Comparative Evaluation of ENTEROSCREEN-WB and Widal test in Suspected Cases of Enteric Fever

Enteric fever is a major public health problem in developing countries like India. An early and accurate diagnosis is necessary for a prompt and effective treatment. We have evaluated the diagnostic accuracy of ENTEROSCREEN-WB as compared to Widal test in rapid and early diagnosis of enteric fever. A total of 145 patients serum samples were tested by Rapid ENTEROSCREEN-WB and Widal test including clinically suspected cases of enteric fever of all age groups. Vaccinated individuals, patients on antibiotic therapy, patients who have other associated conditions, patients suffering from fever due to non-enteric etiology & non consent patients were excluded. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of ENTEROSCREEN-WB considering Widal test as gold standard were 50% and 96%, 66.66% and 92.30% respectively. ENTEROSCREEN-WB was found to be significantly more specific. Although the Rapid ENTEROSCREEN-WB tests are meant to diagnose of S. typhi. Ten patients who were ENTEROSCREEN-WB positive for S. typhi were also positive by Widal test. Key wordsEnteric fever, Rapid ENTEROSCREEN-WB, Non-enteric etiology, S. typhi, Widal test -------------------------------------------------IJLSSR----------------------------------------------INTRODUCTION Typhoid fever is an acute, generalized infection of the reticuloendothelial system, intestinal lymphoid tissues and gallbladder caused by Salmonella typhi. The annual incidence of typhoid fever has been reported as more than 13 million cases in Asia. Typhoid fever is endemic and one of the commonest infectious diseases prevalent in India. India is the second most populous country of the world with majority inhabiting the rural areas with little access to modern diagnostic tools . The isolation of the organism from blood, bone marrow or stool is required to confirm the diagnosis, which is time consuming. Blood culture is regarded as the gold standard for diagnosis & carry 70-75% diagnostic yield in the first week of illness. In WIDAL-test the agglutination titer will depend on the stage of disease. Received: 06 October 2015/Revised: 16 October 2015/Accepted: 28 October 2015 Agglutinins will usually appear by the end of the 1st week, so that blood taken earlier may give a negative result. The titer increases steadily until the third or the 4th week, after which it declines gradually. ENTEROSCREEN-WB is a rapid dot-enzyme immune assay (EIA), which detects IgG and IgM antibodies to a specific outer membrane protein (OMP) antigen of Salmonella enteric serotype Typhi. Typhi dot becomes positive as early as in the first week of fever; the results can be visually interpreted and is available within one hour. MATERIALS AND METHOD A. SPECIMENS Blood for culture must be taken repeatedly. In enteric fevers and septicemias, blood cultures are often positive in the first week of the disease. Bone marrow cultures may be useful. Urine cultures may be positive after the second week. B. BACTERIOLOGIC METHODS FOR ISOLATION OF SALMONELLAE 1. Differential Medium Cultures—MacConkey’s or Deoxycholate medium permits rapid detection of lactose non-fermenters. Bismuth sulfite medium permits rapid detection of salmonellae which form black colonies because of H2S production. Many salmonellae produce H2S. 2. Selective Medium Cultures—The specimen is plated on salmoCorrespondence details *Shabnam Parveen Department of Microbiology Integral Institute of Medical Sciences and Research, Lucknow, India Mail [email protected] Research Article (Open access) International Journal of Life-Sciences Scientific Research (IJLSSR), VOLUME 1, ISSUE 2 http://ijlssr.com IJLSSR © 2015 All rights are reserved nella-shigella (SS) agar, Hektoen enteric agar, XLD, or DeoxycholateCitrate agar, which favor growth of salmonellae and shigellae over other Enterobacteriaceae. 3. Enrichment Cultures— the specimen (usually stool) also is put into selenite F or tetrathionate broth. After incubation for 1–2 days, this is plated on differential and selective media. 4. Final Identification— suspected colonies from solid media are identified by biochemical reaction patterns and slide agglutination tests with specific sera. C. SEROLOGIC METHODS 1. Tube Dilution Agglutination (Widal Test)The Widal test, which detects agglutinating antibodies to lipopolysaccharide (LPS) (TO) and flagella (TH), was introduced over a century ago and is widely used for the serological diagnosis of typhoid fever. In the original format, the Widal test required acute and convalescent phase serum samples taken approximately 10 days apart. Most recently, the test has been adapted for use with a single, acute phase serum sample. This is a test for the measurement of H and O agglutinins for typhoid and paratyphoid bacilli in the patient’s sera. Equal volumes of serial dilutions of the serum and O, H, AH, BH antigens were mixed in the test tubes and incubated in a water bath at 37C overnight. 2. Rapid Diagnostic Test (ENTEROSCREEN-WB device): ENTEROSCREEN-WB utilizes the principle of immunochromatography, a unique two-site immunoassay on a nitrocellulose membrane. ENTEROSCREEN-WB is a dual test device assembly comprising of an IgM detection test assembly and an IgG detection test assembly. The conjugate pad of the IgM test assembly consists of two components, the Anti-human IgM antibody conjugated to colloidal gold and rabbit globulin conjugated to colloidal gold. Similarly the IgG test assembly consists of Anti-human IgG antibody conjugated to colloidal gold and rabbit globulin conjugated to colloidal gold.