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We came across an interesting article titled Serological Evidence of Scrub Typhus among Cases of PUO in the Kashmir Valley- A Hospital Based Study by Farhana A et al., . In their hospital-based cross-sectional study, authors have studied 162 serum samples of patients with Pyrexia of Unknown Origin (PUO) for scrub typhus by Weil-Felix Agglutination Test (WFT) and Enzyme Linked Immunosorbent Assay (ELISA).
However, following issues and concerns need to be addressed:
Kindly find below the response to the comments and queries raised against our article entitled “Serological Evidence of Scrub Typhus among Cases of PUO in the Kashmir Valley-A Hospital Based Study”.
1. We have in our study made the exclusion criteria very clear. The clinical presentation of scrub typhus is non-specific and varies from undifferentiated febrile illness to multiorgan faliure. The diagnosis actually requires a high index of clinical suspicion with favourable ecology and climate. The article publised by Dr. Manju Rahi, whose reference has been cited in the comments, has neither been endorsed by the Ministry of Health and Family Welfare nor circulated as official guideline for diagnosing the disease.
2. We have mentioned in our study that the sensitivity and specificity of Weil-Felix test are low in view of which the results should be confirmed with other substantial tests like ELISA etc. Nonetheless the sensitivity and specificity of WFT is 30-60% and 45-100% respectively and it can serve as a useful aid in diagnosing rickettsial infections especailly in resource constraint settings as it is afordable, easily available, technically non-demanding with results available next day.
3. We took samples from patients who had been clinically worked up for and found negative for respiratory tract infections including tuberculosis, pneumonias etc., and urinary tract and gastrointestinal tract infections, malignancies and other associated illnesses. Such a workup included and was not limited to laboratory paramaters other than those that come under microbiology. Enteric fever and brucellosis are endemic in our valley and were thus rightfully excluded. It is uneconomical and a waste of time to exclude diseases that are rare or non-existent in the valley.
4. The cut off OD value was calculated as per the manufacturer’s instructions on the kit and has been mentioned in the paper.
5. The samples were collected from patients with PUO of 7-20 days duration. We have in our study mentioned some of the limitations which are self explanatory. Indeed the serological response to disease including rickettsial infections is as explained in literature and hence there are limitations of serology in the early diagnosis of diseases but newer tests like IFA, PCR which can confirm the presence or absence of scrub typhus are not available everywhere.
6. Treatment was given to suspected cases and/or those diagnosed by serological tests.
Scrub typhus or for that matter any other rickettsial infection requires a high degree of clinical suspicion. In our study, we made an effort to find out whether or not scrub typhus is a valid entity in the differential diagnosis of PUO cases in our state. Since, it is the first study from Kashmir Valley, it was meant to draw attention to the possibility of any such illness in our population and serve as a road map for further more detailed research in this area.