Vitamin B12 Testing in People With Suspected Vitamin B12 Deficiency

Key Messages

• Findings from 3 diagnostic accuracy studies indicate that individual tests are insufficient to diagnose vitamin B12 deficiency, and a testing strategy that uses homocysteine and methylmalonic acid should be used in individuals suspected or at risk of vitamin B12 deficiency. This is supported by a health technology assessment that concluded that the current evidence does not provide enough information to determine the most appropriate test, or combination of tests to use in these patients.
• The patient populations varied in the primary studies included in the systematic reviews and in the primary studies identified in this review, which may impact the generalizability of the results.
• Reference standards and cut-off values (i.e., thresholds) used to diagnose vitamin B12 deficiency varied in the primary studies. Presentation of units (e.g., pg/mL, pmol/L) also varied, making it difficult to compare results across studies.
• No studies were identified that evaluated the clinical utility of vitamin B12 testing in people with suspected vitamin B12 deficiency.
• No studies were identified that evaluated the cost-effectiveness of vitamin B12 testing in people with suspected vitamin B12 deficiency.
• No evidence-based guidelines were identified regarding the use of vitamin B12 testing in people with suspected vitamin B12 deficiency.