INVESTIGATION OF Strongyloides stercoralis INFECTION AMONG CANCER PATIENTS AT HOSPITAL UNIVERSITI SAINS MALAYSIA USING MOLECULAR, SEROLOGICAL AND PARASITOLOGICAL TECHNIQUES
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Date
2012
Authors
ABDELRAHMAN, MOHAMMAD ZUETER
Journal Title
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Publisher
Pusat Pengajian Sains Perubatan Universiti Sains Malaysia
Abstract
Strongyloidiasis is thought to be one of the most commonly neglected parasitic infections globally, especially in the tropics and sub-tropics. However, public health significance of the disease is far from being negligible since the infection can remain dormant for decades in the host and may be activated after immunity dysregulation caused by immunosuppressants administration, such those given in patients with cancer and autoimmune diseases. The laboratory diagnosis of S. stercoralis is known to be problematic; the sensitivity and specificity of immunodiagnostic assays can vary considerably and the number of larvae in stool sample can be very low. In this study, 192 blinded samples of stool and serum from cancer patients at Hospital Universiti Sains Malaysia (HUSM) were tested by direct microscopy, ELISAs and real time PCR to determine the prevalence of S. stercoralis infection. The results would help the clinicians at USM to decide whether the detection of S. stercoralis is needed for the cancer patients at HUSM before starting chemotherapy.
A total of 192 patients were evaluated from December, 2010 to August, 2011. About 35% of patients were immunosuppressed at the time of sampling. Stool samples were investigated for S. stercoralis larvae by direct microscopic examination. Real-time PCR using specific S. stercoralis primers and probes was performed on extracted DNA from stool samples. Serological diagnosis was performed using indirect enzyme-linked immunosorbent assay (ELISA) for specificdetection of IgG, IgE, and IgG4 antibodies. ELISAs were also performed on control samples that comprised 25 serum samples from healthy individuals and 24 serum samples positive for otherparasitic infections. In addition, real-time PCR was performed on 53 stool samples positive for infections other than strongyloidiasis. Of the 192 samples examined, 1(0.5%) was positive for S. stercoralis by direct microscopy, 3(1.6%) by real-time PCR, 8(4.2%) by lab-based IgG ELISA, 3(1.6%) by commercial IgG ELISA and 6(3.1%) by lab-based IgG4 ELISA. Serum IgE was negative in all samples. Among
the eleven positive cases, real-time PCR, microscopy, commercial IgG-ELISA, and lab-based ELISAs for IgG, IgG4 and IgE were positive for 3(27.2%), 1(9.0%), 3(27.2%), 8(72.7%) , 6(54.5%), and 0(0%), respectively
This study showed that the lab-based ELISA for detection of serum IgG was a good and cost effective screening tool for active and chronic strongyloidiasis, since six of eight cases positive for lab-based IgG were also positive with other tests. In addition, lab-based IgG4-ELISA performed well in comparison with lab-based IgG-ELISA and real-time PCR; therefore it can also be used as screening tool for strongyloidiasis. In conclusion, this study has shown the importance of diagnosis of strongyloidiasis among cancer patients at HUSM. Real-time PCR, lab-based IgG ELISA and IgG4-ELISA assays used in this study were able to detect the infection in these patients. The results showed that a combination of serum IgG and IgG4 are the best serological tests for screening of strongyloidiasis in cancer patients before and in between chemotherapy courses. Positive results may be tested by repeated stool microscopy and real-time PCR. Appropriate treatment can then be administrated and a follow-up screening for IgG and IgG4 can be performed.
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Keywords
PARASITOLOGICAL TECHNIQUES