LIVING THE LAB LIFE
A BLOG FOR ASCLS REGION V
Last month, many news outlets featured a very buzzy story about a potentially breakthrough treatment for severe sepsis patients. The lead physician involved in the study treated his patients with a cocktail drug combination of vitamins and corticosteroids, with the principle ingredient of vitamin C. Now, much more research will need to be done to determine whether this treatment is truly the next breakthrough in severe sepsis care or just another fluke study that does not work out in follow-up studies. But if this treatment were to become standard in hospitals across the country, where would that leave us in the laboratory?
Vitamin C (ascorbic acid) is a water-soluble vitamin, meaning the body absorbs whatever is can use and the excess is excreted in urine. It is a reducing agent (anti-oxidant), meaning it gives up electrons to other molecules, protecting them from damaging oxidation. In 1928, Albert Szent-Gyorgi first isolated Vitamin C. He would go on to win a Nobel Prize for his discovery.
Vitamin C deficiency, or scurvy, is rare in the modern world where access to vitamin C rich foods (vegetables and citrus fruits) is high. Most patient who present with scurvy are malnourished due some other condition, such as alcoholism. Symptoms include bleeding gums, skin hemorrhages, fatigue, . Most people get more vitamin C in their diets than they can use.
There are many methodologies available to measure vitamin C concentration, including capillary electrophoresis, spectrophotometric, and enzymatic methods. HPLC systems have come into favor in recent years due to their improved sensitivity and specificity. Serum or whole blood specimens can be used to measure vitamin C. Overall, the demand for vitamin C testing is low, due to the rarity of deficiency in first-world nations.
Vitamin C has been shown to cause false-negative results in guaiac-based testing. Increased levels of vitamin C have also been implicated in false-negative glucose, nitrite, and occult blood results in urine macroscopic dipstick results. In the case of occult blood, this happens because Vitamin C reacts with the hydrogen peroxide in the test strip. Once this happens, the hydrogen peroxide is removed from the equation and the chromogen cannot be oxidized. Some manufacturers have eliminated this issue by adding a layer of iodate to test strips which oxidizes Vitamin C, therefore eliminating the potential for interference. Additionally, vitamin C is an oxalate precursor, so high levels in urine can cause the formation of calcium oxalate crystals.
Vitamin C is a well-known agent of interference in laboratory testing. For this reason, it is essential for laboratory personnel to communicate with the patient care team about potential limitations in testing for patients being treated with high doses of Vitamin C.
Brunzel, N. A. (2013). Fundamentals of Urine & Body Fluid Analysis (3rd ed.). St. Louis, Missouri: Elsevier Saunders.
Clarke, W. (Ed.). (2011). Contemporary Practice in Clinical Chemistry (2nd ed.). Washington DC: AACC Press.
Harris, R. (2017, March 23). Doctor Turns Up Possible Treatment for Deadly Sepsis. Retrieved March 24, 2017, from NPR: http://www.npr.org/sections/health-shots/2017/03/23/521096488/doctor-turns-up-possible-treatment-for-deadly-sepsis
Scurvy. (2016, November 3). (Healthgrades Operating Company, Inc.) Retrieved March 31, 2017, from Healthgrades: https://www.healthgrades.com/conditions/scurvy