HesapHanem

Delta Ratio Calculator

Enter the anion gap and bicarbonate, adjusting the normal values if needed.

How it is calculated

Anion gap (AG) and bicarbonate (HCO3) are entered in mmol/L. The tool computes delta ratio = (AG − normal AG) ÷ (normal HCO3 − HCO3). The normal values default to 12 for AG and 24 for HCO3 and can be changed to match your lab. The ratio is only defined while bicarbonate is below the normal value; if HCO3 is equal to or above it, or a required field is empty, no result is shown. The ratio is placed in a band: below 0.4, 0.4 to 1, above 1 up to 2, and above 2, each with a one-line interpretation. A value of exactly 1 falls in the 0.4 to 1 band. An anion gap at or below the normal value gives no result either, because a negative ratio is not shown. The result is an educational aid, not a diagnosis.

Worked example

Suppose AG = 20 mmol/L and HCO3 = 14 mmol/L, with the default normals of 12 and 24. The rise in the anion gap is 20 − 12 = 8. The fall in bicarbonate is 24 − 14 = 10. The delta ratio is 8 ÷ 10 = 0.80. That lies in the 0.4 to 1 band, which the tool describes as suggesting a mixed high anion gap and normal anion gap metabolic acidosis.

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Common mistakes

  • Typing sodium or chloride into the anion gap box. The tool takes the finished anion gap, which you work out beforehand, and it must be measured the same way as the normal AG you compare it with.
  • Putting a bicarbonate at or above the normal (for example 24 or 28) and expecting a ratio. The formula needs bicarbonate below normal, so the tool returns nothing.
  • Entering an anion gap at or below the normal value and expecting a ratio. The ratio describes a raised gap, so with the default normal of 12 a gap of 12 or less gives no result.
  • Leaving the normal values at 12 and 24 when your laboratory uses different reference values; change them so both sides of the ratio use the same baseline.
  • Reading a ratio of exactly 1.00 as the start of the 1 to 2 band. The tool puts 1.00 in the 0.4 to 1 band, and a rounded 1.00 may really be 0.996 or 1.004.
  • Using the ratio alone. It compares two changes and says nothing about the cause, so it is read together with the full blood gas and clinical picture.

Sources

About this calculator

The delta ratio (sometimes called delta-delta or ΔAG/ΔHCO3) helps clinicians tell whether a patient’s metabolic acidosis is a pure high-anion-gap process or a mixed disorder: it compares how far the anion gap has risen above normal to how far the bicarbonate has fallen below normal, using Delta ratio = (AG − 12) / (24 − HCO3) with 12 and 24 as the typical normal reference values (adjustable when local lab norms differ).

A ratio above 1 and up to 2 suggests a straightforward high-anion-gap metabolic acidosis (such as diabetic ketoacidosis), a ratio between 0.4 and 1 points toward a mixed high-anion-gap and normal-anion-gap acidosis, a ratio below 0.4 suggests a concurrent normal-anion-gap (hyperchloremic) acidosis, and a ratio above 2 suggests a concurrent metabolic alkalosis or pre-existing compensated respiratory acidosis, since the bicarbonate has not fallen as much as the rising anion gap would predict. Physicians and intensive-care clinicians use it alongside arterial blood gas and electrolyte panels to unravel mixed acid-base disorders; enter the anion gap and bicarbonate, adjusting the normal values if your lab uses different reference ranges. Not medical advice.

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  • Editorial team

    The ratio only makes sense when the anion gap is raised and the bicarbonate is below normal. If the gap is at or below the normal value you entered, or the bicarbonate is at or above its normal, the page shows no result rather than a number. Both normal values are editable, so match them to your lab's reference ranges. This is an educational aid; interpretation belongs to the treating clinician. What normal anion gap does your lab use?

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