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BRIEF COMMUNICATION  
Year : 2011  |  Volume : 54  |  Issue : 1  |  Page : 121-123
Use of "Parasep filter fecal concentrator tubes" for the detection of intestinal parasites in stool samples under routine conditions


1 Department of Pathology Microbiology, Aga Khan University, Karachi - 74800, Pakistan
2 Department of Pathology Microbiology, Medical College, Aga Khan University, Karachi, Pakistan

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Date of Web Publication7-Mar-2011
 

   Abstract 

Parasitic gastrointestinal infections are a major cause of morbidity and mortality in the developing world, with stool microscopy being the mainstay of diagnostic practice. Both direct microscopy and concentration techniques can be utilized; direct microscopy may be time consuming and tedious; however clinical laboratories in developing countries lack trained staff who can effectively use concentration methods. In our practice we used the Parasep O and P filter concentrator tubes (manufactured by DiaSys Ltd, Berkshire, England. Product Code 146000) along with direct microscopic techniques and found that Parasep filters enhanced the ability to detect intestinal parasites that would have been missed on routine microscopy. We found the Parasep filter concentration method to be easy, cost-effective and reliable for routine stool examinations.

Keywords: Closed tube fecal concentration system, intestinal parasite detection, Parasep fecal filter

How to cite this article:
Zeeshan M, Zafar A, Saeed Z, Irfan S, Sobani ZA, Shakoor S, Beg MA. Use of "Parasep filter fecal concentrator tubes" for the detection of intestinal parasites in stool samples under routine conditions. Indian J Pathol Microbiol 2011;54:121-3

How to cite this URL:
Zeeshan M, Zafar A, Saeed Z, Irfan S, Sobani ZA, Shakoor S, Beg MA. Use of "Parasep filter fecal concentrator tubes" for the detection of intestinal parasites in stool samples under routine conditions. Indian J Pathol Microbiol [serial online] 2011 [cited 2019 Jun 26];54:121-3. Available from: http://www.ijpmonline.org/text.asp?2011/54/1/121/77358



   Introduction Top


Enteric parasitic infections are a major disease burden worldwide, constituting a significant proportion of all intestinal problems. [1],[2] They pose a greater threat to developing countries owing to the lower standard of hygiene, poor sanitary habits, and health seeking behavior. [3] The spectrum of clinical presentation is wide; from asymptomatic carrier states to severe diarrhea, abdominal pain, and malnutrition leading to severe anemia. Light microscopy examination is considered the main stay for confirmation of clinical diagnosis, [4],[5] with demonstration of the cyst or trophozoite stage in fecal sample essential for the recognition of parasite. [6] However, the probability of a positive result via direct microscopy is very poor due to the low density of parasites in the specimens obtained; in order to improve the parasitic yield concentration methods are employed. Fecal concentration methods encompass conventional open methods like the Ridley-Allen method, which is labor intensive and has been associated with inherent health and safety hazards, and the recently improved closed systems. [7] The closed concentration system allows rapid, reliable, and safe detection of intestinal parasites by inexperienced technologists.

The Parasep filter concentrator tube is a newer modification of the closed concentration system, which can easily be adopted in any routine microbiology laboratory. Here we describe our experience with the aforementioned system in comparison to direct microscopy in diagnosing intestinal parasitic infections.


   Methods and Results Top


Semi-solid and watery diarrheal specimens submitted for routine examination in the clinical microbiology laboratory of our hospital during May 2008 to July 2008 were included in this prospective study. Of all submitted samples, 125 specimens were randomly selected for inclusion in the study and were initially studied without concentration by two experienced technologists and results were recorded. The samples were then concentrated using the Parasep concentrator tube (manufactured by DiaSys Ltd, Berkshire, England. Product Code 146000), according to the manufacturer's instructions [Figure 1], and microscopic examination was repeated with the sediments of each centrifuged specimen by preparing two 22 × 22 mm cover slip preparations (one with saline and one with iodine).
Figure 1: Use of Parasep fecal filter in the laboratory. (a) Sealing of the Parasep by screwing in the sedimentation cone; (b) fecal sample in Parasep---this will be followed by vortexing and (c) centrifugation after inverting; (d) sedimentation cone after centrifugation, followed by (e) preparation of slide from sediment for microscopic examination.

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We have demonstrated that the Parasep concentration test is useful in the laboratory in terms of (1) increase in the yield of parasites as compared to direct microscopy; (2) processing time and test turnaround time compared to conventional concentration techniques; and (3) cost.

Increase in Yield


Of 125 samples that were tested by the two methods, 100 samples were negative for parasites on direct microscopy; 13 of these samples were positive when examined after processing in the Parasep system [Table 1]. Furthermore, in the 25 samples that were initially positive on direct microscopy the concentration of parasites was higher using the Parasep system.
Table 1: Parasites detected by the concentration system only

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Processing Time and Test Turnaround Time

Both the Parasep method and conventional formal-ether sedimentation methods were conducted on the 25 samples negative by direct microscopy and processing times were recorded by an independent observer. Mean time for processing using the Parasep system was considerably lower at 6 min/sample when compared to the conventional formal-ether sedimentation method at 12 min/sample.

