Do all the patients with vitamin B12 deficiency have pernicious anemia?

BACKGROUND

Vitamin B12 deficiency may result in pernicious anemia (PA). This study evaluated whether all the patients with vitamin B12 deficiency had PA.

METHODS

The blood hemoglobin (Hb), iron, vitamin B12, folic acid, and homocysteine concentrations and mean corpuscular volume (MCV) in 90 vitamin B12-deficient patients were measured and compared with the corresponding data in 180 age- and sex-matched healthy control subjects. PA was defined by World Health Organization (WHO) as having an Hb concentration <13 g/dl for men and <12 g/dl for women, an MCV ≧ 100 fl, a serum vitamin B12 level <200 pg/ml, and serum gastric parietal cell antibody (GPCA) positivity.

RESULTS

We found that 35 (38.9%) and 20 (22.2%) patients with vitamin B12 deficiency had deficiencies of Hb (men <13 g/dl, women <12 g/dl) and iron (<60 μg/dl), respectively. Moreover, 65 (72.2%) and 37 (41.1%) patients with vitamin B12 deficiency had abnormally high blood homocysteine level (>12.7 μM) and high MCV (≧100 fl), respectively. In addition, 43 (47.8%) vitamin B12-deficient patients with had GPCA positivity. Patients with vitamin B12 deficiency had a significantly higher frequency of Hb or iron deficiency, of abnormally elevated blood homocysteine level or high MCV, and of GPCA positivity than healthy control subjects (all P-values < 0.001). However, only 17 (18.9%) of 90 vitamin B12-deficient patients were diagnosed as having PA by the WHO definition.

CONCLUSION

Only 18.9% of patients with vitamin B12 deficiency are discovered to have PA by the WHO definition.