34 HEMOGLOBIN, HEMATOCRIT, MCV (mean corpuscular volume), MCH (mean corpuscular hemoglobin), MCHC (mean corpuscular hemoglobin concentration)
Description
This article is from the Interpretation Of Lab Test Profiles, by Ed Uthman uthman@neosoft.com with numerous contributions by others.
34 HEMOGLOBIN, HEMATOCRIT, MCV (mean corpuscular volume), MCH (mean corpuscular hemoglobin), MCHC (mean corpuscular hemoglobin concentration)
Strictly speaking, anemia is defined as a decrease in total body red
cell mass. For practical purposes, however, anemia is typically defined
as hemoglobin <12.0 g/dL and direct determination of total body RBC
mass is almost never used to establish this diagnosis. Anemias are then
classed by MCV and MCHC (MCH is usually not helpful) into one of the
following categories:
A. Microcytic/hypochromic anemia (decreased MCV, decreased
MCHC)
Iron deficiency (common)
Thalassemia (common, except in people of Germanic,
Slavonic, Baltic, Native American, Han Chinese,
Japanese descent)
Anemia of chronic disease (uncommonly microcytic)
Sideroblastic anemia (uncommon; acquired forms more often
macrocytic)
Lead poisoning (uncommon)
Hemoglobin E trait or disease (common in Thai, Khmer,
Burmese,Malay, Vietnamese, and Bengali groups)
B. Macrocytic/normochromic anemia (increased MCV, normal MCHC)
Folate deficiency (common)
B12 deficiency (common)
Myelodysplastic syndromes (not uncommon, especially in
older individuals)
Hypothyroidism (rare)
C. Normochromic/normocytic anemia (normal MCV, normal MCHC)
The first step in laboratory workup of this broad class of
anemias is a reticulocyte count. Elevated reticulocytes implies
a normo-regenerative anemia, while a low or "normal" count
implies a hyporegenerative anemia:
1. Normoregenerative normocytic anemias (appropriate
reticulocyte response)
Immunohemolytic anemia
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
(common)
Hemoglobin S or C
Hereditary spherocytosis
Microangiopathic hemolytic anemia
Paroxysmal hemoglobinuria
2. Hyporegenerative normocytic anemias (inadequate
reticulocyte response)
Anemia of chronic disease
Anemia of chronic renal failure
Aplastic anemia*
*Drugs and other substances that have caused aplastic anemia include
the following:
amphotericin sulfonamides phenacetin trimethadione silver chlordiazepoxide tolbutamide thiouracil carbamazepine chloramphenicol tetracycline oxyphenbutazone arsenicals chlorpromazine pyrimethamine carbimazole acetazolamide colchicine penicillin aspirin mephenytoin bismuth promazine quinacrine methimazole chlorothiazide dinitrophenol ristocetin indomethacin phenytoin gold trifluoperazine carbutamide perchlorate chlorpheniramine streptomycin phenylbutazone primidone mercury meprobamate chlorpropamide thiocyanate tripelennamine benzene
The drugs listed above produce marrow aplasia via an unpredictable,
idiosyncratic host response in a small minority of patients. In
addition, many antineoplastic drugs produce predictable, dose-related
marrow suppression; these are not detailed here.
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