Mal J Med Health Sci 14(SP3): 25-30, Dec 2018 25 Malaysian Journal of Medicine and Health Sciences (eISSN 2636-9346) ORIGINAL ARTICLE Usefulness of Red Blood Cell Size Factor (RSf) in Screening Genetic Variants of Alpha Thalassaemia Thalassaemia Trait Regardless of Iron Status Nur Juliana Idris 1,2 , Faridah Idris 2 , Zainina Seman 2 , Nik Hafidzah Nik Mustapha 1 1 Department of Pathology, Hospital Tuanku Ja’afar Seremban, 70300 Seremban, Negeri Sembilan, Malaysia 2 Department of Pathology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia ABSTRACT Introduction: Screening for alpha (α) thalassaemia trait (TT) is challenging especially in the presence of iron deficien- cy (ID). Red blood cell size factor (RSf) is a parameter introduced by Beckman Coulter capable of detecting acute and chronic changes to cellular haemoglobin status and iron supply. The research aimed to investigate the clinical usefulness of RSf as screening parameter for α TT and the effect of concomitant ID to RSf mean values (m.v) among respondents with α TT. Methods: A cross-sectional retrospective laboratory analysis involved 55 respondents’ data selected from January 2014 to December 2015 in Pathology Department, Hospital Tuanku Ja’afar Seremban, Negeri Sembilan. The significant difference at p <0.05 in the RSf m.v. among respondents with α 0 TT, α + TT, and ID groups and the effect concomitant ID to RSf m.v. were determined using statistical test, one-way analysis of variance (ANO- VA). Results: Significant differences were detected in RSf m.v. i) between α 0 TT, α + TT and ID, F (2, 52) = 18.99, p=0.001. ii) between α TT without ID, α TT with ID and ID cohorts for both a) α 0 TT [F (2, 33) = 23.77, p=0.001) and b) α + TT [F (2, 28) = 5.37, p=0.011]. iii) between α TT and ID group regardless of the presence of ID for both a) α 0 TT and b) α + TT. Conclusion: RSf is a potential screening parameter in evaluating patients with hypochromic microcyto- sis in identifying possible cases of alpha TT regardless of iron status. Keywords: Thalassaemia trait, Iron deficiency, Thalassaemia screening, Red blood cell indices Corresponding Author: Faridah Idris, MBBS, MPath Email: i_faridah@upm.edu.my Tel: +603-89472378 INTRODUCTION Iron deficiency is a common cause of microcytic anaemia affecting the global population particularly children and pregnant women (1). Being microcytic, thalassaemia trait (TT) usually resembles iron deficiency (ID) with or without anaemia in morphology. However, the underlying pathogenesis, treatment and prognosis of iron deficiency anaemia (IDA) and thalassaemia are entirely different. Since the early 1970s, automated full blood count (FBC) analysers have been used as initial screening tool to discriminate IDA and TT, partly because of its economical and practicality (2). Red blood cell (RBC) indices including mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and haemoglobin (Hb) concentration, are useful for thalassaemia screening. Unfortunately, none of these parameters is sufficiently reliable to identify the carrier status due to highly inaccurate predictors of globin genotype. Multiple cut off points have been reported to be useful for thalassaemia trait screening between 60-70 fL for MCV and 19-23 pg for MCH in α-TT detection, whereas only slight reduction is usually observed in α-TT (3). Quantification of HbA2 is recognised as an appropriate approach for screening and identifying classical beta thalassaemia trait. A Hb A2 cut-off level > 4.0% with MCV and MCH of <75 fl and <27 pg, respectively, were used as benchmark for screening and presumptive identification of classical beta thalassaemia carriers prior to deoxyribonucleic acid (DNA) studies (4). However, normal Hb A2 level does not exclude alpha (α) thalassaemia. A definitive diagnosis of α thalassaemia requires DNA analysis (3), however, is limited to research laboratories or specialist referral centres. Without conclusive diagnosis, some cases may be underdiagnosed, and unnecessary iron treatment may be given. Another important reason is to assist in the process of genetic counselling to family members and couples who are planning to be married. Realising the importance of differentiating the two