The assessment of reticulocyte and erythrocyte haemoglobin contents, and their use in the evaluation of iron status in hospitalised patients

Current clinical practice relies on sufficiently low haemoglobin (HB) level, low serum ferritin (SF), low serum iron concentration and an elevated total iron binding capacity (TIBC) to identify iron deficiency (ID) and iron deficiency anaemia (IDA). However, these parameters are sometimes not reliable in assessing iron status in patients with underlying conditions like chronic diseases, malignancies and inflammation. Growing evidence indicates the appropriate inclusion of reticulocyte haemoglobin content (RET-He) and red cell haemoglobin content (RBC-He) into the iron studies investigation could improve the early diagnosis. The aim of this study were to evaluate the extent to which RET-He and RBC-He values could improve the assessment of iron status in chronic disease and inflammation, and to evaluate if the inclusion could be used to preclude the need for further biochemical assessment in iron status.
A total of 800 samples (89 normal, 611 patients and 100 haemochromatosis) were obtained and analysed for biochemical and haematological iron indicators. RET-He and RBC-He were added to the full blood counts parameters on the Sysmex XE2100TM, and C-reactive protein was added to indicate inflammation. The inclusion criteria were based on symptomatic and asymptomatic cases, such as gastroenterological, cancer and rheumatoid arthritis. Children and pregnant women were excluded from participating in the study. Stability of RET-He, RBC-He, HB, mean cell volume (MCV) and mean cell haemoglobin (MCH) were evaluated to determine if there was significant shift in the result over 96 h and at varying temperature 40C, 200C and 300C. RET-He and RBC-He were also added to the haematological iron assessment in the follow up monitoring of haemochromatosis patients to evaluate their usefulness.
The serial measurement shows reasonable stability for MCH, HB, RET-He and RBC-He for up to 96 h. Elevated shift were recorded for MCV on all the samples in the same time frame. Receiver operating characteristic (ROC) analysis was used to obtain sensitivity and specificity of the biochemical and haematological iron indices measured in the study. Female patients were classified into ID using SF ≤ 20 ng/mL. The area under the curve (AUC) in this group were (SF = 0.99 versus RET-He and RBC-He = 0.72). RET-He has (sensitivity, 89.6% and specificity, 58.0%), and RBC-He, (sensitivity 88.6% and specificity 57.0%) in detecting ID. Female patients with IDA were classified using HB ≤ 11.5 g/dL. The AUC were (HB = 0.99; versus RET-He = 0.87 and RBC-He = 0.86). RET-He has (sensitivity, 84.0% and specificity, 72.0%) and RBC-He (sensitivity 82.0% and specificity 71.0%) versus HB (sensitivity, 100.0% and specificity, 99.9%) in detecting IDA. In male patients with ID, SF < 20 ng/mL was used for classification, AUC were (SF = 1.00 versus RET-He = 0.78 and RBC-He = 0.79). RET-He has (sensitivity, 78.4% and specificity, 66.0%) and RBC-He (sensitivity 80.0% and specificity 61.2%), against SF (sensitivity, 100.0% and specificity, 100.0%) in detecting ID. In male patients with IDA, HB <13.5 g/dL was used for classification, AUC were (HB = 0.99 versus RET-He = 0.89 and RBC-He = 0.87). RET-He has (sensitivity, 88.6% and specificity, 83.0%) and RBC-He (sensitivity 83.8% and specificity 80.0%) in detecting IDA in male patients. Diagnostic plots were used to assess the ability of RET-He and RBC-He in comparison to other biochemical and haematological parameters, RET-He and RBC-He emerged as possible predictors of ID and IDA in inflammations and chronic diseases. The results of RET-He and RBC-He when measured with the other haematological parameters in the follow up treatment of haemochromatosis patients, shows 99% agreement with HB, MCV and MCH.
In conclusion, the inclusion of RET-He and RBC-He into the iron studies investigation may improve the identification of ID and IDA in chronic disease and inflammation, and can possibly detect changes in the cohort of cells with inadequate haemoglobinisation. Therefore, both indices hold promise as an alternative to biochemical iron studies especially, in patients with acute phase response and chronic diseases.