Certified Neuroscience Registered Nurse (CNRN) Practice Exam

Disable ads (and more) with a membership for a one time $2.99 payment

Prepare for the CNRN Exam. Test your knowledge with our comprehensive multiple-choice questions and detailed explanations. Boost your confidence and improve your chances of a successful exam outcome!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

What lab test is often used to diagnose vitamin B12 deficiency?

Complete blood count
Serum ferritin
Methylmalonic acid level
Reticulocyte count

The correct answer is: Methylmalonic acid level

The diagnosis of vitamin B12 deficiency is frequently confirmed by measuring the level of methylmalonic acid (MMA) in the serum. In conditions of vitamin B12 deficiency, the metabolism of certain fatty acids is impaired, leading to an accumulation of MMA. Elevated levels of methylmalonic acid are a reliable indicator of a deficiency in vitamin B12, making this lab test particularly useful when assessing individuals suspected of having this nutritional deficiency. While a complete blood count can show signs related to anemia, and reticulocyte counts can indicate bone marrow response, they do not specifically point to B12 deficiency. Serum ferritin is generally used to assess iron stores and does not provide information about vitamin B12 levels. Thus, measuring methylmalonic acid serves as a direct and effective method for diagnosing vitamin B12 deficiency.