A DIAGNOSTIC BLOOD TEST FOR SCABIES
Gamal A. Abo-Sheishaa, Tarek KH. Zaalouk , Mostafa El Shahat Mostafa and Zakaria Mahran*
Parasitology and Dermatology* Departments, Faculty of Medicine, Al-Azhar University
Background: Ordinary scabies is very difficult to diagnose. Parasitological techniques are rather insensitive and clinically scabies can mimic other skin diseases such as eczema, psoriasis, and atopic dermatitis. A presumptive diagnosis of scabies requires confirmation by recovering mites, mite fecal pellets, and eggs from the corneal layer of the epidermis. A sensitive and specific blood test to detect scabies-specific circulating antibodies would allow a physician to quickly make a correct diagnosis. One of the problems with developing such a test is that many of the antigens from scabies mites cross-react with antigens from house dust mites. Aim of the work: The present study was designed to identify Sarcoptes scabiei -specific antibodies present in the sera of patients with ordinary scabies and examine possible cross reaction. Subjects and methods: The study was held out at Dermatology Clinic and Parasitology Department (Al-Azhar Faculty of Medicine) from December 2015 to May 2016. It included 30 patients with ordinary scabies. In addition, 30 healthy, age and sex-matched individuals were included as a control group. Skin prick test was done for house dust mites, pollens and grass. Serum was obtained for inclusion in determination of different Igs (IgE, IgM, and IgG) specific for house dust mite and scabies. Results: Skin prick test showed significant increase of positive cases for HDM (Dp) and HDM (Df) and each of IgG, IgM and IgE specific for scabies showed significant increase in study group. However, there was no significant difference between study and control groups as regard to IgG, IgM and IgE specific for both subtypes of HDM. IgG in study group was positive for scabies in 40.0%, for HDM (Dp) in 33.3% and for HDM (Df) in 36.7%. The difference between each of subtypes of HDM and scabies was statistically non-significant. IgM was positive for scabies in 50.0% of patients, for only 13.3% and 16.7% for HDM (Dp and Df) respectively. The difference between scabies and each of two subtypes of HDM was statistically significant. The situation for IgE was similar to that of IgG. Conclusion: There was cross-reactivity between Sarcoptes scabiei and house dust mites as evidenced by skin prick test and serological tests. Detection of IgM specific for Sarcoptes scabiei in early phase. Thus can be used as an early diagnostic test.