From the Guidelines
To determine the etiology of metabolic acidosis, several laboratory tests beyond the basic metabolic panel are helpful, including urine organic acid analysis, which can aid in the diagnosis of organic acidemias, fatty acid oxidation disorders, and other metabolic disorders, as outlined in the 2018 update by the American College of Medical Genetics and Genomics 1. The anion gap calculation is essential as it divides metabolic acidosis into high anion gap and normal anion gap types.
- Serum lactate levels should be measured to identify lactic acidosis, which can result from tissue hypoperfusion, sepsis, or certain medications.
- Serum ketones help diagnose diabetic, alcoholic, or starvation ketoacidosis.
- Toxicology screens can detect substances like salicylates, methanol, ethylene glycol, or propylene glycol that cause toxic acidosis.
- Urine studies including pH, electrolytes, and urine anion gap assist in diagnosing renal tubular acidosis and evaluating renal acid excretion.
- Plasma osmolal gap helps identify ingestion of alcohols or glycols. Additional helpful tests include:
- Serum creatinine and BUN to assess kidney function
- Liver function tests to evaluate hepatic causes
- Medication review to identify drug-induced acidosis In specific cases, measuring:
- D-lactate (for short bowel syndrome)
- Pyruvate levels (for mitochondrial disorders)
- Or performing genetic testing for inherited metabolic disorders may be warranted, as certain disorders such as organic acidemias can be identified through urine organic acid analysis 1. These tests collectively provide a comprehensive evaluation to pinpoint the specific cause of metabolic acidosis, which is crucial for appropriate management.
From the Research
Helpful Labs to Determine Etiology of Metabolic Acidosis
To determine the etiology of metabolic acidosis, several labs can be helpful, including:
- Electrolyte panel to evaluate sodium, potassium, chloride, and bicarbonate levels 2
- Arterial blood gas (ABG) to assess pH, PaCO2, and PaO2 2
- Serum anion gap calculation to classify the disorder into normal (hyperchloremic) or elevated anion gap 2, 3
- Blood urea nitrogen (BUN) and creatinine to assess renal function 4, 5
- Glucose and ketone levels to evaluate for diabetic ketoacidosis 4, 5
- A1C to assess glucose control 4, 5
- Urinalysis to evaluate for ketones, glucose, and protein 4, 5
- Complete blood count (CBC) with differential to evaluate for infection or other conditions 4, 5
- Electrocardiography (ECG) to evaluate for cardiac complications 4, 5
- Amylase, lipase, hepatic transaminase levels, troponin, creatine kinase, blood and urine cultures, and chest radiography to evaluate for other conditions that may be contributing to metabolic acidosis 5
Specific Conditions
For specific conditions, additional labs may be helpful, such as: