When you or a family member are admitted to the hospital, you expect that the room will be cleaned and disinfected thoroughly. You do not expect to find half-used tissue paper boxes or leftover bandages from the previous patient. To the contrary, patients expect that hospitals will take all necessary precautions to avoid spreading disease, including disposing of patients’ medications when they are discharged from a facility.

Perhaps the only exception to the current practice of single-use, single-patient hospital supplies is blood glucose test strips. Hospitals and other institutions often procure blood glucose test strips in 25- or 50-count vials and bring them from patient to patient and room to room for testing purposes. Testing sites range from acute care hospitals, outpatient clinics, skilled nursing facilities and long term care facilities to prisons, shelters, surgery centers, schools, and camps.

Regardless of testing site, this practice of multi-strip vial use has come into focus as yet another potential source of contamination for patients undergoing blood glucose testing, along with the well-documented risks of sharing blood glucose meters and capillary puncture devices (1).

CDC and FDA Guidance on Shared Diabetic Supplies

The position of the Centers for Disease Control and Prevention on shared diabetic supplies is clear: Unused supplies such as blood glucose test strips taken to a patient’s bedside should not be used for another patient because of possible inadvertent contamination (2).

The Food and Drug Administration (FDA) regulates these test strips as medical devices. In the home testing market, FDA advises consumers to buy only unopened vials of glucose test strips designed for their meter and never to purchase “pre-owned” test strips (3), which often are sold at a discount. FDA advises against their use because consumers would not be able to determine several factors, such as whether the strips were stored properly, expired, or contaminated by the previous owner.

Of course, this guidance is directed at consumers. But given that assisted blood glucose testing has many of the same elements of risk as self-blood glucose testing—such as capillary blood testing spatter and potentially shared test strips in vials—these warnings also are noteworthy for healthcare professionals.

Bacterial Contamination of Blood Glucose Test Strips

In 2011, an independent U.K. study found serious contamination of test strips: 38 of 148 strips (25.7%) from 50-count vials in use at an acute care hospital tested positive for bacteria. Pathogens included enteric and skin flora but no multidrug-resistant pathogens. Importantly, there was not a statistically significant association between multi-patient vial use (non-intensive care units) and single-patient vial use (intensive care units) and contamination.

This lack of association suggested that the key contamination step occurs when caregivers repeatedly enter a vial to retrieve a strip—the same process in single-patient and in multi-patient vial use. Strips from only one manufacturer and a single institution were included in this study. Unopened vials were not found to harbor bacteria (4). Vials are currently manufactured under nonsterile conditions.

The following year, a study of strips from opened vials in use at five hospitals and from three manufacturers confirmed the previous findings. The majority of opened vials from two manufacturers of strips-in-vials (vendors not previously studied in the first paper) had bacterial contamination of strips. The percentage of strips contaminated within each vial varied. One colony-forming unit (CFU) per strip was considered a positive result. Strips were contaminated by fecal and skin flora, including Enterococcus faecium and Staphylococcus aureus. The authors tested unopened vials as a control, finding a 4% contamination rate.

The authors also retrieved individually wrapped strips from a third manufacturer in use at one hospital and found a 3% bacterial contamination rate. Of note, this was an industry-sponsored study from the singly packaged strip manufacturer (5).

In 2013, investigators in Spain compared bacterial contamination between individual, single-use packets at one hospital versus multi-use vials of 50- and 100-count in two hospitals. They used unopened vials from each hospital as controls. A number equal or higher than two CFU per strip was considered a positive result. Of 423 glucose test strips collected and cultured, the authors found that 7% of individually packed strips were contaminated versus 45% of strips packed in multi-use vials (p < .001). Pathogens included skin flora and a high percentage of methicillin-resistant species, including Staphylococcus epidermidis and Staphylococcus hemolyticus (6).

Despite the differences in technical methods in these studies, the researchers replicated the findings of widespread bacterial contamination in glucose test strips from multi-strip vials in use in hospitals. These diverse investigations also found enteric and skin flora—including resistant strains.

