Blood Specimen Collection: Glucose Point-of-Care Screen (Ambulatory) - CE/NCPD

ALERT

Failure to follow manufacturer guidelines pertaining to glucose meter use may cause inaccurate results.

Do not milk the patient’s finger or wick blood onto the reagent strips; this may cause inaccurate results.

Failure to recognize inaccurate results can lead to errors in management and death.

Take extra care with a patient who takes medications that increase the risk for bleeding.^{undefined#ref5">5}

OVERVIEW

Blood glucose monitoring reveals individual patterns of blood glucose changes to aid with meal and activity planning and medication timing. Point-of-care capillary blood glucose testing also allows for a quick response to episodes of high blood glucose (hyperglycemia) or low blood glucose (hypoglycemia).

Obtaining capillary blood by skin puncture is an alternative when venipuncture cannot be performed to reduce the frequency of venous needlesticks and for self-management of diabetes mellitus. The procedure is less painful than venipuncture, and the ease of the skin puncture method makes it possible for patients and families to perform this procedure.

Point-of-care measurement of blood glucose requires obtaining a drop of capillary blood by skin puncture using a single-use, auto-disabling lancet and applying a drop of blood to a specially prepared chemical reagent strip. After the drop of blood is applied to the reagent strip, a reflectance meter provides a measurement of the blood glucose level.

Meters report a wide range of blood glucose values. If a value falls outside of a preset range, the meter reads "low" or "high." Because a low or high reading usually occurs only when blood glucose is in an extreme range, either of these readings must be treated as an emergency. Normal adult blood glucose levels (preprandial) typically fall in the 80 to 130 mg/dl range.² Less than 70 mg/dl is hypoglycemic, and more than 130 mg/dl is hyperglycemic.^1,2 Normal values may vary by age and may depend on the patient’s physical stressors and activity, mealtimes and foods consumed, insulin administration, and medications.

Meters may differ in several ways, including overall size, amount of blood needed for each test, testing speed, ability to store test results in memory, cost of the meter, and cost of reagent strips.⁶ Some meters recommend wiping away the first drop of blood with gauze and using the second drop for the test, whereas others recommend using the first drop of blood. For accurate results, the health care team member must follow the manufacturer’s instructions. Some meters are voice interactive, which is helpful for patients who have visual impairments. Some meters have memories that record multiple glucose readings for comparison over time.

Additionally, alternative blood glucose monitoring devices are available. Some meters allow for an alternative puncture site, including the forearm, palm, and thigh. Continuous interstitial glucose meters use a very small, fine biosensor inserted through the abdomen or the back of the arm that transmits continuous readings of interstitial glucose levels to a monitor or a computer (Figure 1). These systems support the patient with diabetes mellitus who requires assessment of glucose trends and patterns.⁶

SUPPLIES

See Supplies tab at the top of the page.

EDUCATION

• Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
• Provide information about blood glucose monitoring, including the reason for the test, an explanation of each step involved in obtaining the blood glucose measurement, and a description of the sensations the patient may feel during the test.
• Provide information on where the patient with diabetes mellitus can obtain testing supplies, if applicable. When possible, teach with the same meter that the patient will use at home.
• Provide the patient with information on where to obtain assistance if the glucose meter malfunctions.
• Instruct the patient on what to do and whom to contact if the glucose reading is out of range or if the meter malfunctions.
• Stress the importance of the timing of checking blood glucose levels, particularly in patients with diabetes mellitus.
• To advance education, ask the patient to explain the test and the results and to perform a return demonstration of the procedure.
• Encourage questions and answer them as they arise.

PROCEDURE

1. Perform hand hygiene and don gloves. Don additional PPE based on the patient’s need for isolation precautions or the risk of exposure to bodily fluids.
2. Introduce yourself to the patient.
3. Verify the correct patient using two identifiers.
4. Explain the procedure and ensure that the patient agrees to treatment.
5. Ensure that evaluation findings and blood glucose test results are communicated to the clinical team leader per the organization’s practice.
6. Determine whether a patient with diabetes mellitus understands how to perform the test and realizes the importance of glucose monitoring.
7. If the patient has not been diagnosed with diabetes, consider any history of hypoglycemia or hyperglycemia and related symptoms.
8. Determine whether conditions (e.g., fasting after meals, after certain medications, or before insulin doses) must be met before or after sample collection.
9. Determine if any risks exist for performing capillary puncture (e.g., low platelet count, anticoagulant therapy, bleeding disorders).
10. Evaluate the integrity of the skin being used as the puncture site. Inspect fingers, toes, or heels and avoid areas of bruising and open lesions. Consider alternative sites (e.g., palm, forearm, thigh) if the meter will provide accurate readings from these sites.
11. Clean and disinfect the meter per the manufacturer’s instructions.
12. Remove gloves, perform hand hygiene, and don clean gloves.
13. Instruct the patient to perform hand hygiene with soap and warm water. Assist the patient as needed.

