Biologic material in needles and cartridges after insulin injection with a pen in diabetic patients

To evaluate the frequency of non-inert material, including cells, in needles and cartridges after insulin injection with pen-like devices in diabetic patients.

A prospective study was conducted in 120 insulin-treated diabetic patients who used pen-like devices. The patients, 46 women and 74 men, were 20-77 years old; 60% had type 1 diabetes, and 38% were overweight. Duration of diabetes ranged from 1 month to 40 years, and insulin therapy ranged from 1 month to 30 years. Insulin injection was performed by a trained nurse, using the patient's usual pen and cartridge. A cytopathological examination was performed on the material obtained from the needle and found in the cartridge after centrifugation. All slides were read by a single investigator.

In 62% of the patients, non-inert material was found, including squamous (32%) and epithelial (58%) cells. Biologic material was found in 30% of the needles and 58% of the cartridges, and in both needle and cartridge in 25% of the population. Biologic material was found more frequently in patients who had a longer duration of diabetes, who were treated with insulin for a longer time, and who performed injection in the thighs or upper arms (P < 0.05). In multivariate analysis, the presence of biologic material was associated with the duration of diabetes (R2 = 0.09; P < 0.01).

Our data suggest that biologic material can be trapped in the delivery system, including the cartridge, after an insulin injection with a pen-like device. Our results emphasize the strict need for individual use of insulin delivery systems, including cartridges and nonrefillable pens, especially in clinics and hospitals.