Estimated Total Albumin in Fresh Urine Samples Based on Correlation Between the Roche Immunoturbidimetric and an In-House HPLC Method
Abstrakt
Background: Many studies have reported higher values of urinary albumin measured by high performance liquid chromatography (HPLC) in comparison with immunochemical methods. The aims of our study were the implementation of the HPLC method for albuminuria, testing the hypothesis about coeluting proteins, comparison of albuminuria assessed by HPLC and immunoturbidimetric (IT) methods in diabetic and non-diabetic patient samples.
Methods: We compared albuminuria assessed by HPLC with albuminuria assessed by the IT method in fresh urine samples of 636 diabetics and 456 non-diabetics. We investigated relationships between albuminuria and blood glycated hemoglobin HbA(1c).
Results: We found significant differences between the parameters of linear regressions between albuminuria determined using HPLC and IT among patients with and without DM, and even between patients with DM type 1 and type 2. We confirmed the underestimation of albuminuria assessed by IT.
We did not reveal any significant correlation between blood glycated hemoglobin and any of the parameters derived from albuminuria. Conclusions: We excluded non-specificity of the HPLC method.
Despite of a little bit lower analytical sensitivity of the HPLC method in comparison with IT method the diagnostic sensitivity of HPLC method is higher, because it measures the total albuminuria (immunoreactive plus immuno-unreactive). We developed three formulas (for nondiabetics, for diabetics type 1 and diabetics type 2) for the estimation of the total albuminuria from IT values.
We also confirmed that albuminuria and HbA(1c) are independent biomarkers.