Is serum vitamin B(12) decrease a necessity for the diagnosis of subacute combined degeneration?: A meta-analysis

BACKGROUND: To determine the prevalence of subacute combined degeneration (SCD) patients with normal or elevated serum vitamin B(12) level and to identify clinical characteristics of these patients. METHODS: We searched PubMed, EMBASE, and Cochrane library, without language restriction up to June 2019 and included studies with SCD patients who were diagnosed with normal or elevated serum vitamin B(12) levels. Meta-analysis was performed to estimate the prevalence of SCD in patients with normal or elevated serum vitamin B(12) levels and compare the differences of clinical data between patients with low and no-low serum vitamin B(12) level. RESULTS: Six studies were included in our analysis, with a total number of 181 patients involved. The pooled proportion in patients with no-low serum vitamin B(12) level was 31.0% (95% confidence interval [CI]: 22.5–40.8). There was no significant difference in the level of hemoglobin (Mean difference (MD): –3.05, 95% CI: –12.42 to 6.33. P = 0.52) and erythrocyte mean corpuscular volume (MD: –2.37, 95% CI: –11.17 to 6.43, P = 0.60) between SCD patients with no-low and those with low serum vitamin B(12) levels. The meta-analysis showed that the functional disability rating scale on admission in patients with low serum vitamin B(12) level was no worse than that with normal or elevated serum vitamin B(12) level (MD: 0.29, 95% CI: –0.58 to 1.16, P = 0.51). CONCLUSION: Decreased level of serum vitamin B(12) may not be a necessity for the diagnosis of SCD. Approximately one third of the SCD patients have normal or elevated serum vitamin B(12) level. No differences were found in clinical severity between patients with normal or elevated serum vitamin B(12) level and those with low level of serum vitamin B(12) on admission.