Evaluation of Red Cell Distribution Width (RDW) in Anemic Goats

Anemia in small ruminants causes severe economic losses to livestock farmers by poor weight gain, abortions and mortality in them. It was mainly caused by endoparasitic infestations with helminthic worms and ectoparasites like ticks and their associated infections.  The measurement of red blood cell distribution width (RDW) could provide a newer approach to the anemia (Souza et al., 2012).

Souza et al., (2017) reported RDW as a sensitive tool to assess erythrocyte sizes and variations and found more accurate than microscopic observations in detecting anisocytosis. It was also found more sensitive than MCV in assessing erythrocyte variations.

Extensive studies indicated Red Blood Cell Distribution width was used as a perdiction factor in various disease conditions in human medicine especially in cardiovascular disease (Patel et al., 2013), iron deficiency anemia (Piriyakhuntorn et al., 2018) and pulmonary hypertension (Yang et al., 2019). Further, few studies in Veterinary Medicine were also reported with special reference to canines anemias (Souza et al., 2017), pulmonary hypertension (Swann et al., 2014) and other illnesses (Martinez et al., 2019). The red blood cell distribution width (RDW) means measurement of degree of anisocytosis in the erythrocyte population and expressed as the coefficient of variation of the erythrocyte size distribution (Pastor et al., 1997; Hammarsten et al., 2010). The microscopic assessment of degree of anisocytosis has limitations and also found to be a time-consuming procedure which was later replaced by automated hematological analyzer providing immediate value along with estimations of all the hematological parameters.

Currently most of the veterinary institutes and private veterinary clinics were having modern automated hematological analyzers with species specific software to assess the hematology status and initiate effective therapeutic management in the ailing animals. There was limited data available on RDW in goats and was found particularly lacking in goat anemias. Hence the present study could provide the base line data for Red Blood Cell Distribution Width in goats.

The study was conducted at Veterinary Clinical Complex, Veterinary College and Research Institute, Orathanadu, Thanjavur, Tamil Nadu, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India. Latitude and longitude of the study area 10.6286°N, 79.2531°E. Instrument: Veterinary specific automated hematology analyzer (Vet Scan HM5, Germany) and the parameters selected for analysis were Hgb, HCT, RBCs, MCV, MCH, MCHC, RDW (RDWs and RDWC). The cases presented to the Veterinary diagnostic laboratory of Veterinary Clinical Complex, Veterinary College and Research Institute, Orathanadu, Thanjavur were selected for the study and the data was collected during the period 2015 to 2019.

Erythrocytes play an important role in the transport of oxygen during blood circulation. Alterations in RBCs volume and size would affect the organ and tissue perfusions. RDW was found more sensitive than MCV in assessing types of anemia and their prognosis (Neiger et al., 2002). Basing on the data available, cases with hemoglobin values lesser than and or equal to 8.0 g/dl and PCV less than and or equal to 22% were selected for the present study.

During the study a total of 264 blood samples collected from goats were processed in automated hematology analyzer. Out of which, 194 cases were found having hemoglobin and PCV values lesser than and or equal to 8.0 g/dl and 22%, respectively.

The RDW was used to describe the amount of variation in the size of red blood cells namely anisocytosis. RDW may be further reported as either standard deviation (RDWs) or coefficient of variation (RDWc), however RDWc was commonly employed. One standard deviation of RBC volume divided by the MCV times 100 i.e.
 

 
Red blood cells were found fairly uniform in size however an increase or decrease in variation i.e., anisocytosis could lead to changes in RDW.

Blood samples were collected from jugular vein in 2 ml capacity K3EDTA coated tubes and gently stirred for complete mixing of anticoagulant with blood and also just before analysis. The collected blood samples were processed in automated hematology analyzer (Vet Scan HM5, Germany) as per the instructions of manufacturer. Further the data of blood samples collected from anemic goats were compared with healthy (control) goats (n-7) maintained in the Livestock Farm Complex of Veterinary College and Research Institute, Orathanadu.

The effect of anemia between hematology indices was analyzed by t-test and expressed as Mean±Standard error (SE). Pearson’s correlation coefficient was used to test associations between variables. Results were considered significant at p<0.05 and highly significant at p<0.01 levels. Ethical statement: No ethical concern/permission was required for the present study.

