The study covered in this summary was published in The Lancet as a preprint and has not yet been peer reviewed.
Key Takeaways
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Allergic sensitization at insulin pump sites is common.
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Pump vs control sites had greater vessel density, fibrosis, fibrinogen, and inflammation including eosinophils, insulin-like-growth factor-1 (IGF-1), and transforming growth factor (TGF) β-3, as well as fat necrosis.
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The tissue changes resulting from these skin responses could potentially lead to the infusion site failures commonly seen in clinical practice.
Why This Matters
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Approximately 55% of diabetic ketoacidosis episodes in patients using insulin pumps are reportedly due to “pump/tubing” malfunctions.
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Anecdotally, pump discontinuation is common after 20 years, owing to site failures, but just how frequently this occurs is unknown.
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Little is understood about the cutaneous changes from chronic insulin infusion and how this may impact infusion site failure.
Study Design
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Optical coherence tomography (OCT) was performed immediately before skin punch biopsy samples were collected at three sites: a “current site,” a “recovery site” ― used 3 days prior to biopsy ― and a “control” site never used for any insulin infusion or injection.
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Analysis included 25 participants with a total of 75 skin sites.
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Pump brands used were Medtronic, Tandem, and Omnipod, with steel, teflon, and Omnipod infusion sets used.
Key Results
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Cutaneous symptoms at pump sites were common, with 93.3% of participants reporting itching and 76.7% reporting skin redness.
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The OCT angiography microvascular maps showed increased blood vessels in both current and recovery pump sites vs control sites.
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Statistical analysis showed a significant difference in vessel area density between pump and control sites (P < .0001) and between recovery and current pump sites (P < .001).
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In histologic analysis, both current and recovery sites showed increased fibrosis, fibrinogen, inflammation, vascularity, and fat necrosis compared to control sites (all P < .001), with no significant differences seen between the current and recovery sites.
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No eosinophils were observed in skin biopsy samples at the control sites, whereas eosinophils were identified in 73% of skin biopsy samples from the current sites (P < .01) and 75% of skin samples from the recovery sites (P < .01).
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All study participants had eosinophils (range, 0–31/high power field; median, 4) identified in at least one current and/or recovery insulin infusion sites, located deep in the dermis near the interface with the fat.
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There was no significant association between the type of insulin or pump brand and number of eosinophils.
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Higher eosinophil counts were seen in patients using pumps for <10 years compared to those using pumps >20 years (P = .02).
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Immunohistochemical staining also showed differences between current/recovery sites and the control site for insulin-like-growth factor-1 (IGF-1) and transforming growth factor β-3, but no difference with IGF1 receptor.
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There were no differences in either OCT or histologic findings based on duration of pump use or with prior use of animal insulin.
Limitations
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The sample size was relatively small.
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The cohort consisted of adults who were mostly White, with normal weight and with excellent glycemic control.
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The findings may not be generalizable to other populations, particularly younger patients.
Disclosures
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The study was funded by the Leona M. and Harry B. Helmsley Charitable Trust.
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Lead author Kalus has no disclosures, but one author reports grants and/or consulting fees from various sources, including Insulet, Medtronic, Dexcom, Abbott Diabetes, Roche, Bigfoot, and Lifescan.
This is a summary of a preprint research study, “Evaluation of Insulin Pump Infusion Sites in Type 1 Diabetes,” by Andrea Kalus, MD, of the University of Washington School of Medicine, Seattle, and colleagues. This study has not yet been peer reviewed.
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