To diagnose pernicious anemia, several laboratory tests are used:
Key Laboratory Tests for Pernicious Anemia
1. Vitamin B12 Level:
This is the primary test to check for vitamin B12 deficiency. However, serum B12 levels alone may not be sufficient due to poor sensitivity and specificity. Levels below 200 pg/mL typically iindicate deficiency, but borderline results (200-400 pg/mL)
may require further testing.
2. Methylmalonic Acid (MMA):
The MMA test is often performed alongside other tests to confirm vitamin B12 deficiency. Elevated MMA levels (typically above 0.40 nmol/mL) suggest a deficiency, particularly when serum B12 levels are borderline or low.
3. Intrinsic Factor Antibodies (IFA): This test checks for antibodies against intrinsic factoror, a protein necessary for vitamin B12 absorption. A positive result is highly specific
factor for pernicious anemia, but sensitivity is lower, with only 40-60% of patients testing positiv
4. Parietal Cell Antibodies (PCA): About 90% of patients with pernicious anemia will have these antibodies. However, this test has low specificity, as it can also be positive in healthhy individuals and those with other autoimmune diseases.
5. Complete Blood Count (CBC):
A CBC is often performed to assess overall blood health. It can reveal macrocytic anemia, which is common in vitamin B12 deficiency, but not all patients will show this.
6. Serum Gastrin Levels:
Elevated gastrin levels can support the diagnosis of pernicious anemia, especially in patients
who test negative for intrinsic factor antibodies but still show symptoms of B12 deficiency.
7. Accurate diagnosis of pernicious anemia
A delay in treatment can lead to reversible neurological damage. It is recommended to avoid
vitamin B12 supplementation for at least 72 hours before testing to ensure accurate results.
8. Importance of Accurate Testing
Diagnosing pernicious anemia involves a combination of test to assess vitamin B12 status,the presence of specific antibodies, and overall blood health.