Screening for Microalbuminuria in Ghanaian Diabetic Patients: Albumin Blue 580 Fluorescence Probe Evaluated
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Date
2000-07
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University of Ghana
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.