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.

Adhesion of staphylococci to polymers with and without immobilized heparin in cerebrospinal fluid.

Infections of cerebrospinal fluid (CSF) shunts constitute a serious clinical problem. The role of adhesion by coagulase negative staphylococci, the most common etiological agent, was examined in vitro to polyvinyl chloride (PVC), silicone, and to PVC and silicone with end-point attached (EPA) heparin. These are flexible materials commonly used in neurosurgical implants. Bacterial adhesion was quantitated by bioluminescence. The bacterial adhesion to biomaterial surfaces increased with increasing concentrations of bacterial cells. Scatchard plot analysis showed continuous negative (concave) slopes, indicating multiple interactions between biomaterial and bacteria. The thermodynamic studies showed a positive value of the standard entropy change at 37 degrees C, which indicates that hydrophobic interactions are important in bacterial adhesion to polymers. Incubation with CSF for 1 h decreased bacterial adhesion in 75% of the samples compared to incubation in buffer. Thus, the contribution of CSF proteins, like fibronectin, for the initial bacterial adhesion might be small. Heparinization of silicone and PVC decreased the numbers of adhered bacteria by 23 to 54% and 0 to 43% compared to unheparinized surfaces. Among putative inhibitors tested, suramin, chondroitin sulfate, and fucoidan inhibited adhesion to 81 +/- 19, 78 +/- 22, and 64 +/- 7%, respectively. These findings indicate that hydrophobic interactions play an important role, and heparinization rendering the biomaterial surface hydrophilic is therefore effective to reduce bacterial adhesion. Heparinized polymers incubated with putative inhibitors may be the optimal way to prevent shunt infections.