There are many causes of low serum haptoglobin besides hemolysis, including1-4:
- Cirrhosis of the liver
- Disseminated ovarian carcinomatosis
- Pulmonary sarcoidosis
- Elevated estrogen states
- Repetitive physical exercise
- Blood transfusions
- Drugs (eg, oral contraceptives, chlorpromazine, indomethacin, isoniazid, nitrofurantoin, quinidine, and streptomycin)
- Iron deficiency anemia
- Megaloblastic anemia (by destruction of megaloblastic RBC precursors in the bone marrow)
- Congenital causes
Less well-known is that congenital haptoglobin deficiency (“anhaptoglobinemia”) may not be so rare in the general population at a prevalence of 1% among whites and 4% among African-Americans (>30% in blacks of West African origin)3. Measurement of serum hemopexin, another plasma protein that binds heme, may help distinguish between this condition and acquired hypohaptoglobinemia— in the absence of hemolysis, hemopexin levels should remain unchanged3,5.
Final Fun Fact: Did you know that serum haptoglobin is often low during the first 6 months of life?
- Shih AWY, McFarane A, Verhovsek M. Haptoglobin testing in hemolysis: measurement and interpretation. Am J Hematol 2014;89: 443-47. https://www.ncbi.nlm.nih.gov/pubmed/24809098
- Sritharan V, Bharadwaj VP, Venkatesan K, et al. Dapsone induced hypohaptoglobinemia in lepromatous leprosy patients. Internat J Leprosy 1981;307-310. https://www.ncbi.nlm.nih.gov/pubmed/7198620
- Delanghe J, Langlois M, De Buyzere M, et al. Congenital anhaptoglobinemia versus acquired hypohaptoglobinemia. Blood 1998;9: 3524. http://www.bloodjournal.org/content/bloodjournal/91/9/3524.full.pdf
- Haptoglobin blood test. https://medlineplus.gov/ency/article/003634.htm. Accessed August 6, 2017.
- Smith A, McCulloh RJ. Hemopexin and haptoglobin: allies against heme toxicity from hemoglobin not contenders. Front. Physiol 2015;6:187. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4485156/pdf/fphys-06-00187.pdf
In collaboration with Kris Olson, MD, MPH, Mass General Hospital, Boston, MA