BENGALURU: There is a huge disparity between the numbers provided by the state government and a surveillance result by doctors at St John’s Medical College regarding those affected with dengue.
Dr B G Prakash, Surveillance Head of the Health Department, says that their number of 3,000 affected in the state is correct. The surveillance results show a higher number at at least 56,000. The state numbers are the numbers of confirmed cases.
Doctors at St John’s Medical Hospital have counted the number of dengue cases at the hospital in the last year till October 2015. It is 28,000; the number was extrapolated to include all other hospitals in the state and the doctors say the actual number could be double or triple of 28,000.
Prakash told Express, “Our numbers of the dengue affected is around 3,000 in the state. They are the correct numbers.” He added, “There is a protocol by WHO to confirm dengue. We get the number of confirmed dengue cases reported to us by private or public labs. They use two confirmatory tests NS1 and IGM to find positive cases.”
Dr Anita Shet, Professor at Department of Pediatrics in St John’s Medical College Hospital, told Express, “Global Mapping Studies show that India clearly has a high burden of dengue infection. Geo-statistical modelling coupled with actual case studies from Madurai district, estimated an annual average of almost 5.8 million clinically diagnosed dengue cases in the country between 2006 and 2012. This estimate was almost 300 times the officially reported numbers for the same period.”
Prakash goes into details of the tests, “There are diagnostic tests that do not confirm dengue but are general tests for all viruses. Their specificity and accuracy for dengue are not accurate. Government of India has given us written directions that say we must not include numbers that test positive for the diagnostic tests.”
Anita felt that the study looked at ‘clinically diagnosed dengue’ where diagnosis was based on the doctors’ assessment while the ‘reported cases’ were based on laboratory diagnosis.
She adds, “One way to overcome the discrepancy could be by using one or more serial rapid tests, rather than rely on the ELISA test alone for confirmation.”
Atul Kumar Tiwari, Principal Secretary to Health and Family Welfare Department and Medical Education said, “I dont want to get into a debate on this.”
Less Takers for ELISA
There are two common tests; one is called NS1/IgM ‘rapid’ test. Most patients are diagnosed as having dengue after this test turns out to be positive. This is an easy test. For official reporting, a more sophisticated test called ELISA is necessary for diagnosis of dengue. This is done in higher-level labs, as well as in the national reference centres. The test requires skilled hands and carefel sample handling. This phenomenon can perhaps explain why relatively few patients are officially diagnosed as having dengue. Anita says, “We found that the rapid test has a sensitivity and specificity of >95 per cent when compared to the official ELISA test. The ELISA test costs about `250 while the rapid test costs about `80. We are talking with the state government and hopefully will be able to use the rapid tests for reporting cases.”