Anisha Elizabeth Jacob1, Marina Thomas2, Boppe Appalaraju3
BACKGROUND
Scrub typhus is a febrile disease, the clinical diagnosis of which is difficult due to
its vague symptoms. Scrub typhus is diagnosed mainly via serological tests.
Sensitivity of Weil Felix was found to be poor, but the specificity of Weil Felix was
variable in different studies. Enzyme linked immunosorbent assay (ELISA) IgM is
known to be a sensitive test, but its specificity was variable in different studies.
Therefore, in this study we have compared these two tests with the gold standard
IFA.
METHODS
The study was performed as a cross-sectional study. Among the suspected scrub
typhus cases, fifty consecutive IFA scrub typhus positive and fifty consecutive IFA
negative samples were taken for comparison of Weil Felix and ELISA tests. The
indirect fluorescent antibody test (IFA) was taken as the gold standard.
RESULTS
The sensitivity of ELISA and Weil Felix at a titre of 1 : 160 was found to be 96 %
and 40 % respectively. The specificity of ELISA and Weil Felix at 1 : 160 and was
found to be 88 % and 94 % respectively.
CONCLUSIONS
Scrub typhus should be kept in mind as a possible diagnosis in acute febrile
illnesses. Weil - Felix was found to have a good specificity but low sensitivity.
Hence, if the results by Weil Felix are negative, scrub typhus cannot be ruled out
and may require further testing. ELISA showed good sensitivity making it a
preferable screening test but is not highly specific and confirmation with IFA may
be required when feasible.
