The nurse has just admitted a 35-year-old female client who has a serum B12 concentration of 800 pg/ml. Which of the following laboratory findings would cue the nurse to focus the client’s history on the specific drug or alcohol abuse?
A. Total bilirubin, 0.3 mg/dL
B. Serum creatinine, 0.5 mg/dL
C. Hemoglobin, 16 g/dL
D. Folate, 1.5 ng/mL
Correct Answer: D. Folate, 1.5 ng/mL
The normal range of folic acid is 1.8 to 9 ng/mL, and the normal range of vitamin B12 is 200 to 900 pg/mL. A low folic acid level in the presence of a normal vitamin B12 level is indicative of a primary folic acid-deficiency anemia. Factors that affect the absorption of folic acid are drugs such as methotrexate, oral contraceptives, antiseizure drugs, and alcohol.
Option A: The total bilirubin levels are normal. The liver is the major storage organ for folate, which undergoes several reactions before exit to both the biliary and systemic blood circulation. 5-MTHF crosses the basolateral membranes of hepatocytes after its transport through the intestine to the portal vein.
Option B: The serum creatinine levels are normal. Urinary folate excretion is governed by renal tubular cell re-absorption by way of both FBP and RFC on proximal tubular cell brush border membranes. However, long term ethanol exposure in a micro pig model of ALD had no effect on folic acid transport by isolated renal tubular brush border membranes or on the expression of renal tubular RFC
Option C: The hemoglobin values are within normal limits. Chronic alcoholics typically present with reduced vitamin B6 levels, which has been attributable to displacement of the vitamin from its protein carrier by acetaldehyde with subsequent degradation by phosphatases.
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