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.