AG ratio with interpretation
Reading File
Quick answer
A/G ratio = Albumin ÷ Globulin
It is calculated from serum protein values:
[
\text{A/G ratio} = \frac{\text{albumin}}{\text{total protein} - \text{albumin}}
]
Typical reference range: about 1.0 to 2.2. Ranges vary by laboratory.
Interpretation
| A/G ratio | Possible interpretation |
|---|---|
| Low, <1.0 | Relatively low albumin or high globulins. Can occur with chronic liver disease, kidney protein loss, inflammation/infection, autoimmune disorders, malnutrition, or plasma-cell disorders such as multiple myeloma. |
| Normal, ~1.0-2.2 | Albumin and globulin levels are proportionate. Interpret along with the individual protein values and clinical context. |
| High, >2.2 | Usually reflects low globulins, such as in some immunodeficiency states. It may also occur with dehydration, though dehydration more often raises both protein fractions. |
Example:
Total protein = 7.0 g/dL; albumin = 4.2 g/dL
Globulin = 7.0 - 4.2 = 2.8 g/dL
Total protein = 7.0 g/dL; albumin = 4.2 g/dL
Globulin = 7.0 - 4.2 = 2.8 g/dL
[
A/G = 4.2/2.8 = 1.5
]
This is generally normal.
An abnormal A/G ratio is not diagnostic by itself. The albumin, total protein, liver and kidney tests, and sometimes serum protein electrophoresis are needed to determine the cause.
What if globulin is higher
Reading File
Quick answer
If globulin is higher than albumin, the A/G ratio becomes low, often less than 1.
Example:
- Albumin: 3.0 g/dL
- Globulin: 4.0 g/dL
- A/G ratio: 3.0 ÷ 4.0 = 0.75
This can happen for two broad reasons:
-
Globulin production is increased, commonly due to:
- Ongoing infection or inflammation
- Autoimmune diseases
- Chronic liver disease
- Some chronic infections
- Plasma-cell or lymphoid disorders, such as monoclonal gammopathy or multiple myeloma
-
Albumin is reduced, for example from:
- Liver disease or poor protein production
- Kidney or gut protein loss
- Malnutrition
- Severe inflammation
A mildly high globulin value can be temporary, such as during or after an infection. Persistent or significantly elevated globulin, especially with anemia, bone pain, recurrent infections, weight loss, kidney dysfunction, or a very low A/G ratio, should be assessed by a clinician. They may order serum protein electrophoresis (SPEP), immunofixation, and related blood tests to determine whether the increase is broad immune activity or a single abnormal protein.
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