| ORIGINAL ARTICLE |
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| Year : 2011 | Volume
: 29
| Issue : 1 | Page : 47-50 |
Nested polymerase chain reaction on blood clots for gene encoding 56 kDa antigen and serology for the diagnosis of scrub typhus
JAJ Prakash1, ML Kavitha2, E Mathai1
1 Department of Microbiology, Christian Medical College, Vellore - 632 004, India
2 Department of Haematology, Christian Medical College, Vellore - 632 004, India
Correspondence Address:
JAJ Prakash
Department of Microbiology, Christian Medical College, Vellore - 632 004
India
 Source of Support: Institutional review board, Christian Medical College, Vellore, India, Conflict of Interest: None  | Check |
DOI: 10.4103/0255-0857.76524
Purpose : Scrub typhus is a zoonotic illness endemic in the Asia-Pacific region. Early diagnosis and appropriate management contribute significantly to preventing adverse outcomes including mortality. Serology is widely used for diagnosing scrub typhus. Recent reports suggest that polymerase chain reaction (PCR) could be a rapid and reliable alternative. This study assessed the utility of these tests for scrub typhus diagnosis. Materials and Methods : Nested PCR to detect the 56 kDa antigen gene of O. tsutsugamushi was performed on blood clots from 87 individuals with clinically suspected scrub typhus. Weil-Felix test and scrub typhus IgM ELISA were performed on serum samples from the same patients. As a gold standard reference test was not available, latent class analysis (LCA) was used to assess the performance of the three tests. Results : The LCA analysis showed the sensitivity of Weil-Felix test, IgM ELISA and PCR to be 59%, 100% and 58% respectively. The specificity of ELISA was only 73%, whereas those of the Weil-Felix test and PCR were 94% and 100% respectively. Conclusion : Nested PCR using blood clots while specific, lacked sensitivity as compared to IgM ELISA. In resource-poor settings Weil-Felix test still remains valuable despite its moderate sensitivity.
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