Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (839 page)

   Heavy smokers: >2 packs/day: 8–9%

Methemoglobin

   This is produced by the oxidation of the normal ferrous iron of Hb to ferric iron, making it chemically useless for respiration.

   A small amount of methemoglobin is normally present in blood, but the conversion of a larger fraction of hemoglobin into methemoglobin results in perceptible cyanosis. Methemoglobinemia may be acquired anytime in life by exposure to a number of different chemical agents, such as nitrites, or it may be congenital due a genetic condition.

   
Normal:
0.06–0.24 g/dL.

COPPER

   Definition

   Copper is a metal component of various enzymes (e.g., cytochrome oxidase, superoxide dismutase, tyrosinase) involved in Hb synthesis, bone and elastic tissue development, and CNS function. Copper test levels need to be evaluated and compared to ceruloplasmin levels.

   
Normal range:
see Table 16.23.

TABLE 16–23. Normal Levels of Serum Copper

   Use

   Aids in the diagnosis of Wilson disease

   Assessment of primary biliary cirrhosis

   Assessment of primary sclerosing cholangitis

   Interpretation