    Rationale: Hand hygiene promotes skin cleansing and vasodilation at the selected puncture site. Handwashing establishes practice for the patient when the test is performed at home. A patient who has just eaten may have sugar on the hands, which would produce a false high reading.

14. Check the code and expiration date on the reagent strip container. Remove a reagent strip from the container and then tightly seal the cap.

    Rationale: The code on the test strip vial must match the code entered into the glucose meter. Expired strips are not guaranteed to give an accurate reading. Tightly sealing the cap protects the strips from accidental discoloration from exposure to air or light.

15. Turn the glucose meter on, if necessary.

    Rationale: Some meters are activated when the reagent strip is inserted and therefore do not have an on-off switch.

16. Ensure that the blood glucose meter is calibrated correctly per the manufacturer’s instructions.

    Rationale: Some devices must be calibrated; others require the timer to be zeroed. Each meter is adjusted differently. Calibration ensures an accurate reading.

17. Enter or scan the patient’s identifying information into the meter per the manufacturer’s instructions.

    Rationale: Some devices communicate patient information into laboratory records or the electronic health record using a unique identifier.

18. Choose the puncture site.
    1. Ensure that the puncture site is vascular.
    2. Select the lateral side of the finger; avoid the central tip of the finger, which has a denser nerve supply. If the meter allows, also consider using the forearm, thigh, or fleshy part of the hand.
19. Hold the finger being punctured in a dependent position (Figure 2).
20. Cleanse the site with an antiseptic swab and allow it to dry completely.

    Rationale: Alcohol from the swab may cause blood to hemolyze.

21. Obtain a blood sample.
    1. Remove the cover of the lancet or bloodletting device. Hold the lancet perpendicular to the puncture site and pierce the finger quickly in one continuous motion. Do not force the lancet.
    2. If using a single-use, auto-disabling lancet device with an automatic blade-retraction system, place the bloodletting device firmly against the side of fingertip or other selected site and push the release button, causing the needle to pierce the skin.

       Rationale: Using a single-use, auto-disabling device reduces the possibility of accidental needlesticks, preventing exposure to blood-borne pathogens.

22. Wipe away the first droplet of blood with a cotton ball or gauze as indicated.

    Rationale: The first drop of blood may be contaminated with the alcohol used for disinfection, which may provide an inaccurate result. Newer meters no longer require the first drop to be wiped away.

    Always follow the manufacturer’s instructions for specific directions because all meters are slightly different.

23. Gently squeeze the finger without touching the site until a sufficient droplet of blood has formed (Figure 3). Repuncture at a new site if the drop is not large enough to ensure accurate test results.

    Rationale: An adequate-size droplet is needed to activate the meter and obtain accurate results. Excessive squeezing of tissues during blood sample collection may contribute to pain, bruising, scarring, hematoma formation, or dilution of the sample with serous fluid.⁶ Reusing the same puncture site allows blood that is already clotting to interfere with results. Different meters require different amounts of blood. As blood enters the strip, the glucose device may signal if more blood is required or enough blood is obtained.

24. Apply the blood sample to the reagent strip per the manufacturer’s instructions (Figure 4). Some devices require the blood sample to be applied to the reagent strip before inserting the strip into the meter, whereas others require inserting the reagent strip into the meter before applying the blood sample.
25. Obtain the test results (Figure 5) (Figure 6).

    Rationale: The blood glucose test result appears on the screen in mg/dl. Some devices signal when the test is completed.

26. If the glucose meter displays “low” or “high” instead of a numeric result, repeat testing.

    Abnormal values must be evaluated immediately and appropriate treatment initiated per the organization’s practice.

    Rationale: The blood glucose test result assists with identifying trends and patterns in glucose levels and is useful for the management of insulin therapy and corrective management.⁴

27. Provide absorbent gauze or apply an adhesive bandage if needed to control bleeding at the puncture site or if the patient desires.
28. Turn the meter off.
29. Clean and disinfect the meter per the manufacturer’s instructions.
30. Reinspect the puncture site for bleeding or tissue injury.
31. Discard supplies, remove PPE, and perform hand hygiene.
32. Document the procedure in the patient’s record.

EXPECTED OUTCOMES

• Puncture site shows no evidence of bleeding or tissue damage.
• Blood glucose level is normal or within expected range for the patient.
• Sample is collected from, and results are documented for, the correct patient.
• Patient meets education goals for demonstrating procedure when applicable.
• Patient can explain the meaning of test results.

UNEXPECTED OUTCOMES

• Puncture site is bruised or continues to bleed.
• Inability to obtain adequate blood sample for testing.
• Blood glucose level is above or below target range.
• Glucose meter malfunctions.
• Patient expresses misunderstanding of procedure and results.

DOCUMENTATION

• Evaluation findings and blood glucose test results communicated to the clinical team leader per the organization’s practice
• Time that sample was obtained
• Appearance of puncture site
• Action taken if result was abnormal, including recording and reporting of abnormal blood glucose levels
• Unexpected outcomes and related interventions
• Education

PEDIATRIC CONSIDERATIONS

• Young children should be allowed to choose among approved puncture sites.
• The heel and great toe may be used as puncture sites in infants.
• An approved, single-use, auto-disabling lancet that does not puncture deeper than 2.4 mm and that punctures the outer aspect of the heel should be used with infants to avoid osteochondritis dissecans.³ Infection or abscess of the heel and necrotizing osteochondritis dissecans are serious complications of a heel-stick puncture in infants.
• Young children should be allowed to demonstrate the technique with a family member, as appropriate per their developmental level and skill. Incorporating a play activity should be considered for further understanding.
• Colorful adhesive bandages should be used for comfort and distraction if not contraindicated because of skin condition, allergy, or other reason.

OLDER ADULT CONSIDERATIONS

• Fingertips should be warmed to help facilitate obtaining the specimen.
• Some older adults have vision or dexterity problems that interfere with performing self-finger sticks.

REFERENCES

1. American Diabetes Association (ADA). (n.d.). The big picture: Checking your blood glucose. Retrieved March 19, 2024, from https://www.diabetes.org/healthy-living/medication-treatments/blood-glucose-testing-and-control/checking-your-blood-sugar
2. American Diabetes Association (ADA). (2021). Standards of medical care in diabetes—2021. Diabetes Care, 44(Suppl. 1), S1-S2. Retrieved March 19, 2024, from https://care.diabetesjournals.org/content/44/Supplement_1/S1
3. Anderson, C.E., Herring, R.A. (2022). Chapter 20: Pediatric nursing interventions and skills. In M.J. Hockenberry, C.C. Rodgers, D. Wilson, (Eds.), Wong’s essentials of pediatric nursing (11th ed., pp. 551-618). St. Louis: Elsevier.
4. Dickinson, J.K. (2023). Chapter 53: Diabetes. In M.M. Harding and others (Eds.), Lewis’ Medical-surgical nursing: Assessment and management of clinical problems (12th ed., pp. 1285-1321). St. Louis: Elsevier.
5. Joint Commission, The. (2024). Ambulatory Health Care: 2024 National Patient Safety Goals. Retrieved March 19, 2024, from https://www.jointcommission.org/standards/national-patient-safety-goals/ambulatory-health-care-national-patient-safety-goals/
6. U.S. Food and Drug Administration (FDA). (2019). Blood glucose monitoring devices. Retrieved March 19, 2024, from https://www.fda.gov/medical-devices/in-vitro-diagnostics/blood-glucose-monitoring-devices

ADDITIONAL READINGS

Centers for Disease Control and Prevention (CDC). (2011). Infection prevention during blood glucose monitoring and insulin administration. Retrieved March 19, 2024, from https://www.cdc.gov/injectionsafety/blood-glucose-monitoring.html

Clinical Review: Suzanne M. Casey, MSN-Ed, RN

Published: April 2024