Association of vitamin B12/folate and VVS
We compared serum levels of vitamin B12, folate, homocysteine and TSH, and the prevalence of vitamin B12 and folate deficiency between the study groups in Table 2. There was no statistically significant difference between the patients and the controls regarding the abovementioned parameters (Table 2). Although the difference in the prevalence of vitamin B12 deficiency was not statistically significant between patients with frequent and infrequent VVS [8/28 (28.6%) versus 2/16 (12.5%); P=0.283], this difference may be of clinical significance and reach statistical significance with a larger sample (OR=2.80, 95% CI: 0.52 to 15.23; P=0.233; Table 2).
We found that the serum level of vitamin B12 was remarkably lower in patients with frequent VVS compared to patients with infrequent VVS [233.8 (80.7) versus 305.2 (118.1) pg/mL; P=0.042]. This difference remained significant after considering possible confounders, including age, sex, and TSH (Table 3). The linear regression model for predicting serum level of vitamin B12 in the case group demonstrated that patients with frequent VVS were more likely to have lower serum vitamin B12 than patients with infrequent VVS (coefficient=-73.97, 95% CI: -138.54 to -9.40; P=0.026; Table 3).