Diagnostic accuracy of reticulocyte hemoglobin content in Thai patients with microcytic red cells as a test for iron deficiency anemia

Background: Reticulocyte hemoglobin content (CHr) is helpful for early diagnosis of iron deficiency anemia (IDA). However, its use is limited in thalassemia carriers. Objectives: To determine the accuracy of CHr and reticulocyte count as a test for iron deficiency anemia in Thai patients with microcytic red cells given the high prevalence of thalassemia carriers in Thailand. Methods: Thai patients with adult microcytic anemia (mean corpuscular volume <= 80 fL) were prospectively enrolled. We conducted an automated complete blood count, reticulocyte count (with CHr), ferritin, and hemoglobin analysis. IDA was defined by a ferritin reference level <50 mu g/L and >= 1 g/dL response within a month to iron dietary supplement. Cutoff points were determined from receiver operating characteristic curves. Results: We included 168 patients (53 with IDA, 50 with anemia of inflammation (AI), 49 with thalassemia traits, and 16 with thalassemia diseases) and 99 healthy controls. The CHr in patients with IDA and thalassemia disease were significantly less than those in patients with AI and thalassemia trait (P < 0.001), who in turn had lower CHr compared with normal controls (P < 0.001). Patients with thalassemia were distinguished by their high reticulocyte counts. After excluding thalassemia, a cutoff CHr <27.0 pg showed a sensitivity of 84.9% and specificity of 77.8% for IDA diagnosis. Additionally, mean corpuscular hemoglobin concentration (MCHC) <31.6 g/dL showed a sensitivity of 81.1% and specificity of 83.7% for IDA diagnosis. Conclusions: CHr combined with additional information about reticulocyte count and MCHC is useful for diagnosis of IDA in Thais.