In the present study, 194 goats were found suffering from anemia. The details of Mean, Standard error (SE) and t-test values of anemic (n-194) vs healthy goats (n-7) were presented in Table 1. On statistical analysis, Hemoglobin, Hematocrit, Mean corpuscular volume and Mean corpuscular hemoglobin were found highly significantly (p<0.01) decreased when compared to healthy goats.



According to Martinez et al., (2019) RDW was studied extensively in human patients whereas in dogs the quantitative measure of erythrocyte anisocytosis was limited. Further it augmented the diagnostic information in the anemic patients and also provided prognosis in varied disease conditions. In view of the relative scarcity of literature on RDW an effort has been made to study the variation of RDW in anemic goats.

The red blood cell distribution width (RDW) was considered as an index of the heterogeneity of circulating red blood cell size and conventionally referred to as anisocytosis and could be assessed by modern hematology analyzers (Lippi and Plebani, 2014; Salvagno et al., 2015).

RDW was found elevated under conditions of erythropoietic stress like iron, Vitamin B12 and folate deficiencies (Lippi and Plebani, 2014). Red blood cell damage caused by oxidative stress could lead to elevated RDW and decrease in lifespan of the erythrocytes (Semba et al., 2010). It could be suggested that supplementation of antioxidant nutrients may influence the RDW in anemic goats. Further an increase in RDW was also observed in regenerative anaemias because of increase in reticulocytes count rather than mature erythrocytes (Cavaliere, 2004). Zvorc et al., (2010) reported that RDW could be a useful indicator of the appearance of a younger population and increase in RDW occurs before the MCV exceeds the reference interval.

The details of the correlation between the variables i.e RDW indices (RDWs and RDWc) and Hb, HCT, MCV and RBCs in anemic goats (n=194) were presented in Table 2. The MCV was found positively correlated with RDWs and negatively correlated with RDWc. However, both RDWs and RDWc were found statically highly significant (p<0.01) with MCV. Hence, it may be construed that MCV strongly correlates with RDWs and RDWc. In the study, Hematocrit (HCT) was found negatively correlated with RDWs and RDWc, wherein RDWc was found statically highly significant (p<0.01) and RDWs significant (p<0.05). Similarly, Hemoglobin (Hb) was also found negatively correlated with RDWs and RDWc, wherein RDWs was found statically highly significant (p<0.01) and RDWc significant (p<0.05). In addition, RBCs was also found negatively correlated with RDWs and RDWc, wherein RDWs was found statically highly significant (p<0.01) and RDWc as non-significant.



Guglielmini et al., (2021) reported increase in RDW was significantly associated with a negative outcome in dogs with myxomatous mitral valve disease (MMVD), with or without concurrent infections, on treatment, independently from anaemia and or concomitant changes in MCV.

RBC indices in dogs indicate the bone marrow responses in anemia. The indices, such as mean corpuscular volume and red blood cell distribution width, could provide valuable information in establishing diagnosis in anemic patients. These laboratory parameters were frequently overlooked in veterinary clinical practice (Zvorc et al., 2010).

Severe anemia could cause obvious heterogeneity of the RBCs size and an increase in RDW level. Anemia was recognized as a well-documented risk factor in congestive heart failure (CHF), the potential mechanisms of which include inflammatory stress, inadequate production of erythropoietin and the impact of comorbidities (Forhecz et al., 2009). Elevations in RDW due to alterations in the osmolality of the circulating blood decreases the ability of red blood cells and undergo deformation under certain patho-physiological conditions resulting in low microvascular perfusion and later organ dysfunction. In this study Red blood cell distribution width (RDW) was recorded and compared among healthy and anemic goats. Erythrocytes play an important role in the transport of oxygen during blood circulation. Alteration of RBCs in volume and size would affect organ and tissue perfusions. RDW was found more sensitive than MCV in assessing the types of anemia and their prognosis (Neiger et al., 2002). The estimation of RDW plays a pivotal role not only in anemia and but also in other organ disorders. The baseline RDW may have clinical significance for assessing clinical outcome and severity of various pathological conditions. A myriad of factors has an impact on red blood cell population dynamics which include production, maturation and turnover. A delay in the red blood cell clearance in pathological conditions might represent one of the leading determinants of increased anisocytosis.

Elevated red cell distribution width was recorded in anemic goats. Further studies on RDW could reveal new insights into inflammation mechanisms, disease diagnosis and their prognosis in goats.

The Authors are grateful to the Director of Clinics TANUVAS and the Dean VCRI Orathanadu for all the facilities provided for carrying out this study.  

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