When Performing Capillary Draws: What Is the Correct Order of Draw?
Capillary blood draws are a common procedure performed in healthcare settings, especially for patients who require frequent blood tests or have difficult veins. While the process may seem straightforward, it is essential to follow the correct order of draw to ensure accurate results and minimize the risk of contamination. In this article, we will discuss the correct order of draw for capillary blood collection and address common questions related to this procedure.
The correct order of draw for capillary blood collection is as follows:
1. Blood Gas/Electrolytes – If blood gas analysis or electrolyte testing is required, it should be the first tube collected. This ensures that the results are not affected any contamination from subsequent tubes.
2. Coagulation Studies – If coagulation studies, such as prothrombin time (PT) or activated partial thromboplastin time (aPTT), are necessary, this tube should be collected next. Coagulation testing requires a blood sample that is free from anticoagulants present in other tubes.
3. Complete Blood Count (CBC) – The tube for a CBC, including hematology parameters like white blood cells, red blood cells, and platelet count, is collected after coagulation studies. This order prevents contamination from anticoagulants used in coagulation tubes.
4. Chemistry Tests – Tubes for chemistry tests, including liver function tests, kidney function tests, and blood glucose levels, should be collected next. These tests require a serum or plasma sample, and the order of draw prevents contamination from other tubes.
5. Serology – Tubes for serology tests, such as tests for infectious diseases or autoimmune disorders, should be collected after chemistry tests. This order reduces the risk of cross-contamination between tubes.
6. Microbiology – Tubes for microbiology testing, including blood cultures, should be collected next. Microbiology samples should be collected before any tubes containing anticoagulants to avoid contamination.
7. Immunology – Tubes for immunology tests, such as tests for allergies or immune disorders, should be collected after microbiology tubes. This order helps prevent contamination from other tubes.
8. Endocrinology – Tubes for endocrinology tests, including thyroid function tests or hormone levels, should be collected next. This order minimizes the risk of contamination from other tubes.
9. Blood Bank – If blood bank testing is required, the tube for this purpose should be collected after endocrinology tubes. This order ensures accurate blood typing and compatibility testing.
10. Molecular Diagnostics – Tubes for molecular diagnostic tests, such as DNA or RNA analysis, should be collected after blood bank tubes. This order prevents contamination from other tubes.
11. Toxicology – Tubes for toxicology testing, including drug screening, should be collected after molecular diagnostic tubes. This order helps avoid contamination from other tubes.
12. Flow Cytometry – Tubes for flow cytometry testing, such as immunophenotyping or cancer marker analysis, should be collected after toxicology tubes. This order minimizes the risk of contamination from other tubes.
13. Miscellaneous – Any additional tubes required for other specialized tests should be collected last. This order ensures that these samples are not contaminated other tubes.
Common Questions and Answers:
1. Can the order of draw vary depending on the laboratory or healthcare facility?
Yes, the order of draw may vary slightly depending on laboratory protocols or specific facility guidelines. It is important to follow the recommended order in your particular setting.
2. Why is the correct order of draw important?
The correct order of draw helps prevent contamination between tubes, ensuring accurate and reliable test results.
3. Can I use the same lancet for multiple capillary draws?
No, it is important to use a new, sterile lancet for each capillary blood draw to prevent cross-contamination.
4. How can I ensure proper disinfection of the puncture site?
Disinfect the puncture site with an alcohol swab and allow it to dry before performing the capillary draw.
5. Can I use an antiseptic instead of alcohol for disinfection?
It is recommended to use an alcohol-based disinfectant for capillary draws. Antiseptics may interfere with certain tests or cause hemolysis.
6. What if I accidentally collect too much blood in one tube?
If you collect more blood than required for a particular test, you may need to recollect the sample to ensure accurate results.
7. Is there a specific angle at which I should hold the lancet?
Hold the lancet perpendicular to the skin to minimize pain and ensure an adequate blood flow.
8. How long should I apply pressure to the puncture site after the draw?
Apply pressure to the puncture site for at least one minute to prevent bleeding and hematoma formation.
9. Can I mix the blood inside the capillary tube shaking it?
No, avoid shaking the capillary tube to prevent hemolysis or clot formation. Gently invert the tube to mix the blood with any additives.
10. Should I label the tubes before or after the capillary draw?
It is best to label the tubes before the capillary draw to ensure accurate identification of each sample.
11. Can I use a capillary tube for multiple tests?
No, each sample should be collected in a separate capillary tube to prevent cross-contamination.
12. Can I store capillary tubes at room temperature?
Capillary tubes should be stored according to the instructions provided the laboratory or manufacturer. Some tests may require refrigeration or freezing.
13. Can I use the same finger for multiple capillary draws?
Whenever possible, it is recommended to alternate fingers for capillary blood draws to prevent excessive trauma or pain to a single finger.
In conclusion, following the correct order of draw for capillary blood collection is crucial for accurate test results and reducing the risk of contamination. By adhering to the recommended sequence, healthcare professionals can ensure the integrity of each sample and provide reliable diagnostic information to patients and healthcare providers.