Which of the following additives used in blood sugar (glucose) vial in laboratory?

NORCET 3 - 2022 (Shift-2)

Biochemistry & Nutrition

Easy

Appeared in: NORCET 3 - 2022 (Shift-2)

Explanation

Sodium fluoride is the correct additive for blood glucose testing vials.
It acts as a glycolytic inhibitor, preventing the enzymes in blood cells from consuming glucose after the sample is collected.
This preservation ensures an accurate measurement of the patient's true glucose level.
Sodium fluoride is found in gray-topped collection tubes, often paired with an anticoagulant like potassium oxalate.

Option A: Sodium chloride (a major component of saline) is not used as a standard additive in blood collection tubes for preserving samples.
Option B: Sodium bicarbonate is a buffering agent used to treat metabolic acidosis or alkalinize urine; it is not used as an additive in blood glucose collection tubes.
Option D: Sodium citrate is an anticoagulant used for coagulation studies (e.g., PT, aPTT) and is found in light blue-top tubes. It does not inhibit glycolysis, so it is unsuitable for glucose testing.

Visual 1: Infographic: A chart showing the different types of vacutainer tubes with their cap colors, additives, mechanisms of action, and common laboratory uses. This helps visually link the gray top to sodium fluoride and glucose testing.
Visual 2: Flowchart: A simple diagram illustrating the process of glycolysis and highlighting the step where the enzyme 'enolase' works, showing an 'X' over it labeled 'Sodium Fluoride action'.

Clinical Relevance

Nursing practice connection: Knowing Additives in blood collection tubes for laboratory analysis helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
A nurse's primary role in phlebotomy is to ensure sample integrity by selecting the correct tube for the ordered test. Using the wrong tube is a major pre-analytical error that can lead to incorrect diagnosis and treatment.
After drawing blood into a gray-top tube, it is crucial to gently invert it 8-10 times to ensure the sodium fluoride is mixed with the blood to effectively stop glycolysis.
What if? If a nurse accidentally draws a glucose sample into a green-top (heparin) tube and there is a delay in getting it to the lab, the glucose value reported will likely be falsely low because glycolysis will continue unchecked. This could lead to a missed diagnosis of hyperglycemia or an unnecessary intervention for perceived hypoglycemia.

How to Approach the Question

First, identify the core of the question: it's asking for the specific chemical additive used for preserving blood glucose samples.
Recall or look for information linking laboratory tests to specific blood collection tubes (vacutainers). The color of the tube cap is the key identifier.
Associate the 'glucose test' with the 'gray-top tube'.
Remember the additive contained in the gray-top tube. The primary preservative for glucose is sodium fluoride because it stops glycolysis.
Evaluate the other options. Sodium citrate (light blue top) is for coagulation, and the other salts are not standard additives for this purpose. This confirms sodium fluoride is the unique and correct answer.

Concept Tested & Keywords

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