Heparin interference in the cerebrospinal fluid protein assay measured with a pyrogallol red-molybdate complex.

BACKGROUND: Increased cerebrospinal fluid (CSF) total protein is a useful indicator of meningeal or central nervous system disease. Occasionally the primary care physicians added heparin to CSF samples to avoid clotting. The aim of this study is to investigate the interference of heparin on CSF total protein measurement. METHODS: CSF specimens were collected from 230 in-patients with various diseases and analyzed by the Vitros 950 PROT slide and the Toshiba TBA-120FR assay. After adding 0, 0.0625, 0.25, 0.5, 0.75, 1, 2 and 4 IU/ml of heparin that was diluted in 20 microl of normal saline to 180 microl of CSF aliquots, CSF total protein concentrations were determined again by the 2 assay systems in the absence or presence of protamine. RESULTS: At low (<40 mg/dl) and mildly increased (40-or<100 mg/dl) CSF total protein, the measured protein concentrations significantly decreased up to 91% when 4 IU/ml of heparin was added to the samples before being analyzed by the Toshiba TBA-120FR assay. At moderately increased (100-or<200 mg/dl) and high (>or=200 mg/dl) CSF total protein, 62% and 27% decreases were found, respectively. Only 1-8% decline was found when 4 IU/ml of heparin was added to the samples before being analyzed by the Vitros 950 PROT assay. Addition of protamine partially reversed the interference of heparin. CONCLUSIONS: The interference of heparin in the CSF total protein assay is dependent on the reaction principle, especially when the CSF total protein level is normal to mildly elevated.

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.