22 mmHg); (77.7 ± 7.5 vrs 88.6 ± 13.0 mmHg) and (11.6 ± 1.9 vrs 34.6 ± 2.1/μg/min) respectively. 40 (85.1%) and 7 (13%) of diabetic and non-diabetic subjects respectively had AER ≥20.0 μg/min. There were 7 proposals of UAC cut off values in predicting overnight AER of ≥15.0 μg/min and ≥ 20.0 μg/min. Proposal VI with UAC of 25.0mg/L in predicting overnight AER ≥20.0 μg/min had a diagnostic sensitivity of 100% for the newly diagnosed diabetic subjects and specificity of 87% in the nondiabetic subjects for the absence of microalbuminuria and a positive predictive value of 97.5%. At a lower UAC of 10.0mg/L sensitivity was 100% for both groups but the specificity reduced to 32% and 16.7% for diabetic and non- diabetic subjects respectively. The prevalence of elevated N-AER in 212 diabetic patients providing a single 12hour overnight urine collection was 37.7%. The diagnostic accuracy, Likelihood ratio of a positive test result within this population and the post-test probability were 92%, 7.7 and 82.5% respectively, making the AB 580 assay method a useful and a reliable test for the screening and diagnosis of early diabetic kidney disease in Ghanaian diabetic subjects and for evaluation of risk factors for the progression of intermittent to persistent microalbuminuria.