Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (789 page)

   Following exercise

   Methylene chloride toxicity (found in paint removers)

   Limitations

   COHB diminishes at a rate of about 15% per hour when the patient is removed from the contaminated environment.

   The most common cause of CO toxicity is exposure to automobile exhaust fumes. Significant levels of COHB can also be observed in heavy smokers. Victims of fires often show elevated levels from inhaling CO generated during combustion.

   Susceptibility to CO poisoning is increased in anemic persons.

CARCINOEMBRYONIC ANTIGEN (CEA)

   Definition

   CEA is a glycoprotein normally produced only during early fetal life and rapid multiplication of epithelial cells, especially those of the digestive system. CEA also appears in the blood of chronic smokers. Less than 25% of patients with disease confined to the colon have elevated CEA. Sensitivity is increased with advancing tumor stage. CEA levels should be ordered only after malignancy has been confirmed. CEA levels typically return to normal within 4–6 weeks after surgical resection. Major role is in following patients for relapse after intended curative treatment. The American Society of Clinical Oncology recommends monitoring CEA levels every 2–3 months for at least 2 years in patients with stage II and III disease.

   
Normal values:
<2.5 ng/mL in nonsmokers; <5 ng/mL in smokers.

   Use

   Monitoring colorectal cancer and selected other cancers such as medullary thyroid carcinoma, cancers of the rectum, lung, pancreas, stomach, and ovaries

   May be useful in assessing the effectiveness of chemotherapy or radiation treatment

   Diagnosis of malignant pleural effusion