Bengaluru, Oct 24: The state government hopes to save costs on Covid testing by adopting pooled sampling. In this process, instead of testing just one sample in one test tube, five samples are used.
However, this can be done only when there are greater chances of samples being negative, since, if a sample pool tests positive, then each sample has to be individually tested again.
Now, with 10 districts of Bidar, Gadag, Raichur, Koppal, Kalaburagi, Yadgir, Ramanagara, Shivamogga, Chamarajanagar, and Kolar, having less than 5% weekly positivity rate, the state has allowed pooled sampling here.
However, in the rest of the 20 districts, individual tests will continue till they have a weekly average positivity rate of less than 5%. The government pays Rs 800 for every sample’s RTPCR test in a private lab. In Karnataka, 65% of labs are private and more than one lakh tests are done at government and private labs.
In Ramanagara district, which has a TPR of 4.1%, district surveillance officer Dr Kiran Shankar said, “We have a target of testing 800 samples with RT PCR everyday.”
“While pooling samples, we will make sure they are of low risk categories and not SARI, ILI or of patients with comorbidities. In pooling, the cost incurred on reagents added to samples and consumables will come down,” he said.
“Earlier, we would test only 96 samples in one cycle, which would take two-and-a-half hours. Now, we can pool and test 480 samples and get the results in a short time.”
Dr C N Manjunath, state nodal officer for Covid-19 testing, explained the process. “If Ramanagara has a target of testing 800 samples everyday via RT PCR, instead of using 800 test tubes for 800 samples separately, 160 tubes will hold 800 samples as each tube will have five samples.”
Dr V Ravi, Senior Professor and Head, Neurovirology, Nimhans, and member of State Covid-19 Technical Advisory Committee, told DH, “Increased volume and decreased costs are the benefits of pooled testing. Cost is reduced while doing RNA extraction.”
Koppal has so far done 75,235 RT PCR tests. It’s weekly test positivity rate (TPR) is 3.7%. Vikas Kishor Suralkar, deputy commissioner, Koppal told DH, “We have been pooling samples even when our TPR was more than 5%. But I agree that the likelihood of a positive pool is less when the TPR is less than 5%. Even if some pools should come positive and we have to test all five samples individually again, one extra test doesn’t increase the cost much. But avoiding five individual tests, when a pool comes negative, greatly reduces the cost.”