Determination of the serum anion gap (AG) is an important step in the differential diagnosis of acid-base disorders, especially metabolic acidosis (Emmett, 2023). The delta ratio in metabolic acidosis is a calculated value used to help determine the presence of concurrent acid-base disorder in patients with metabolic acidosis.
   
The ratio gives one of four results, presented in the table below.

Delta Ratio	Assessment
Less than 0.4	A normal anion gap metabolic acidosis (i.e., hyperchloremia)
0.4-1	A mixed high anion gap metabolic acidosis and normal AG acidosis Note the ratio if ogten less than 1 in acidosis associated with renal failure.
1-2	An uncomplicated high anion gap metabolic acidosis, also called a “pure high anion gap metabolic acidosis” Latic acidosis: average value 1.6 DKA: more likely to have ratio closer to 1 due to loss of urine ketones
Greater than 2	Suggests a pre-existing elevated HCO3- Concurrent metabolic acidosis OR Pre-existing compensated respiratory acidosis

References:

Emmett, M. (2022, May 4) The delta anion gap/delta HCO3 ratio in patients with a high anion gap metabolic acidosis. UpToDate. https://www.uptodate.com/contents/the-delta-anion-gap-delta-hco3-ratio-in-patients-with-a-high-anion-gap-metabolic-acidosis

Rastegar A. (2007). Use of the DeltaAG/DeltaHCO3- ratio in the diagnosis of mixed acid-base disorders. Journal of the American Society of Nephrology: JASN, 18(9), 2429–2431. https://doi.org/10.1681/ASN.2006121408