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| GMC Srinagar Microbiology dept tested 37,000 Covid-19 samples in last three months at CD Hospital, 2000 returned positive | | |
EARLY TIMES REPORT
Srinagar: The post graduate department of Microbiology, GMC, Srinagar started real time reverse transcription polymerase chain assay(RT-PCR) for detection of SARS-CoV-2 ( the virus that causes COVID-19 )in the BSL-3 lab of the microbiology department at Chest disease hospital from March 14th,2020. Till now our lab has tested around 37,000 samples and reported around 2000 positive cases(5.4%).
The preferred testing method for SARS-CoV-2 is the real-time reverse transcription-PCR (RT-PCR) test [ J Clin Microbiol 58:e00512-20]. The RT-PCR positivity begins from day second and maximum positivity is found between day 5-7 of the infection and the positivity decreases thereafter. Low levels are detected till day 15th also and finally become undetectable beyond that.
A doctor at GMC said, "Those patients who test positive initially and later test negative on retesting after 24hrs or more are actually in later part of the disease during the initial test itself and on subsequent tests they are in a stage where RNA is undetectable. The same applies to samples from Kashmir nursing home, Kulgam and Pulwama where the gap between the initial positive tests and negative retests was more than 24 hrs".
He adde, "Reports have been published about the results coming negative on first retest and positive on second retest of a confirmed positive case. The experts say it is an evolving disease and positivity has been reported even on day 25th [Expert review of Molecular Diagnosis,Science,The Wire].Test positive by RT-PCR holds more weight than the test negative by RT-PCR because this test has higher specificity(more than 95%) but moderate sensitivity(71-98%)".
A single negative test is not to be used as a rule out test in patients ( particularly symptomatic)[BMJ,12 May,2020]. Reasons for false negativity can be amplification inhibitors or insufficient organism in samples due to in appropriate sample collection, transport or handling. Moreover, false negative tests are a bigger problem than false positive tests as these patients can be silent spreaders of the disease, he added.
He further said, "Though initially we used to test samples from all the districts of south Kashmir and Srinagar district, besides and SMHS associated hospitals (GBpanth hospital, LD hospital, Superspeciality hospital,psychiatry hospital and bone and joint hospital), but when the travel ban was lifted our sample load increased tremendously as the districts which were initially sending their samples to SKIMS were also directed to our lab i.e the districts of north Kashmir and Budgam".
"So in the beginning of this month we were almost catering to whole of Kashmir and in addition receiving samples of the returnees and from Jammu also. It is only from 3rd june that we are receiving samples from three districts (Ganderbal,Kulgam and Pulwama)only besides SMHS and all associated hospitals. Regarding the increase in positivity at a particular time, we were reporting just under 2000 tests in 24 hrs so naturally the total number of positives reported were higher", he added.
He further said, "At present we are receiving around 500 samples each day so the number of positive cases being reported has come down proportionately. Regarding the said controversial sample, the run of the same was rechecked initially by the senior faculty members of the department and later on this run file was sent to the National Institute of Virology, PUNE for rechecking who have rechecked our run file and given a positive confirmation of our already reported result". |
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