The human body is constantly struggling to find balance and stability. When H ions or extra acids are produced, the body suffers from a condition called metabolic acidosis. This leads to an increase in respiratory rate and a decrease in plasma levels. The anion gap is used to determine the exact cause of this pathology. Determines the unmeasured anions, i.e. phosphates, sulfates and proteins in the plasma. Calculating the anion gap is very simple knowing the standard formula that characterizes it. Keep reading.
Steps
Method 1 of 2: Calculate Your Anion Gap
Step 1. Determine your Sodium (Na⁺) level
A normal value is around 135-145 mEq / L. It is important to know your body's sodium level. You can find out your sodium level with a blood test that your doctor can prescribe for you.
Step 2. If necessary, determine your Potassium (K⁺) value
A normal value is 3.5–5.0 mEq / L. However, there is a different formula in which it is not necessary to know it. This is because the potassium value in the plasma is sometimes too low to matter.
Since there is a formula where potassium is not needed, you can also skip this step
Step 3. Determine your Chloride (Cl⁻) level
The normal chloride value is 97-107 mEq / L. Your doctor will order a test for this parameter as well.
Step 4. Determine the Bicarbonate (HCO₃⁻) level
The normal value is 22-26 mEq / L. This value can also be determined through the same series of tests.
Step 5. Find out about the normal reference value of the anion gap
This parameter is considered normal for values between 8 and 12 mEq / L if potassium is not considered. If potassium is used instead, the reference range changes to 12–16 mEq / L.
- Remember that all of these electrolyte levels can be determined with a blood test.
- Pregnant women may experience different levels. We will address this in the next section.
Step 6. Use the standard formula for the calculation
There are two formulas you can use to determine the anion gap:
- First formula: Anion Gap = Na⁺ + K⁺ - (Cl⁻ + HCO₃⁻). This formula is used if the potassium value is present. However, the latter is used more often than the former.
- Second formula: Anion Gap = Na⁺ - (Cl⁻ + HCO₃⁻). You can see that potassium is not present in this second equation. This is the formula that is used most frequently, but you can use one or the other according to your needs.
Step 7. Know when a result is within the norm
As already mentioned, a normal value is between 8 and 12 mEq / L without considering potassium, otherwise the range changes to 12-16 mEq / L. Here are two practical examples:
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Example 1: Na⁺ = 140, Cl⁻ = 100, HCO₃⁻ = 23
AG = 140 - (98 + 23)
AG = 24
The anion gap is 24. For this reason, the individual will test positive for metabolic acidosis
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Example 2: Na⁺ = 135, Cl⁻ = 100, HCO₃⁻ = 25
AG = 135 - (105 + 25)
AG = 10
The anion gap is 10. The value is normal and the person has no metabolic acidosis. It falls within the reference range between 8 and 12 mEq / L
Method 2 of 2: Understanding the Anion Gap
Step 1. What is the anion gap
The anion gap (GA) measures the difference between sodium and potassium cations and chloride and bicarbonate anions in patients who have liver problems and altered mental status - in other words, it measures the equilibrium level of pH. Represents the concentration of non-measurable anions in plasma, such as proteins, phosphates and sulfates. This sophisticated terminology pretty much indicates that your body produces the right things, but at the wrong levels.
Determining the value of the anion gap is essential in the case of blood tests aimed at determining the partial pressures of arterial gases or blood gas analysis. The basic concept is that the cation network and the anion charge must be identical for an organism to be balanced
Step 2. Understand the meaning of the anion gap
Its determination is especially important in patients suffering from kidney or gastrointestinal problems. The test does not ascertain the presence of any type of pathology. However, it serves to exclude some possibilities and allows you to narrow down the search field of the problem.
- The anion gap reveals the presence of metabolic acidosis if the body's pH levels are out of phase. Based on the result, it differentiates the causes of metabolic acidosis and helps confirm other test results. Consult your doctor for further information so that you understand the process.
- Let's take the case of a patient with lactic acidosis (a situation in which there is also an accumulation of lactate). In this circumstance, the serum bicarbonate levels will automatically decrease (due to accumulation), so when you go to calculate the anion gap value, you will notice how the result tends to increase.
Step 3. Know what awaits you during the test
An anion gap serum sample is taken from the vein using a separate separation tube. Here's what's going to happen:
- A nurse will draw your blood, most likely from your arm.
- He will ask you if you have latex allergies. If so, he'll use a different material to make sure you don't have an allergic reaction.
- Tell him if you have any medical conditions or are sensitive to certain medications that could cause excessive bleeding or if you have psychological problems related to the use of sharp objects, such as a needle.
- Your sample will be stored in a bio refrigerator and quarantined for analysis. Once the exam is complete, your doctor will contact you to discuss the outcome.
Step 4. How to interpret the results
The doctor will associate the results with your appearance, how you feel, and other related symptoms. When the final results arrive, it will let you know what the next steps will be. If he thinks the results may be wrong, he may require another test to confirm them.
- A low anion gap can be associated with various diseases, such as hypoalbuminemia or bromide poisoning. A normal result is expected in patients recovering from diabetic ketoacidosis or bicarbonate loss due to prolonged diarrhea.
- A high anion gap could indicate lactic acidosis or renal failure. Interpretation of results can be influenced by various factors and patient conditions.
- The normal anion gap level for pregnant women is slightly different. During the first trimester, the normal anion gap ranges from 0 to 20 mmol / L. During the second and third semester, the normal value drops to 10-11 and 18 mmol / L respectively.
Step 5. Understand what can interfere
Sample collection errors can occur and interfere with laboratory results. Time, dilution and sample size are important to get an accurate result. A delay in analyzing the sample and prolonged exposure to air could cause an increase in bicarbonate levels. In this way, the anion gap would be lowered by 2.5 mEq / L for each gram / dL of albumin concentration extracted from the blood. Your doctor should still be able to spot a similar situation (if not avoid the problem altogether).
An increasing anion gap needs further clinical investigation - for example, tests to detect serum lactic acid levels, serum creatine and serum ketones, medical tests - to rule out possible causes of anion gap acidosis
Advice
The value of the anion gap is not indicative of a specific pathology. An increase or decrease in value could be caused by several medical factors. The diagnostic results will be correlated with any clinical manifestations and verified through a series of other analyzes able to accurately diagnose the patient's medical condition.
