Most sensitive and specific test to diagnose iron deficiency anemia is:

Serum ferritin levels is the most sensitive and specific test to diagnose iron deficiency anemia Under steady-state conditions, the serum ferritin level correlates with total body iron stores; thus, the serum ferritin level is the most convenient laboratory test to estimate iron stores. The normal value for ferritin varies according to the age and gender of the individual.As iron stores are depleted, the serum ferritin falls to <15 mg/L. Such levels are diagnostic of absent body iron stores. Adult males have serum ferritin levels that average ~100 mg/L, corresponding to iron stores of ~1 g. Adult females have lower serum ferritin levels averaging 30 mg/L, reflecting lower iron stores (~300 mg). Ferritin is also an acute-phase reactant and, in the presence of acute or chronic inflammation, may rise several-fold above baseline levels.