Residual Negative Pressure in Vacuum Blood-Collection Tube and Hemolysis in Pediatric Blood Specimens.

OBJECTIVE: To determine a method to reduce specimen hemolysis rates in pediatric blood specimens. METHODS: A total of 290 blood specimens from pediatric patients were classified into the capped group or uncapped group. The hemolysis index and levels of lactate dehydrogenase (LDH) were measured using an automated biochemical analyzer. Also, we performed a paired test to measure the concentration of free hemoglobin in specimens from 25 randomly selected healthy adult volunteers, using a direct spectrophotometric technique. RESULTS: The hemolytic rate of capped specimens was 2-fold higher than that of uncapped specimens. We found significant differences for LDH. Also, there was a significant difference in the concentration of free hemoglobin in the random-volunteers test. CONCLUSIONS: Eliminating the residual negative pressure of vacuum blood-collection tubes was effective at reducing the macrohemolysis and/or microhemolysis rate.

Residual Negative Pressure in Vacuum Tubes Might Increase the Risk of Spurious Hemolysis.

BACKGROUND: We planned a study to establish whether spurious hemolysis may occur when negative pressure remains in vacuum tubes. METHODS: Four tubes with different vacuum levels (-54, -65, -74, and -86 kPa) were used to examine blood drawn from one healthy volunteer; the tubes were allowed to stand for different times (1, 2, 3, and 4 hours). The plasma was separated and immediately tested for free hemoglobin (FHb). Thirty patients were enrolled in a verification experiment. RESULTS: The degree of hemolysis observed was greater when the remaining negative pressure was higher. Significant differences were recorded in the verification experiment. CONCLUSIONS: The results suggest that residual negative pressure might increase the risk of spurious hemolysis.