From the Research
Low haptoglobin levels are a significant indicator of intravascular hemolysis, and the most recent evidence suggests that they should be interpreted with caution, considering the potential for false positives and negatives, as well as the impact of inflammatory conditions on haptoglobin levels. When red blood cells rupture, they release hemoglobin, which binds to haptoglobin, depleting its levels as the complexes are rapidly cleared by the liver 1. Common causes of low haptoglobin include hemolytic anemias, such as autoimmune hemolytic anemia, which can be diagnosed using the direct antiglobulin test, and subclassified based on the thermal range of the antibody 2, 3.
Some key points to consider when interpreting low haptoglobin levels include:
- The potential for false positives due to improper specimen preparation, cirrhosis, elevated estrogen states, and hemodilution 4
- The potential for false negatives due to hypersplenism and medications such as androgens and corticosteroids 4
- The impact of inflammatory conditions on haptoglobin levels, which can sometimes mask hemolysis by elevating haptoglobin levels that would otherwise be low 4
- The importance of further testing, including a complete blood count, peripheral blood smear, reticulocyte count, and direct Coombs test, to determine the underlying cause of low haptoglobin levels 1
In clinical practice, it is essential to consider the most recent and highest-quality evidence when interpreting low haptoglobin levels, and to approach each case with a systematic and cautious approach, considering the potential for false positives and negatives, as well as the impact of inflammatory conditions on haptoglobin levels. Treatment should focus on addressing the underlying cause of low haptoglobin levels, rather than the low levels themselves, and may involve medications such as corticosteroids, rituximab, or splenectomy, depending on the specific diagnosis and clinical context 2, 3.