Albumin-to-Globulin (A/G) Ratio: Clinical Meaning and Normal Values
The normal A/G ratio ranges from approximately 1.2 to 2.2, calculated by dividing serum albumin by serum globulin (total protein minus albumin), and serves as a marker of protein metabolism abnormalities, liver dysfunction, and systemic disease. 1
What the A/G Ratio Represents
The A/G ratio reflects the balance between albumin production (primarily by the liver) and globulin levels (immunoglobulins and other proteins). 1
- In liver disease, the ratio decreases because hepatic dysfunction causes reduced albumin synthesis while globulins increase compensatorily. 1, 2
- The ratio provides insights into liver function even when individual protein values remain within normal ranges, making it valuable for detecting subtle protein metabolism abnormalities. 1
Normal Reference Values
The normal A/G ratio is typically 1.2 to 2.2, though specific cutoffs vary by clinical context:
- Values below 1.2 are associated with increased mortality risk in heart failure patients. 3
- Values below 1.18 predict worse outcomes in hepatocellular carcinoma. 4
- Values below 1.38 are associated with increased 1-year mortality in chronic heart failure. 3
Clinical Applications
Liver Disease Assessment
- The A/G ratio is valuable in liver disease evaluation, as hepatic dysfunction causes decreased albumin production with compensatory globulin increases. 1
- In hepatic diseases, globulin rise with reduced albumin occurs in 72.3% of cases, compared to only 32.3% in non-hepatic systemic diseases. 2
Kidney Disease Context
- The A/G ratio provides additional information about protein metabolism when used alongside albumin-to-creatinine ratio and estimated glomerular filtration rate (eGFR). 1
- Low A/G ratios are associated with vascular adverse events in kidney disease patients. 1, 5
Prognostic Value
- Low A/G ratio is an independent predictor of mortality in chronic heart failure, colorectal cancer, and hepatocellular carcinoma. 3, 6, 4
- The ratio functions as a continuous risk marker, with lower values indicating worse prognosis. 3, 6
Important Interpretation Considerations
Factors Affecting the Ratio
- Hydration status affects both albumin and globulin, so the ratio may provide more stable information than individual values. 1
- Thyroid function influences albumin metabolism: hyperthyroidism potentially lowers A/G ratio while hypothyroidism may increase it. 1
- Body mass index is inversely associated with albumin levels, potentially affecting the ratio in obese patients. 7
Clinical Context Requirements
- The A/G ratio should be interpreted alongside other laboratory and clinical findings, considering age, sex, and comorbidities. 1
- In nephrotic syndrome, both albumin and globulins may be decreased, making the ratio less reliable without additional context. 1
- The ratio remains clinically significant even when serum albumin is normal (>3.5 g/dL), as patients with higher A/G ratios within the normal albumin range have better survival. 6
When A/G Ratio is Severely Abnormal
An A/G ratio of 0.4 or lower indicates severe protein dysregulation requiring immediate comprehensive evaluation: