Why Do You Wipe The First Drop Of Blood

[Amie Mandy]

Bloodglucose 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.

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

The information given here supplements that given in Chapter 2. Users of these guidelines should read Chapter 2 before reading the information given below. This chapter covers background information (Section 7.1), practical guidance (Section 7.2) and illustrations (Section 7.3) relevant to capillary sampling.

Capillary sampling from a finger, heel or (rarely) an ear lobe may be performed on patients of any age, for specific tests that require small quantities of blood. However, because the procedure is commonly used in paediatric patients, Sections 7.1.1 and 7.1.2 focus particularly on paediatric capillary sampling.

The finger is usually the preferred site for capillary testing in an adult patient. The sides of the heel are only used in paediatric and neonatal patients. Ear lobes are sometimes used in mass screening or research studies.

Selection of a site for capillary sampling in a paediatric patient is usually based on the age and weight of the patient. If the child is walking, the child's feet may have calluses that hinder adequate blood flow. Table 7.1 shows the conditions influencing the choice of heel or finger-prick.

A lancet slightly shorter than the estimated depth needed should be used because the pressure compresses the skin; thus, the puncture depth will be slightly deeper than the lancet length. In one study of 52 subjects, pain increased with penetration depth, and thicker lancets were slightly more painful than thin ones (67). However, blood volumes increased with the lancet penetration and depth.

With skin punctures, the haematology specimen is collected first, followed by the chemistry and blood bank specimens. This order of drawing is essential to minimize the effects of platelet clumping. The order used for skin punctures is the reverse of that used for venepuncture collection. If more than two specimens are needed, venepuncture may provide more accurate laboratory results.

Show the child that you care either verbally or physically. A simple gesture is all it takes to leave the child on a positive note; for example, give verbal praise, a handshake, a fun sticker or a simple pat on the back.

Adhere strictly to a limit on the number of times a paediatric patient may be stuck. If no satisfactory sample has been collected after two attempts, seek a second opinion to decide whether to make a further attempt, or cancel the tests.

If there are traces of sugar on your fingers when you test, your results can be wonky. Always wash your hands with soap and warm water first. The gentle heat will help your blood flow so you can get a full drop. Be sure to dry off completely too; dampness can dilute your sample or hinder the chemical reaction that performs your test.

Accurate collection and recording of time is especially important with blood draws done right at 24 hours in order to avoid collecting blood before 24 hours of age. If you are collecting before 24 hours of age, please reference our Newborn Screening

The primary goal of these standards is to ensure the quality of blood spots collected from newborns. Poor quality specimens interfere with the screening process, potentially delaying the detection and treatment of an affected infant. If our staff receive a specimen of poor quality, we will request a repeat specimen from the birth provider.

Do not apply multiple layers of blood drops to the same circle. The circles are measured and should contain a set volume of blood. Layering can interfere with the accuracy of the test by providing a non-standard amount of blood or non-uniform analyte concentration. Excessive milking or squeezing of the puncture site can result in an unsatisfactory specimen because of hemolysis breaking down the blood cells to be analyzed or mixing tissue fluids in the specimen, which can dilute the blood.

For clinics, out-of-hospital birth providers, and parents who submit specimens infrequently, specimens can be brought to the delivery address above or mailed to the address below. Since high heat and humidity can affect some of the tests, leaving specimens in hot mailboxes or other warm locations should be avoided.

Within Minnesota, birth hospitals are legally responsible for arranging to have newborn screening administered to every infant in its care. This can be accomplished by screening the newborn in the birth facility or by having a protocol in place with a receiving hospital to screen the infant.

The following video was produced by PerkinElmer Genetics with input from the Minnesota Newborn Screening Program. This less than 5 minute video covers how to properly collect blood spot specimens for newborn screening.

The following video answers many frequently asked questions about blood spot collection, including the optimal timing of collection, drying of blood spots, and methods of collection. The video was produced in partnership by the Iowa State Hygienic Laboratory and Baby's First Test

Test using a control solution. Follow your typical blood-testing procedure, but use a liquid control solution instead of blood. These solutions usually come with your monitor and are available at most drugstores and pharmacies. Follow package directions.

Use liquid control solutions every time you open a new container of test strips, and then use the solutions occasionally as you use the strips. You generally should also use liquid control solutions if you drop your blood glucose meter, or whenever you get unusual results.

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Research design and methods: Capillary glucose concentrations were measured in two consecutive drops of blood in the following circumstances in 123 patients with diabetes: without washing hands, after exposing the hands to fruit, after washing the fruit-exposed hands, and during application of different amounts of external pressure around the finger. The results were compared with control measurements.

Conclusions: We recommend washing the hands with soap and water, drying them, and using the first drop of blood for self-monitoring of blood glucose. If washing hands is not possible, and they are not visibly soiled or exposed to a sugar-containing product, it is acceptable to use the second drop of blood after wiping away the first drop. External pressure may lead to unreliable readings.

For more information regarding collection of the newborn screening specimen when special circumstances exist such as premature infants, transfusions, facility transfers, TPN, etc. visit Specimen Collection - Special Circumstances.

Gloves should be worn for personal safety. Care should be taken to avoid contamination of blood collection circles with antiseptic solutions, powders, lotions or other materials which may contaminate and adversely affect the testing process.

The heel-stick is always the preferred method for collection of the newborn screening. If it is not possible to perform a heel-stick, please see the Alternative Methods for Collecting a Newborn Screen page for detailed information and instructions.

Quick delivery of specimens is imperative. Some disorders need to be identified, diagnosed and treated as soon as possible to prevent onset of clinical symptoms. For example, congenital adrenal hyperplasia and galactosemia may cause life-threatening symptoms by the first week of life.

It is important that submitting facilities are mindful of the time between collection and shipment. New national recommendations state that first screen specimens should arrive at the DSHS Laboratory within 24 HOURS AFTER COLLECTION. To facilitate timely identification and treatment of critical disorders, it is recommended that specimens be shipped via overnight courier and received in the laboratory for testing the day after collection.

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