The Issue of Glucose Strip Wastage

If vials were designated for single-patient use, unused strips would represent wastage when discarded, akin to pharmaceutical wastage. The financial consequences of discarding unused test strips are unique to any given facility depending on the vial count, patient length of stay, patient volumes, percentage of patients being tested, and other variables.

One independently developed model of the costs of test strip vial wastage projected costs of strip wastage for one healthcare facility comparing 50- and 25-count vials and found that the former more than doubled wastage. The authors underscored that vial count and offering of individually wrapped strips could influence vendor selection if healthcare facilities adopted the practice of one vial: one patient (7).

Glucose Test Strip Handling Hazards

The practice of a designated glucose test strip vial for each patient may not deal with the root cause of the contamination issue, as suggested by the findings from the U.K. study. In that study, the investigators did not see any reduction in contamination with a single-patient vial designation (4).

The opening of a strip vial is small relative to the size of two fingers needed to grasp a single test strip. This leads to repeat touching of strips in the vial, attempts to shake out a strip, and accidental strip spillage onto nearby contaminated surfaces or floors. Equipment in intensive care units can harbor bacteria with the same antibiotic susceptibility profiles of patient isolates (9). Yet most hospitals do not have protocols for what to do with spilled strips, so spilled, contaminated strips may be returned to the vial. One manufacturer has developed a spill-proof vial in response to patient dissatisfaction with home testing options (8).

The impact of vial count has not been studied as an independent factor in strip contamination. The percentage of strips remaining in the vial does not appear to be a statistically significant predictor of contamination (4).

Perhaps most importantly, the practice of repeatedly entering a vial and touching the test strips under nonsterile conditions yields repeated opportunities for contamination in both directions. Caregivers contaminate their hands after direct patient contact and also after touching surfaces and equipment. Inadequate hand hygiene before and after entering a patient zone and performing blood glucose testing may result in cross-transmission of pathogens and patient colonization or infection (9). Until improved system design—such as glucose biosensors or touchless testing systems—eliminates current testing processes so fraught with contamination risk, the best prevention is meticulous hand hygiene.

Sharon Markham Geaghan, MD is an associate professor emerita of pathology at Stanford University in Stanford, California. +Email: sgeaghan@stanfordmed.org

References

1. Geaghan SM. Infection transmission associated with point of care testing and the laboratory’s role in risk reduction. EJIFCC 2014;25:188-94.
2. Centers for Disease Control and Prevention. Recommended infection-control and safe injection practices to prevent patient-to-patient transmission of bloodborne pathogens. www.cdc.gov/hepatitis/populations/pdfs/diabetes_handout.pdf. (Accessed November 16, 2017).
3. Food and Drug Administration. How to Safely Use Glucose Meters and Test Strips for Diabetes. https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm049051.htm. Accessed November 27, 2017.
4. Vanhaeren S, Duport C, Magneney M, et al. Bacterial contamination of glucose test strips: not to be neglected.
Am J Infect Control 2011; 39:611-3.
5. Ng R, Koo S, Johnston R. Multicenter evaluation of bacterial contamination of glucose test strips.
Clin Chim Acta 2012;413:1485-7.
6. Pérez-Ayala M, Oliver P, Rodríguez, Cantalejo F.
Prevalence of bacterial contamination of glucose test strips in individual single-use packets versus multiple-use vials.
J Diabetes Sci Technol 2013;7:854-62.
7. Nichols JH. Estimated strip wastage from glucose meter infection control recommendations. Clin Chem Acta 2012; 414:91-2.
8. Harvey C, Koubek R, Bégat V, et al. Usability Evaluation of a Blood Glucose Monitoring System with a Spill-Resistant Vial, Easier Strip Handling, and Connectivity to a Mobile App: Improvement of Patient Convenience and Satisfaction. J Diabetes Sci Technol 2016;10:1136-41.
9. Russotto V, Cortegiani A, Raineri SM, et al. Bacterial contamination of inanimate surfaces and equipment in the intensive care unit. J Intensive Care 2015; 3:54.


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