Comparison of three automated urinalysis systems--Bayer Clinitek Atlas, Roche Urisys 2400 and Arkray Aution Max for testing urine chemistry and detection of bacteriuria.

BACKGROUND: Our study is aimed to determine the performance of 3 automated urinalysis systems-Clinitek Atlas, Urisys 2400 and Aution Max. METHODS: One thousand urine specimens were analyzed with the 3 automated systems. The results of the 3 assays were compared for testing urine chemistry and evaluating the capacity of leukocyte esterase and nitrite to detect bacteriuria. RESULTS: The correlation between the 3 instruments represented as within 1 grading difference was better between the Atlas and Aution Max systems for pH, blood, glucose, urobilinogen, ketone and specific gravity. For protein and nitrite, better correlation was observed between the Atlas and Urisys 2400, while the Aution Max and Urisys 2400 conveyed better correlation for bilirubin and white blood cells. The sensitivity and specificity of both the leukocyte esterase and nitrite in screening for significant bacteriuria were 71.7, 58.9, 70.8% and 99.1, 99.1 and 97.2%, for the Clinitek Atlas, Aution Max and Urisys 2400, respectively. CONCLUSIONS: The automated urinalysis systems demonstrate acceptable correlations with each other in urine chemistries, especially between the Clinitek Atlas and Aution Max systems on the majority of items. The specificity and negative predictive value of leukocyte esterase and nitrite of the 3 instruments for screening of significant bacteriuria were sufficient to avoid unnecessary urine culture.

Interference caused by the contents of serum separator tubes in the Vitros CRP assay.

BACKGROUND: We have observed discrepancies between C-reactive protein (CRP) measured in serum prepared from a serum separator tube (SST) and that obtained from a plain tube, when using the Vitros CRP assay. Our study aimed at elucidating the cause of these discrepancies. METHODS: Eighty-seven specimens from hospitalized patients with various types of inflammatory disease were analysed using a fixed-point immuno-rate method on a Vitros CRP slide. The serum was prepared simultaneously in both vacuum and SSTs. We also performed mixing tests by adding 47 samples of serum prepared from plain tubes to SSTs and incubating for 15 min before CRP analysis. RESULTS: Lower values of CRP were found in serum prepared from plain tubes than in serum from SSTs. Addition of serum prepared from plain tubes to SSTs and incubating for 15 min increased the CRP values significantly. The ratio of CRP measured in serum prepared from plain tubes and from SSTs did not differ significantly from the ratio obtained when serum was prepared in a plain tube then added to an SST. DISCUSSION: We propose that SSTs can adsorb some macromolecules that form complexes with CRP. The addition of SST gel to serum results in the release of CRP molecules from these complexes, which enhances the antigen-antibody reaction on the Vitros CRP slide and increases the measured CRP concentrations.