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?
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- 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
Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Massachusetts General Hospital, Harvard Catalyst, Harvard University, its affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!