Biological contamination of insulin pens in a hospital setting.

Purpose: Biological contamination of insulin pens in a hospital setting was studied.
Methods: This prospective study, conducted at two hospitals within a multihospital system, examined 125 insulin pens that had been returned to the inpatient pharmacies after patient discharge and were refrigerated for up to 48 hours before laboratory testing. Insulin was removed from the 125 pens and examined microscopically for the presence of nucleated cells and red blood cells (RBCs). Positive samples were examined by a pathologist to determine the cell types present. An immunochromatographic assay was used to determine the presence of free hemoglobin in the insulin. The 10 control samples were negative on microscopic examination.
Results: Out of 125 insulin pens, 7 (5.6%) tested positive for cells or hemoglobin. Microscopic examination revealed six positive samples containing a total of nine cells, including macrophages, squamous cells, and an RBC. The sample containing the RBC was not the same sample that tested positive for hemoglobin. Based on findings of intact cells and hemoglobin in insulin pens after administration, the potential exists for transmission of infectious agents from patient to patient if a single pen cartridge is used to administer insulin to multiple patients, even if a new needle is used for each individual.
Conclusion: Examination of 125 insulin pens used in hospitals revealed hemoglobin in 1 pen and at least one cell in another 6 pens. The nine detected cells consisted of four squamous epithelial cells, four macrophages, and one RBC.