Platelet levels before and after iron replacement therapy in patients with iron deficiency anemia.

Background: Iron deficiency anemia (IDA) is the most common cause of anemia worldwide. Patients with IDA often present thrombocytosis, but little is known about its degree and prevalence, and its response to iron replacement.

Methods: We conducted a retrospective review of 76 consecutive patients with anemia secondary only to iron deficiency. Laboratory data were collected both at baseline and at 3 months after either oral or intravenous iron replacement therapy. We defined thrombocytosis as a platelet count >400 × 10⁹/L.

Results: The median age of the patients was 54 years (range, 22-90 years), and 59 of 76 (78%) patients were females. The replacement therapy consisted of oral iron (n = 13), intravenous iron (n = 33), or both (n = 30). The median Hb and ferritin levels at baseline and at 3 months after the iron replacement were 9.9 g/dL and 18 mg/dL, and 12.4 g/dL (p < 0.0001) and 113 mg/dL (p < 0.0001), respectively. Thrombocytosis before and after the iron administration was present in 17 (22%) and 4 (5%) patients, respectively. Regardless of thrombocytosis, the platelet count decreased in 55 (72%) patients. The median platelet level at baseline and at 3 months after the iron replacement was 299 (95% CI, 276-330) and 265 (95% CI, 245-295) × 10⁹/L (p < 0.0001), respectively.

Conclusion: Thrombocytosis is found in about one fifth of patients with IDA at baseline, and it is expected to resolve within 3 months of iron replacement therapy in most of them. Iron administration is associated with a decrease of the platelet counts, even in the absence of preexisting thrombocytosis.