Reticulocyte Hemoglobin as a Screening Test for Iron Deficiency Anemia: A New Cut-Off

**Background:** Latent iron deficiency (LID) is a condition where body iron stores are depleted without manifest anemia, often going unrecognized. Reticulocyte hemoglobin content (Ret-Hb) directly reflects the iron available for heme synthesis in erythroblasts and has been proposed as an efficient marker of iron status. Current Ret-Hb cutoffs for diagnosing iron deficiency and IDA vary considerably across studies (25–29 pg for iron deficiency, ~21 pg for IDA). This study aimed to assess Ret-Hb's utility in detecting LID and as a screening parameter for IDA.

**Methods:** A cross-sectional study was conducted at Najran University Hospital, Saudi Arabia, involving 108 randomly selected individuals from internal medicine outpatient clinics: 64 with IDA and 44 with normal hemoglobin levels. Anemia was classified per WHO definitions (Hb < 12.0 g/dL in females, < 13.0 g/dL in males). Iron deficiency was defined as transferrin saturation < 20% and serum ferritin < 100 ng/mL. A serum ferritin < 30 ng/mL with normal Hb indicated insufficient iron stores. Patients with hereditary hematological disorders, hematological malignancies, cancer, or those on long-term chemotherapy/radiotherapy were excluded; pregnant women were also excluded. Blood samples were collected in K3EDTA tubes and analyzed using Sysmex XS 500i for CBC and Ret-Hb, and COBAS C311 for serum iron and ferritin. Statistical analysis used IBM SPSS 20 with independent sample t-tests and ROC curve analysis; significance was set at p < 0.05.

**Key Results:** IDA patients showed significantly (p < 0.05) decreased levels of hemoglobin, MCV, MCH, MCHC, serum iron, and ferritin, along with significant increases in RDW and platelet count compared to normal individuals. There was a highly significant decrease in Ret-Hb in anemic patients of both sexes (p = 0.0001) compared to non-anemic patients, while reticulocyte count showed no significant difference. In individuals with normal hemoglobin, Ret-Hb was significantly decreased in males with low ferritin levels and showed a tendency to decrease in females. Male IDA patients showed significant decreases in Ret-Hb, RBCs, Hb, MCHC, and serum iron but no significant difference in MCV, MCH, RDW, PLT, UIBC, ferritin, or RC compared to normal-Hb individuals with low ferritin. Female IDA patients showed significant decreases in Ret-Hb, RBCs, Hb, MCV, MCH, MCHC, serum iron, and ferritin, and significant increases in RDW, PLT, and UIBC, without significant difference in RC. Ret-Hb showed positive correlations with hemoglobin (p = 0.0001, r = 0.819) and serum ferritin (p = 0.0001, r = 0.540), and tended to correlate with serum iron (p = 0.065, r = 0.232). ROC analysis identified a Ret-Hb cutoff of 21.2 pg (100.0% sensitivity, 64.1% specificity) for predicting IDA.

**Clinical Implications:** The study supports Ret-Hb measurement as a useful screening test for IDA, with a cutoff of 21.2 pg providing 100% sensitivity. Ret-Hb offers advantages over traditional markers: it is less influenced by inflammation than ferritin and transferrin, and less affected by diurnal variation or food intake than serum iron. The authors note that the lower cutoff compared to some studies (e.g., 29.3 pg with 90.6% sensitivity, 66.7% specificity in another study) reflects their choice of 100% sensitivity for screening purposes. Ret-Hb may be particularly valuable for detecting LID in males, where significant decreases were observed even with normal hemoglobin. The study's limitations include the small sample size from a single center, exclusion of pregnant women and chronic disease patients, and lack of evaluation of soluble transferrin receptor and other markers. Further research with larger, more diverse populations is needed to validate these findings.