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KMID : 0384119860060020437
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Korean Journal of Clinical Pathology
1986 Volume.6 No. 2 p.437 ~ p.447
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Studies on Clinical Application of Enzyme-linked Immunosorbent Assay (ELISA) for the Diagnosis of Typhoid Fever
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Abstract
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Laboratory diagnosis of typhoid fever is essential for the proper management of the patient because this disease is still prev?is it., in Korea. Widal test has been widely used for the diagnosis of this disease but its sensitivity and specificity are disappointing. Furthermore bacteriological culture rate is also relatively low possibly due to the indiscriminate use of antibiotics.
Enzyme-linked immunosorbent assay (ELISA) is an useful tool for the detection of very small amount of antibody. Therefore, this method has been tried for the serodiangosis of typhoid fever. The author reevaluated this method using lipopolysaccharide(LPS) of Salmonella typhi as the antigen in twenty-five cases of bacteriologically proven typhoid fever, 14 cases of clinically diagnosed typhoid fever, 4 cases of paratyphoid fever, 48 cases of nontyphoidal diseases and 45 cases of healthy control subjects.
The ELISA for anti-LPS antibody of IgM and IgG classes was performed using alkaline phosphatase conjugated anti-human globulin. It was found that the optimum coating concentration of LPS antigen was 25,ag/ml and the optimum serum dilution was 1 : 40. The sensitivity of ELISA for IgM and IgG were 60% and 9201o, respectively. The specificity of IgM and IgG were 89.6% and 77.9%, respectively. Among the 11 cases of false positive IgG,4 were tuberculosis patients and 3 were cancer patients. Rheumatoid factor positive patients showed significantly high IgM level compared to the nontyphoidal disease group. Four cases of
paratyphoid fever patients showed increased IgG and whose absorbance values were not significantly different from those of typhoid fever group. It was found that in the cases either whose IgG absorbance value is above 1. 0 or both IgM and IgG absorbances were positive, the diagnostic sensitivity of typhoid or paratyphoid
fever becomes 75.6%, specificity 95. g%, positive predictive value 91.7 j and
negative predictive value 86.%.
Based on these results, it is certain that the ELISA method using S. typhi LPS is highly sensitive and specific for the detection of both IgM and IgG antibodies, and one could conclude that this method is an useful serodiagnostic tool for the diagnosis of typhoid fever.
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KEYWORD
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