Dear Editor:

Alinityhq (Abbott Diagnostics, Santa Clara, CA, USA) is a fully optical hematology analyzer that provides a complete blood count (CBC) with a 6-part white blood cell differential count, which includes the count of immature granulocytes (IGs). In addition, red blood cells (RBCs) and platelets can also be analyzed using the optical technology. With advances in optical technology and single cell analysis based on light scattered by isovolumetrically sphered RBCs, extended RBC parameters have become available. Advanced technology enables the measurement of the cellular hemoglobin (Hb) concentration in individual erythrocytes as well as measurement of the volume of erythrocytes. These parameters provide clinical utility for the screening and diagnosis of various anemic and certain other conditions and monitoring of treatment response [1-4]. For interpretation of the results, reliable reference ranges are needed. However, most published data include only Western population; thus, there is a lack of definitive data on Asian or Korean population. Additionally, due to differences in technology and lack of standardization, there is a difference between the values of these parameters measured using different instruments [5-8]. These differences imply that instrument-specific reference ranges are necessary for clinical diagnosis. Therefore, this study aimed to establish reference ranges for extended RBC parameters measured with the new Abbott hematology analyzer in Korean population.

This study enrolled 770 healthy individuals (413 men and 357 women) from Dong-A University Hospital. Peripheral blood samples were obtained during periodic health checks. All samples were analyzed using the new Abbott hematology analyzer. Blood was drawn into evacuated tubes containing K2-EDTA as anticoagulant and the tubes were kept at ambient temperature for no longer than 6 hours after blood collection. The data obtained were analyzed to identify the underlying normal distribution in men and women separately and the reference ranges were calculated as mean±2 standard deviations (SD). If no statistical difference was detected between the data obtained for men and women, then data of both the sexes were analyzed together. In cases of non-Gaussian distribution, non-parametric methods were used for analysis. For comparing results between gender and age groups, standard statistical methods were used in the MedCalc Statistical Software version 14.8.1 (MedCalc Software bvba, Ostend, Belgium). The results of the reference ranges for extended RBC parameters are shown in Table 1. The data distributions were considered to be Gaussian or non-Gaussian (non-parametric) depending on the parameters. Gaussian distributions were observed for hypochromic RBC and macrocytic RBC, while the remaining six parameters, including reticulocyte mean corpuscular volume (MCVr), reticulocyte mean corpuscular hemoglobin (MCHr), microcytic RBC, hyperchromic RBC, hemoglobin distribution width (HDW), and reticulocyte mean corpuscular hemoglobin concentration (MCHCr), exhibited non-Gaussian distribution. HDW and MCVr were identical for both the sexes. The values of the other parameters (microcytic RBC, hyperchromic RBC, MCHr, and MCHCr) were higher in men than in women, except for hypochromic RBC and macrocytic RBC.

Automated blood cell counters are becoming more sophisticated and the range of reportable parameters is ever increasing. Establishing reference ranges is the first step toward good laboratory practice and is essential for correct interpretation of laboratory results, which helps ensure that reliable results are reported to the clinician for decision-making. Procedures of how to establish reference intervals are described in international guidelines and recommendations [9, 10]. In the literature, only few authors have reported reference ranges for extended RBC and reticulocyte parameters, which are mainly based on data obtained from Western population [11, 12]. Previously, studies on the clinical usefulness of extended RBC and reticulocyte parameters measured using another hematology analyzer have been published; however, most of them have also evaluated on Western population [1-8]. There are also controversies over the reference ranges. Hoffmann et al. [11] described that there were no differences between women and men regarding the values of all extended RBC and reticulocyte parameters; however, in our study, we observed differences in all parameters except for HDW and MCVr. Moreover, in our study, the values of microcytic RBC, macrocytic RBC, hypochromic RBC, and hyperchromic RBC were higher, and those of HDW, MCVr, and MCHr were lower than the values reported in previous studies [11, 12]. Therefore, necessity for instrument- and population-specific reference ranges was confirmed.

However, the selection of healthy individuals as a reference group may be difficult when dealing with parameters that can be abnormal even in apparently healthy subjects. In order to circumvent these difficulties, we included subjects who were referred to a health care center for periodic health checks and in whom the incidence of disease is much lower than in patients. We also included a relatively wide range of age groups. However, we are not sure whether patients were completely excluded from the dataset because we had not reviewed the medical records of all subjects.

Both laboratory scientists and clinicians need to be up-to-date with new parameters and methods in hematology. Oftentimes, the laboratory scientists introduce new parameters and their clinical utility to the clinicians. In summary, we established reference ranges for extended RBC parameters measured with the new Abbott hematology analyzer in healthy Korean population. Our findings showed that there were statistically significant differences in reference values according to sex as well as ethnicity. Further studies specially focused on clinical usefulness of RBCs and RBC parameters in neonates, infants, and children are necessary.