A light blue color-coded collection tube is used for:

Appeared in: AIIMS CRE, SNO-2024

Explanation

Light blue top tubes contain the anticoagulant sodium citrate.
Sodium citrate works by binding to calcium, which is essential for the clotting cascade, thereby preventing the blood from clotting.
This process preserves the coagulation factors in the plasma, making it the required sample for tests that measure clotting function.
Therefore, these tubes are used for coagulation studies such as Prothrombin Time (PT), activated Partial Thromboplastin Time (aPTT), and fibrinogen levels.

Option A: Glucose testing requires a tube that prevents the breakdown of glucose by blood cells after collection.
Option C: Electrolyte panels are chemistry tests that can be run on either plasma or serum.
Option D: Blood cultures require a sterile medium to grow microorganisms and identify infections.

Visual 1: Infographic - A chart showing the different color-coded blood collection tubes, their additives, and their primary laboratory uses. This helps in quick visual recall of the 'order of draw' and tube functions.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Phlebotomy: Blood Collection Tube Color Codes as background academic context rather than a clinical decision trigger.
Using the correct tube for the correct test is a critical patient safety measure. An incorrect tube can lead to erroneous results, requiring a painful and time-consuming redraw, and delaying diagnosis and treatment.
Nurses must be proficient in the 'order of draw' to prevent cross-contamination of additives. The light blue tube is drawn after blood cultures (if any) but before tubes with other anticoagulants or clot activators.
What if the light blue tube is not filled to the indicated line? The 9:1 blood-to-additive ratio will be incorrect. An underfilled tube will have excess citrate, leading to falsely prolonged PT/INR results, which could cause a clinician to inappropriately decrease a patient's anticoagulant medication, increasing their risk of clotting.

How to Approach the Question

Identify the key terms in the question: 'light blue' and 'collection tube'.
This is a factual recall question testing your knowledge of phlebotomy equipment.
Mentally access your knowledge of the color-coding system for blood collection tubes.
Associate the color 'light blue' with its specific additive, which is sodium citrate.
Recall the function of sodium citrate as an anticoagulant that preserves clotting factors.
Connect this function to its primary use, which is for 'coagulation studies'.

Concept Tested & Keywords

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Practise the full AIIMS CRE, SNO-2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.