Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (920 page)

Decreased In

   Inherited deficiency

   AML

   Liver disease

   Association with hypofibrinogenemia in obstetric complications such as DIC

   Presence of circulating inhibitors

FATTY ACIDS, FREE

   Definition

   Free fatty acids are formed by the breakdown of lipoprotein and triglycerides. All but 2–5% of the serum fatty acids are esterified. The “nonesterified” or “free” fatty acids are protein bound. Epinephrine, norepinephrine, glucagon, TSH, and ACTH release free fatty acids. Tumors producing such hormones cause release of excessive quantities of free fatty acids. Other names: nonesterified fatty acids (NEFA), FFA.

   
Normal range:

   Adults: 8–25 mg/dL or 0.28–0.89 mmol/L

   Children (or obese adults): <31 mg/dL or <1.0 mmol/L

   Use

   Monitoring nutritional status in the presence of malabsorption, starvation, and long-term parenteral nutrition.

   Valuable for the differential diagnosis of polyneuropathy when Refsum disease is suspected. In this disease, the enzyme that degrades phytanic acid is lacking.