Wallach's Interpretation Of Diagnostic Tests: Pathways To Arriving At A Clinical Diagnosis - Plot & Excerpts
Normal hemoglobin (Hb) range is established by population studies, but range should be adjusted for different age groups, especially for children, and levels are lower in women and in African Americans. There is some debate whether people of older ages have physiologically lower Hg levels. Most likely lower values reflect underlying pathology. Hb values are more accurate than hematocrit (Hct) values, because Hb is measured directly by automated analyzers, whereas the Hct is a calculated value. Diagnosis There are many ways to classify anemias, but the differential diagnosis of anemia can be narrowed by using the RBC size, as reflected in the MCV and the reticulocyte count. See Figure 9-1. In addition, insight into mechanism and etiology complements the differential diagnosis. Onset of anemia has a great impact on symptoms and diagnosis.Figure 9–1 Workup of anemias based on the mean corpuscular volume (MCV).Onset Acute Bleeding Hemolysis Acute bone marrow disease (e.g., leukemias) Chronic Deficiencies: iron (most common), folic acid, vitamin B12, nutritional Congenital (hemoglobinopathies, hereditary spherocytosis) Neoplasia, especially metastatic or hematologic malignancies Renal disease Chronic inflammatory disorders Many othersWhen to Suspect Anemia Children Young child who fails to thrive and is not as active as expected for age. Anemia detected at ages 3−6 months suggests a congenital disorder of Hb synthesis or structure. Adults. Nonspecific symptoms and signs such as weakness, dizziness, progressive lack of energy, pallor, and shortness of breath in the absence of serious heart or lung disease (overt CHF may develop as a consequence of severe anemia). Protracted GI or vaginal bleeding. A family history of anemia. Jaundice or red urine. Laboratory Findings Initial laboratory investigation should include a complete CBC with a reticulocyte count and examination of the peripheral blood smear (PBS).
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