ABSTRACT
Objective: To evaluate the performance of the fluorescence assay using albumin blue 580 for microalbuminuria, which is one of the early signs of renal diseases and an important cardiovascular risk factor for patients with diabetes and hypertension. Methods: The fluorescence assay was tested for its precision and reliability by determining the intraassay and interassay coefficients of variation (CV). The correlation of the assay with the standard immunoturbidimetric assay (DCA 2000ฎ microalbumin/creatinine reagent kit), which is one of the methods routinely used for microalbuminuria, was evaluated by quantitating the urinary albumin levels in 13 urine samples by both methods and the results were compared. The fluorescence assay was also used to detect the presence of microalbuminuria in 11 healthy subject, 11 patients with hypertension, and 10 patients with diabetes and hypertension. Results: At the albumin concentrations of 5, 50, and 150 mg/L, the intraassay CVs of the fluorescence assay were 7.9, 4.4, and 3.5%, while the interassay CVs were 4.1, 8.0, and 0.4%, respectively. The fluorescence assay also showed a very good correlation with the standard immunoturbidimetric assay, with the intraclass correlation coefficient of 0.94 (0.81 to 0.98 at 95% confidence interval). When the assay was used to detect the presence of microalbuminuria (the excretion of 30-300 ตg albumin/mg creatinine), it identified two out of 11 patients with hypertension (18%) and three out of 10 patients with both diabetes and hypertension (30%) having microalbuminuria whereas none of the healthy subjects had the condition. In addition, the presence of clinical albuminuria (the excretion of more than 300 ตg albumin/mg creatinine) could also be identified in three patients with hypertension (27%) and one patient with both diabetes and hypertension (10%) respectively. Conclusion: The fluorescence assay using albumin blue 580 was found to be precise and reliable and also showed a very good correlation with the standard immunoturbidimetric assay. In addition, the fluorescence assay is simple and the assay cost is much cheaper compared with the immunoturbidimetric measurement. Therefore, it could be another alternative method for microalbuminuria, particularly for most hypertensive or diabetic patients in Thailand, who can benefit from the detection of microalbuminuria but cannot afford regular tests.