Collecting blood samples may seem straightforward, but adhering to the correct order of draw is crucial for accurate and reliable lab results. Improper order can lead to contamination, inaccurate test results, and even compromise patient safety. This cheat sheet provides a clear and concise guide to mastering the order of draw, ensuring you consistently produce high-quality samples.
Understanding the Importance of the Order of Draw
The order of draw is based on the additive present in each collection tube. Additives can leach from one tube into another, causing cross-contamination and compromising the integrity of the sample. Following the correct order minimizes this risk, ensuring the accuracy of various blood tests.
The Standard Order of Draw: A Comprehensive Guide
The standard order of draw, as recommended by CLSI (Clinical and Laboratory Standards Institute), is generally as follows:
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Blood Culture Bottles (Aerobic and Anaerobic): These are collected first to prevent contamination from other tubes. The alcohol swab should be allowed to dry completely before venipuncture to avoid falsely negative results.
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Sodium Citrate Tubes (Light Blue): These tubes contain an anticoagulant used for coagulation studies (PT, PTT, INR). It's crucial to fill these tubes completely to maintain the correct blood-to-anticoagulant ratio.
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Serum Tubes (Red): These tubes contain no additives and allow for serum separation after clotting. They're used for a wide range of tests, including chemistry and serology. Note that some red-top tubes may contain a clot activator to accelerate the clotting process.
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SST (Serum Separator Tubes) (Gold, Red/Gray): Similar to red-top tubes, but these contain a gel separator that helps separate serum from the clot during centrifugation. This simplifies the process for laboratory analysis.
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PST (Plasma Separator Tubes) (Light Green): These tubes contain lithium heparin as an anticoagulant and a gel separator, creating plasma samples. They are commonly used for plasma-based chemistry tests.
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Heparin Tubes (Green): These tubes contain heparin, another anticoagulant used for various chemistry tests requiring plasma. Sodium heparin and lithium heparin are common variations.
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EDTA Tubes (Lavender, Purple): EDTA (ethylenediaminetetraacetic acid) is an anticoagulant that preserves blood cells for hematology tests (CBC, ESR) and some molecular tests. It's essential to gently invert the tubes multiple times to adequately mix the additive.
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Oxalate/Fluoride Tubes (Gray): These tubes contain both sodium fluoride (an antiglycolytic agent) and potassium oxalate (an anticoagulant), primarily used for glucose testing and other metabolic studies. This combination prevents glycolysis (breakdown of glucose) and keeps glucose levels stable.
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Other Additives: Less common additive tubes exist for specific tests and should be drawn according to manufacturer instructions.
Visual Cheat Sheet: Quick Reference Guide
For a visual aid, consider creating a simple chart that displays the order of draw using color-coded tubes. This visual reminder will assist you in maintaining accuracy and consistency.
Advanced Considerations
- Pedriatric and Geriatric Patients: Modifications to the order of draw may be necessary depending on the patient's age and blood volume. Always prioritize minimizing the number of venipunctures.
- Specific Test Requirements: Some tests have specific collection requirements that override the standard order of draw. Always refer to the individual test instructions.
- Maintaining Aseptic Technique: Proper hand hygiene, disinfection, and needle safety are critical at every step of the blood collection process to minimize the risk of contamination.
Disclaimer: This cheat sheet provides general guidance. Consult your institution's policies, manufacturer's instructions, and relevant professional guidelines for specific protocols and procedures. Always prioritize patient safety and accurate test results.
