Study shows efficacy of bar-code usage

Bar-coding can reduce errors, study says

A new study published in the Annals of Internal Medicine1 indicates that the use of bar code technology in a hospital pharmacy can help achieve significant reductions in medication errors and potential adverse drug events (ADEs). However, the authors add, some systems are more effective than others.

The research team used three different configurations, notes Eric Poon, MD, MPH, assistant professor of medicine at Harvard Medical School and associate physician at the Brigham & Women's Hospital, both in Boston, MA.

"There were three different ways of dispensing meds in the pharmacy, so depending on where the meds were going and what types of meds you're talking about, there were three different possibilities with bar-code technology," he explains.

In two configurations, all doses were scanned once during the dispensing process. In the third configuration, only one dose was scanned if several doses of the same medication were being dispensed.

"In two of the three systems, every single dose is scanned at least once during the process, but in one of the three that does not necessarily happen," says Poon. "In the two in which every single dose gets scanned, we verified there was an 80%-90% reduction in the incidence of dispensing errors and also in potential ADEs."

The researchers were not able to assess actual ADEs, Poon continues, "Because errors were actually stopped from getting out. But what we did see with the two good processes was anywhere from an 86% to 97% reduction in potential ADEs — which was pretty good."

The numbers up close

In the pre- and post-bar code implementation periods, the authors observed 115,164 and 253,984 dispensed medication doses, respectively. Overall, the rates of target potential ADEs and all potential ADEs decreased by 74% and 63%, respectively. Of the three configurations of bar code technology studied, the two configurations that required staff to scan all doses had a 93% to 96% relative reduction in the incidence of target dispensing errors and 86% to 97% relative reduction in the incidence of potential ADEs. However, the configuration that did not require scanning of every dose had only a 60% relative reduction in the incidence of target dispensing errors, and an increased (by 2.4-fold) incidence of target potential ADEs.

"We further tried to make the argument that in the two configurations that did well, bar code scanning happened in different ways," adds Poon. "In one, the identity of the meds was verified when they were stocked and when they were taken out for dispensing. In the other, scanning was not required when the meds were stocked, but when they were taken out every single dose had to be scanned."

In the third process, Poon explains, when the meds were taken out, if staff were trying to dispense say, 10 bags, the way the software worked it only mandated that the techs scan one of the 10 bags.

Verify every dose

The research revealed to Poon that medication dispensing is not a linear process. "What comes out of the pharmacy can come back," he explains. "For example, you may dispense an antibiotic that the patient does not need, so it is put back on the shelf. That's why if you do not scan meds when they are stocked, or if you don't scan every single dose, dispensing errors can happen."

Accordingly, the authors concluded that bar coding systems should be configured to mandate scanning of each dose at least once during the dispensing process. "You should definitely select one that does that, or at the very least, every single dose should be verified somehow by barcode scanning," says Poon, who says he is now conducting a cost-benefit analysis of the systems.

Another thing that surprised Poon during his research was just how many meds are dispensed — and accordingly, just how many errors can occur at a single hospital pharmacy.

"Pharmacies dispense a lot of meds; ours, for example, does about 6 million doses in a year. So, even if your error rate is very low, you still get a very substantial amount of errors. Using the bar code technology, even if you take all three systems into account, we would have been able to reduce ADEs by about 60%. That means we were preventing about 6,000 potential ADEs every year — which is a handsome number."


  1. Poon EG, Cina JL, Churchill W, et al. Medication dispensing errors and potential adverse drug events before and after implementing bar code technology in the pharmacy. Ann Intern Med. 2006;145:426-434.

[For further information, contact: Eric Poon, MD, MPH, Assistant Professor of Medicine, Harvard Medical School, and associate physician, Brigham & Women's Hospital, Boston, MA. Phone: (617) 732-6382.]