What is the correct 'Order of Draw' for blood collection tubes?

AIIMS CRE, SNO-2024

Nursing Foundation

Easy

Appeared in: AIIMS CRE, SNO-2024

Explanation

The correct sequence for the given tubes is Culture, Citrate, Heparin, Oxalate.
This order is critical to prevent cross-contamination of additives between tubes, which can invalidate test results.
Blood culture tubes are always drawn first to maintain sterility and prevent bacterial contamination from non-sterile tube tops.
Citrate tubes (for coagulation) are drawn next, as other additives like heparin or oxalate would alter clotting times.
Heparin tubes follow citrate tubes.
Oxalate tubes are drawn last because their additives (potassium oxalate, sodium fluoride) can severely interfere with electrolyte and coagulation tests if they contaminate other tubes.

Option A: This order is incorrect because blood culture tubes must always be drawn first to ensure the sample remains sterile and is not contaminated by additives from other tubes.
Option C: This order is incorrect. Oxalate tubes are drawn last because their additives (potassium oxalate and sodium fluoride) can cause significant interference with other tests, such as elevating potassium levels and binding calcium needed for coagulation tests.
Option D: This order is incorrect because blood culture tubes must be drawn first to maintain sterility. Drawing a heparin tube before a culture tube introduces a high risk of contamination.

Visual 1: Infographic: A chart showing the correct order of draw with images of the corresponding colored-top tubes, their additives, and common laboratory tests. This provides a quick visual reference for memorization.

Clinical Relevance

Nursing practice connection: Knowing Order of Draw in Phlebotomy helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Following the correct order of draw is a fundamental patient safety and quality assurance measure in nursing. Failure to do so can lead to incorrect diagnoses, inappropriate treatment, and the need for painful and costly re-draws.
A common nursing intervention is to gently invert tubes with additives 8-10 times immediately after collection to ensure proper mixing. Vigorous shaking can cause hemolysis, which also invalidates results.
What if you are using a butterfly (winged infusion) set to draw a light blue (citrate) tube? You must first draw a discard tube (a plain red or another light blue tube) to prime the tubing. This removes the air from the tubing, ensuring the correct blood-to-additive ratio is achieved in the actual citrate tube, which is critical for accurate coagulation results.

How to Approach the Question

Identify the core concept being tested, which is the 'Order of Draw' for phlebotomy.
Recall the fundamental principle: the sequence is designed to prevent additive cross-contamination.
Remember the key rules: Sterile tubes (blood cultures) are always first, and tubes with additives that cause the most interference (like gray-top oxalate tubes) are last.
Evaluate each option against this principle. Start by looking for the option that places 'Culture' first.
Eliminate options that violate this primary rule. In this case, options A, C, and D are immediately incorrect because they do not start with 'Culture'.
Confirm the rest of the sequence in the remaining option (B): Citrate (coagulation), Heparin, then Oxalate (glycolytic inhibitor), which follows the standard protocol.

Concept Tested & Keywords

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