The BMC puts the total number of chikungunya cases in September at only 25,but doctors on the field say they have treated a lot more than usual this year. Experts attribute the discrepancy to the low sensitivity of the diagnostic tests available.
The commonly used rapid test method,which detects antibodies produced by the body,is not as sensitive to chingkunya as it is to dengue. Microbiologists say it does not always give correct results for chikungunya.
It is impossible to ascertain the extent of the infection,as the test results are inconclusive. A lot of the time it gives false positives and negatives,and unlike with other tests,there are no ways to detect these wrong results, says Dr Jayanti Shastri,laboratory head at Kasturba Hospital.
Samples collected in her laboratory in September will now be sent to the National Institute of Virology (NIV) in Pune for the stronger ELISA test. Though the virus does not have fatal or even dangerous manifestations,it is important that we get a true picture of the magnitude. There is an urgent need to validate this existing test,Dr Shastri says.
ELISA too detects antibodies but has a higher sensitivity and reliability. Not only the sensitivity,the rate at which a test gives false positives,or positive results for patients who may not be suffering from the viral infection,also determines its validity. The rapid tests for chikungunya unfortunately fail on both counts,said Dr Shastri.
Over the past month,doctors have relied mainly on symptomatic treatment. The antibodies are only detected after a minimum of 5-7 days,and even then the reports are not completely reliable. We have been mostly diagnosing it from symptoms like fever with joint pain,and administering treatment accordingly, said a doctor with KEM Hospitals preventive social medicine department.
If patients insist on a confirmed diagnosis and can afford the test at about Rs 600-800,we ask them to go ahead. But it is not essential,says general practitioner Dr Suhas Pingle.
It is high time we had an alternative test for chikungunya. Most doctors do not even bother with tests, said a microbiology head at a BMC hospital.
Dr Ravi Rananaware and Dr Sandhya Kamat.,deans of Nair Hospital and LTMG Hospital,say their hospitals do some tests for chikungunya but send most samples elsewhere.
The call for an affordable,alternative test comes amid a spread across the city. Last year there were cases in other parts of Maharashtra. I would say Mumbai is seeing such a high rate of chikungunya infection the first time in three years, says Dr Pingle.
Dr Pradeep Parikh,consultant at Breach Candy Hospital,says,Contrary to the trends in the first two weeks of September,chikungunya is no longer restricted to any particular part of Mumbai. We are getting a high rate of infections from all over the city. There is a decided jump from last year,though without any increase in virulence.