الفهرس 
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Abstract
Urinary albumin has different antigenic sites so antibodies from different manufacturers could react with these sites and this leads to the lack of a reference material for urinary albumin that covers all its antigenic sites.
All quantitative laboratory methods for measuring urinary albumin are immunoassays, including Radioimmunoassay (RIA), Enzyme-Linked Immunosorbent Assay (ELISA), Nephelometry, Immunoturbidimetry and Chemiluminescence immunoassay (CLIA).
Medical laboratories should perform regular method comparisons between the methods used to measure urinary albumin. There are few published comparative studies between the methods that measure urinary albumin, which make it a good field to study.
The present study was conducted on two methods for measuring urinary albumin (Immunoturbidimetry and Chemiluminescence methods). The study included two phases, method verification and method comparison. The studied methods were verified by testing the precision (repeatability and reproducibility), accuracy, analytical sensitivity and verification of reference intervals.
As regard the precision (repeatability and reproducibility), the CV% of both methods were within Westgard desirable specification for imprecision.
In repeatability study, the low sample of Chemiluminescence method showed a better CV% than that in Immunoturbidimetry method (5.78 % 11.32 % respectively) while in high sample the CV% was better in Immunoturbidimetry method (0.733 %, 9.43 % respectively).
In reproducibility study, the low sample, high sample and quality control of Chemiluminescence method showed a better CV% (12.16 %, 13.1 %, 7.7 %, 10.6 % respectively) than that in Immunoturbidimetry method (16.7%, 14.8 %, 11.9 % respectively).
Regarding the accuracy, the mean % recovery of Immunoturbidimetry method was better than that of Chemiluminescence method (104%, 122% respectively). On drawing a regression line it was found that the agreement between the observed and expected results of Immunoturbidimetry method was better than that of Chemiluminescence method (R Sq Linear=1, 0.992 respectively).
The calculated bias % and TE % of both methods were within Westgard desirable specification for inaccuracy but the bias % of Immunoturbidimetry method was lower than that of Chemiluminescence method (7.393%., 14.79% respectively) while the calculated TE % of both methods were comparable to each other’s.
Analytical measuring range (AMR) of Immunoturbidimetry method (0.9-130 mg/l (verified between 0.9-106 mg/l)) was better than that of Chemiluminescence method (2.5-60 mg/l (verified between 2.5-53 mg/l)).
The reference intervals of both methods were verified according to CLSI guidelines for Defining, Establishing and Verifying Reference Intervals in the Clinical Laboratory.
On comparing the results of 108 urinary samples measured by the two methods using Wilcoxon Signed Ranks Test, (p-value: 0.103), Bland Altman Plot (p-value: 0.787) and MC-nemar test (p-value: 0.996), it was found that there was no significant difference between the two methods, so one method can be used in replace of the other.
Regression line analysis showed a significant strong positive correlation between the two methods with 91% agreement (for 95% CI). (P-value: <0.001, R Sq Linear: 0.91)
On dividing the samples into those < 30 mg/l and those > 30 mg/l, it was found that there was no significant difference between the two methods on the two levels (P-value: <0.001) but the agreement between the two methods in samples < 30 mg/l was better than that in samples > 30 mg/l. (R Sq Linear: 0.96, 0.86 respectively)
from the present study the following could be concluded
There is no significant difference between Immunoturbidimetry and Chemiluminescence methods in measuring urinary albumin but Immunoturbidimetry method is better than Chemiluminescence method as regard accuracy and analytical measuring range. This is added to the fact that Immunoturbidimetry method is a cheaper and more available so it is more convenient to be used as a routine method for measuring urinary albumin