Introduction

The use in veterinary medicine, automated instruments, laboratory tests for blood has increased in recent years and there are few studies about the benefits that new haematological parameters determined by such devices offer, one of those parameters, which is widely used in human medicine for classification of anemias, is the extent of erythrocyte distribution (RDW) that determines the rate of anisocitose in the blood, besides offering a histogram Erythrocytic (Bessman et al 1983). The index most commonly used to assess the degree of anisocytosis is the mean corpuscular volume (MCV), which is typically calculated using date from volume and globular erythrocyte counts. However, many changes in the volume of these cells are not detected by examining only the MCV. A large percentage of cells with modified volume are required to produce a MCV abnormal red blood morphology, and evaluation to determine the presence of anisocytosis method is limited because of its subjectivity (Roberts & El Badawi 1995). This study was realized to determine RDW in dogs from northern region of Brazil. This is the first research using this kind of analysis in this Brazilian region.

Table 1. Reference interval values, means and standard deviation for the parameters RBC, RDW, MCV of blood samples from cats collected during the month of November of 2008 in the region of Belém--Para State, Brazil. 2009.

RBC = (Red Blood Count 106/µL)
RDW = (Red Cell Distribution Width %)
MCV = (Mean Corpuscular Volume fL)
Reference interval (CV=95%)

Materials and Methods

This study was conducted in November 2008, in the city of Belém, Pará State, Brazil. The prevailing climate in this region is equatorial, with constant rain and directly influenced by the Amazon rain forest. 32 cats (13 females and 19 males) of various breeds were studied, ages ranging from twelve months to 5 years, from private breeders. After clinical examination, healthy animals were separated and identified and a blood sample was taken from jugular vein. Processing and analysis were done in Hematological Laboratory of Clinical Pathology "Amaral Costa", at Belém, Pará state, Brazil. All samples were processed at the same day of collection, following the techniques routinely used in that laboratory (standard operating procedure), using Analysis Hematological Cell-Dyn 3700 unit (ABX Diagnostic, Montpellier, France) showing a good performance and testing quality control during the daily analyses. RBC (Red Blood Cell Count), MCV (Mean Corpuscular Volume) and RDW (Red cell distribution Width) were evaluated. Results were compared between females and males (group 1 and 2) for the same variables using the analysis of variance by ONE WAY ANOVA statistical program--Bioestat. The averages were then compared by Tukey test at 5% probability. The different cellular parameters were also submitted to testing to verify a correlation of the presence of any linear association between the data.

Results

There was no statistical difference between females and males. The reference interval values (CI 95%), the mean and standard deviations are described in Table 1. The values of the Pearson correlation for RBC and RDW were positive (R2 = 0.3809) and significant (p < 0002) to RDW and MCV was also significant (p < 0001) but negative (R2 = 0.3903).

Discussion and Conclusions

The average parameter RDW found in this research is within the range of reference 14 to 31% and from 17.3 to 22% cited in the respective Petcenter (2008) and The University of Guelph (2008). Statistical analysis showed no significant differences between males and females, with corroborating Flaiban & Balarin (2004), in their studies with dogs, where the values of RDW were correlated to the packed cell volume (PCV) and the animals were divided into four classes, and the average values of the RDW Classe1 (VG: < 25%), Class 2 (VG 25-35%), class 3 (35 45%) and Class 4 ( > 45%), respectively: 14.10%, 12.80%, 12.44% and 12.02%. Although the values found in this work are mostly within the literature cited in other studies in different regions should be made because the literature describes a wide variation in the values of RDW. Blood disorders are the main responsible for this enormous change in values. Perret et al., (2001) described in dogs with regenerative anemia, is greater or equal to 10, 9 to RDW in 46% of animals and this percentage was 66% of dogs that had a strong reticulosis. So RDW is a parameter that is part of a set of data, and should not be interpreted in isolation, is very important as a tool for the differential diagnosis of anemia and other systemic diseases. Depending on the scarce literature on RDW found in domestic cats, the values of this study can be used as parameters for males and females in the region until further studies can be conducted.

References

1.  Bessman D, Gilmer JR PR, Gardner FH. Improved classification of anemias by MCV and RDW. American Journal of Clinical Pathology, Philadelphia, v.322, p.322-326, 1983.

2.  Roberts GT, El Badawi SB. 1995. Red cell distribution width index in some hematologic diseases. American Journal Clinical Pathology. 83: 226-236.

3.  The Pet Center.Com. 2009. The internet animal hospital. Disponível em: http://www.thepetcenter.com/home.aspx. Acesso em janeiro de 2009.

4.  The internet University of Guelph. 2009. Disponível em: http://www.uoguelph.ca. Acesso em janeiro de 2009.

5.  Flaiban KKMC, Balarin MRS. 2004. Estudo comparativo entre a amplitude de variação dos eritrócitos (RDW--Red Blood Cell Distribution Width) e o Volume Globular (VG), Volume Globular Médio (VGM) e a presença de anisocytosis em extensão sanguínea em cães. Semina: Ciências Agrárias. Londrina. 2. 25:125-130

6.  Perret D, Trumel C, Diquélou A, Dossin et O, Guelfi JF, Espie C. 2001. Service de Médecine des carnivores domestiques. Laboratoire d'hématologie. Revue Méd. Vét. 7. 152: 549-554.