Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (974 page)

   
Normal range
(adults): 37–47% for women and 42–52% for men.

   Interpretation

   Abnormalities in Hct levels parallel those for Hb.

   Limitations

   Errors may occur in patients with polycythemia vera, as well as in those with very high WBC counts because of an elevated buffy coat, with RBC agglutination, and with large platelets. These errors are more marked in the manual methods.

   Errors in both methodologies may also occur in patients with abnormal plasma osmotic pressure. Such errors are minimized with the current generation machines.

   Technical errors in blood preparation may also result in false values (see “Hemoglobin” below). In blood kept at room temperature for more than 6 hours, the Hct and MCV are elevated due to swelling of RBCs, whereas cell counts and indices are stable for 24 hours.

HEMOGLOBIN (Hb)
^†

   Definition

   Hb is the respiratory protein of RBCs, consisting of 3.8% heme and 96.2% globin. There are more than 800 variants due to mutations in the globin molecule.

   
Normal range
(adults): 12–16 g/dL in women and 14–18 g/dL in men.

   Use

   Hb is of great utility in detecting anemias or erythrocytosis.

   Interpretation