06 October 2010
By Pritha Chatterjee
SOON after experts emphasised the urgent need to validate screening tests for chikungunya, the inaccurate results for leptospirosis have left doctors worried. The flaws of screening tests came to light after a series of samples underwent ELISA tests.
Dr Jayanthi Shastri, in charge of the Kasturba Hospital’s PCR laboratory, said: "The PCR test we offer at Kasturba gives hundred percent results, but it is a molecular test which is only valid within the first seven days of fever."
She added that since most patients do not report within that time period, diagnosis is mainly on the basis of screening tests. "Every private hospital or laboratory has its own screening kit. Each kit has its own degree of sensitivity–false postives or negatives,"said Dr Shastri.
According to her, several samples that have come to the civic hospital’s lab after screening have given contrary reports when verified with the standard ELISA test. Without divulging figures, she concedes these samples have come from civic hospitals and private laboratories alike.
Senior microbiologists say the dearth of any validating authority for screening tests has emerged as a serious problem.
"Any company can manufacture a screening test without any proof of reliability and sell it to patients and doctors alike.
There should be some mechanism to grant licence to these after verification with an ELISA test," says an HOD (microbiology) from a state–run hospital.
"The problem is very few laboratories are quipped with the ELISA test. So we need a validating body at the central or state level to fulfill this purpose." Currently the Drug Controller General of India (DCGI) which is the apex authority for passing drugs and vaccines in India, has no licensing system for diagnostic tests.
Unlike viral infections like chikungunya, where virulence is low, and treatment mostly symptomatic, doctors say the lack of a reliable diagnostic test for bacterial infections like leptospirosis is a matter of concern. "In Leptospirosis, early diagnosis can enable doctors to put patients on the right antibiotics. This can prevent complications that are often associated with the disease. The scanty cases we have been seeing this monsoon may definitely be attributed to problems with the screening test ,"said a doctor from KEM’s Preventive Social Medicine (PSM) department.