Double-Knot Blood Bag Closure May Reduce Contamination Risk in Low-Resource Settings

Use of a simple, double-knot technique to seal blood bags may reduce the risk of bacterial contamination in resource-limited settings, according to a correspondence published recently in the New England Journal of Medicine.

Bacterial contamination of blood products remains a significant transfusion safety concern, particularly in low-income countries where blood collection facilities may lack access to heat-sealing equipment commonly used in higher-resource settings. According to the authors, blood donation services in Nigeria and many countries in sub-Saharan Africa routinely use a single-knot method to close blood-bag tubing.

To evaluate whether an additional knot could reduce contamination risk, investigators conducted a controlled laboratory study using 180 pediatric blood bags filled with culture medium. Half of the bags were sealed with a single knot and half with a double knot. Researchers then exposed the tubing to high concentrations of bacteria, including Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli, and stored the bags at room temperature for 35 days.

Testing identified bacterial contamination in 8 of 90 blood bags sealed with a single knot (9%), while none of the bags sealed with a double knot showed contamination. Because the study used a high-stress test involving prolonged exposure to concentrated bacteria, the authors noted that contamination of refrigerated blood bags sealed with a double knot would be unlikely under standard storage conditions.

The authors said the findings support double-knot closure as a simple, low-cost intervention that could improve transfusion safety in settings where alternatives such as heat-sealing equipment or metal clamps are unavailable or unaffordable.