Distribution of haematological indices among subjects with Blastocystis hominis infection compared to controls

Introduction

Blastocystis hominis (B. hominis) is an obligate anaerobic protozoan found in the human large intestine and is the most common eukaryotic organism reported in human faecal samples [1]. The parasite is a zoonotic organism, found in birds and swine, and can be transmitted easily to humans via the oral-faecal route. The prevalence of B. hominis varies in different countries from 1.5% to 50% [2]. At first it was thought that the organism is a non-pathogenic yeast, but later B. hominis was classified as a protozoan of the stramenopiles line [3]. The pathogenesity of B. hominis is still in debate because this parasite is very common in the healthy population without causing any symptoms [4, 5]. However, some studies suggest that it is a potentially pathogenic protozoa and it was reported that B. hominis causes various problems such as watery diarrhoea, abdominal pain, bloating, fever, nausea and gastrointestinal problems [5, 6]. In addition, it was reported that B. hominis may contribute in colitis, terminal ileitis and rectal bleeding [7, 8]. Blastocystis hominis contributed to anaemia in children aged 8–10 years old as per one study [9].

Aim

The aim of the study was to compare haematological indices in cases with Blastocystis hominis infection with healthy controls.

Material and methods

From 2001 to 2012, 97,600 stool examinations were done in 4 university hospitals. Parasites were observed in 46200 specimens. Of these cases, subjects with complete laboratory investigation (complete blood count – CBC, ferritin, total iron binding capacity – TIBC, and serum) were included in this study as the case. Of these cases, 6851 cases had only B. hominis infection. This retrospective study was carried out on 10786 subjects who visited the hospital for routine checkup. In this study, subjects who attended for routine checkup were included. Of 8761 cases with B. hominis infection, 6851 cases with complete laboratory examination were included. In this case control study, 6851 cases with B. hominis infection and 3615 controls were included. Age, haemoglobin (Hb), serum iron, TIBC, white blood cell count (WBC), red cell distribution width (RDW), platelet (PLT), mean corpuscular volume (MCV), haematocrit (HCT) and erythrocyte sedimentation rate (ESR) were recorded for cases and controls.



Statistical analysis



SPSS software version 13.0 (Chicago, IL, USA) was used for analysis. Independent sample t-test and 2 tests were used for comparison. A value of p < 0.05 was considered significant.

Results

Demographic features are shown in Table I. There were significant differences between the two groups regarding distribution of iron levels, with the exception of iron level range 120–140 g/dl (Table I). For iron level < 80 g/dl, the relative frequency was significantly higher in the case group. For iron level > 120 g/dl, the relative frequency was significantly higher in the control group (p < 0.05).

Frequency of TIBC = 300–350 g/dl and 400–450 g/dl was higher among the cases, and the frequency of TIBC = 350–400 g/dl was significantly higher among the controls (Table II). There was a significant difference between the two groups regarding platelet count, with the exception of PLT < 150,000/l and PLT > 450,000/l (Table II). Subjects with an eosinophil count of 1% were significantly more frequently in the case group than in the control group. The reverse was true for subjects with an eosinophil count of 2%. There was no significant difference between the two groups in eosinophil count in other ranges (Table II).

Discussion

Occult blood was more common in the group with B. hominis infection compared to the control group. This may be due to colitis from the B. hominis infection. Leder et al. studied over 2800 healthy people over 15 months [10]. They did not find significant correlation between clinical symptoms and the presence of B. hominis. In the study by Zuckerman et al., colonsocopy did not show any significant abnormality [11]. In the study by Wakid on 1238 workers in the western region of Saudi Arabia, no significant correlation was found between blastocystis infection and occult blood [12]. Our samples were collected from hospitals. These differences may be due to selection bias.

In our study the frequency of iron level < 80 was significantly higher in subjects with B. hominis infection. In the study by El Deeb et al. on pregnant woman with iron deficiency anaemia compared to those without iron deficiency, the frequency of B. hominis was significantly higher in the first group [13]. In another study by Yavasoglu et al., the rate of B. hominis infection was significantly higher among cases with iron deficiency anaemia [14]. In the study by Cheng et al. haemoglobin, neutrophil count and haematocrit were decreased in subjects with B. hominis infection [15]. In the recent study by El Deeb and Khodeer, the frequency of parasites was significantly higher in cases with iron deficiency (anaemia) compared to non-anaemic patients [16].

Although the exact mechanism of iron deficiency in subjects with B. hominis was not understood, some studies showed invasion of B. hominis in the gastrointestinal tract and subsequent blood loss [8]. In the literature, B. hominis was reported as the possible cause of acute abdomen in children [17]. There is evidence regarding the presence of inflammation when B. hominis is present [18]. Yavasoglu et al. did not find evidence that supported the invasion of mucosa [14].

Another mechanism that may lead to the development of anaemia in blastocystis is that infected subjects may return to the molecular structure of B. hominis. Stenzel et al. showed that in the endocytic pathway of B. hominis cationic ferritin is essential [19].

Although there have been several published studies regarding B. hominis infection, there are few publications on its association with haematological indices.

Limitations – the method of this study was retrospective, and this is the main limitation.

Conclusions

Blastocystis hominis is a possible factor in haematological abnormalities. Another cohort study on a healthy population is recommended for determination of the cause and effect relationship.

Acknowledgments

This study was supported by financial support from Student Research Committee of Ahvaz Jundishapur University of Medical Sciences (NO: 91S.83).

References

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Received: 11.03.2013

Accepted: 29.12.2013