Cost

Cost per test was calculated for conventional stool concentration by formal-ether method, and for the Parasep test; with conventional formal-ether methods costing less than the Parasep method at USD 0.30/sample versus USD 0.9/sample. However the increased processing time and the requirement of trained personnel of the conventional method have not been accounted for in this analysis. It is our assumption that the limitations of the conventional method if factored into the calculation will result in comparable if not lower costs of the Parasep method.

However, the cost difference is phenomenal when costs incurred per patient are considered especially since parasitism is more common in lower socio-economic strata. We propose therefore that manufacturer-led initiatives for decreasing test costs in developing countries be advocated.


   Discussion Top


Fecal concentration tubes have been in use for the last 30 years, [8] over this period of time various modifications have been made to the system improving the yield of eggs, cysts, and trophozoites of different parasites of variable sizes and shapes. The overall effectiveness of closed fecal concentration tubes has been satisfactory for different intestinal parasites; [7] however the sensitivity is lower in cases of low intensity infections when compared to conventional concentration methods. [9] Parasep O and P filter fecal concentrator tubes are a modification in the system with a small size sieve (425 μm) used to trap rejected particles and debris in stool samples, preventing their extrusion into the sedimentation cone during centrifugation. Thus improving the clarity results in an increased accuracy of diagnosis during microscopy. [10] In other concentrator tubes, the size of the filter pores may vary between 600 μm and 2000 μm thereby resulting in the possibility of missing small parasitic forms such as cysts of Entamoeba and G. lamblia along with the presence of debris in background material of the final slide prepared.

Using this system we were able to detect cysts of different parasites and helminth eggs; however no coccidian oocysts or microsporidian spores were identified. This may be attributable to their small size and mass, whereby they may become entrapped in the ether or ethyl acetate plug and fail to sediment properly. Surfactants such as Triton® X-100 have also been recommended on the basis that the surfactant helps in reducing the surface tension in mucus and fecal lumps enhancing filtration and freeing additional helminth eggs that may otherwise remain entrapped in the specimen. However the manufacturers of the Parasep concentration tube do not recommend the use of surfactants and in our opinion the use of surfactants would be superfluous with an added expenditure as they have already demonstrated a reliable increase in the number of detected parasites and positive tests. A separate trial is however warranted to establish the role of surfactants.

The decreased processing time required may increase the output and processing capabilities of various laboratories. Therefore in routine clinical laboratories with limited resources especially in developing nations these tubes may offer an alternative for direct microscopy and conventional concentration techniques by providing a hazard-free, reliable and safe method with satisfactory efficacy at improving the parasitic yield in fecal specimens. However, the cost-effectiveness needs improvement by implementing manufacturer-based cost-lowering initiatives.

 
   References Top

1.Kucik CJ, Martin GL, Sortor BV. Common intestinal parasites. Am Fam Physician 2004;69:1161-8.  Back to cited text no. 1
[PUBMED]    
2.Harp JA. Parasitic infections of the gastrointestinal tract. Curr Opin Gastroenterol 2003; 19:31-6.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Fernandez MC, Verghese S, Bhuvaneswari R, Elizabeth SJ, Mathew T, Anitha A, et al. A comparative study of the intestinal parasites prevalent among children living in rural and urban settings in and around Chennai. J Commun Dis 2002;34:35-9.  Back to cited text no. 3
[PUBMED]    
4.Procedures for the Recovery and Identification of Parasites from the Intestinal Tract, Approved Guideline, M28-2A. Clinical and Laboratory Standards Institute, Villanova, PA. Clinical and Laboratory Standards Institute., 2005.  Back to cited text no. 4
    
5.Garcia LS, SJ, Fritsche TR. Selection and use of laboratory procedure for diagnosis of parasitic infection of gastrointestinal tract Washington DC .ASM press 2003.  Back to cited text no. 5
    
6.Cook GC.Entamoeba histolytica and Giardia lamblia infections: current diagnostic strategies. Parasite 1995;2:107-12.  Back to cited text no. 6
[PUBMED]    
7.Perry JL, Mathews JS, MillerGR. Parasite Detection Efficiencies of Five Stool Concentration Systems.J Clin Microbiol;1990;28:1094-7.  Back to cited text no. 7
    
8.Zierdt WS. A simple device for concentration of parasite eggs, larvae, and protozoa. Am J Clin Pathol1978;70:89-93.  Back to cited text no. 8
[PUBMED]    
9.Lier T, Simonsen GS, Wang T, Lu D, Haukland HH, Vennervald BJ, Johansen MV. Low sensitivity of the Formol-Ethyl Acetate sedimentation concentration technique in low-Intensity Schistosoma japonicum infections. PLoS Negl Trop Dis 2009;3:e386.  Back to cited text no. 9
[PUBMED]  [FULLTEXT]  
10.Garcia LS. Practical Guide to Diagnostic Parasitology. 2nd ed. ASM Press, Washington, D.C., 2009.  Back to cited text no. 10
    

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Correspondence Address:
Mohammad Asim Beg
Department of Pathology and Microbiology, The Aga Khan University, P.O. Box 3500, Karachi - 74800
Pakistan
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Source of Support: Department of Pathology and Microbiology, Aga Khan University, Karachi, Pakistan, Conflict of Interest: None


DOI: 10.4103/0377-4929.77358

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