To the Editor: Researchers studying HIV risks in injecting drug users rarely assess characteristics of injection equipment. Implicit in this omission is the notion that differences in injection equipment have little or no impact on HIV risk. Needles and syringes used by drug injectors may vary in a number of attributes, including syringe volume, type of syringe, and gauge and length of needle. Several observers(1-3) have noted that syringes with detachable needles retain substantially more blood than integral cannula syringes with permanently attached needles and may thus transmit substantially more virus when shared. The bore of a 28-gauge needle is much smaller than the bore of a 25-gauge needle, thus restricting the flow of liquid and increasing the time required to rinse a syringe with a 28-gauge needle. We examined the effect of needle gauge on the minimum time required to disinfect a syringe with bleach...
