The anion gap is a mathematical calculation that reflects the difference between positively charged cations (potassium and sodium) and negatively charged anions (CO2 and chloride) in the blood. The ODX software uses potassium in the anion gap calculation while many labs do not. Using potassium in the equation will increase the accuracy of the evaluation.
Incorporating potassium (a cation) along with sodium (cation), chloride (anion) & bicarbonate (anion), will, in our opinion, give you a more accurate picture of the actual "anion gap". Technically the anion gap reflects unmeasured compounds, mostly anions, in the blood. Things that can increase the anion gap include ketones, lactate, creatinine, alcohols, salicylic acid, and acetaminophen (Brubaker 2021).
Serum protein levels can affect the anion gap as well. An increase in albumin, which is negatively charged, can increase the anion gap while a decrease in albumin can reduce it. Other factors affecting the anion gap include hyperlipidemia, aldosterone levels, gastrointestinal loss of electrolytes, and certain medications (Pagana 2019). A decrease in phosphorus (anion) or an increase in magnesium (cation) can also reduce the anion gap (Pandey 2021).
Remember that acid-base balance is a complex and dynamic process. For example, acids such as keto acids and lactic acid will be neutralized by bicarbonate. This will cause a decrease in bicarbonate and an increase in the anion gap. An increased anion gap suggests metabolic acidosis and further investigation is warranted.
References
Brubaker, Ross H., et al. “High Anion Gap Metabolic Acidosis.” StatPearls, StatPearls Publishing, 11 August 2021.
Pagana, Kathleen Deska; Pagana, Timothy J.; Pagana, Theresa N. Mosby's Diagnostic and Laboratory Test Reference. Elsevier Health Sciences. 2019.
Pandey, Devansh G. and Sandeep Sharma. “Biochemistry, Anion Gap.” StatPearls, StatPearls Publishing, 18 July 2021.