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Friday, July 10, 2020

Uttar Pradesh: Pool sampling hitch to ramping up of testing

Though 10-sample pool testing is allowed, it is not being followed extensively to avoid burdening labs

Written by Avaneesh Mishra | Lucknow | Published: June 2, 2020 10:51:52 am
Uttar Pradesh: Pool sampling hitch to ramping up of testing People throng Aminabad market in Lucknow on Monday as shops reopened. (Express Photo by Vishal Srivastav)

At a time the UP government is focusing on increasing its daily testing capacity to 20,000 Covid-19 samples by June 20, an official directive allowing 10 samples to be pooled together, instead of five, is not being followed extensively amid an increase in the test positivity rate in the last few weeks. This may hinder the efforts to ramp up testing.

If a pool tests positive, then the individual samples are examined to find out which one has the virus that causes Covid-19. According to an expert, positive 10-sample pools place an added burden on laboratories, and slow down the process of examining samples. At present, there is no fixed criteria to determine which places will have specimens placed in a 10-sample pool, and which areas will have five-sample pool tests.

The health department is dependent on pool testing to increase the testing capacity. In this method, swab samples from the mucous membranes of the nose or throat of a specified number of people are combined in a test tube and tested for the virus that causes Covid-19 using the real-time reverse transcription-polymerase chain reaction (RT-PCR) procedure, which is also used to test individual samples.

The samples from the nose or throat are first pooled together by suspending them in a solution in proportions specified. The remaining samples are then labelled and kept separate. A pool is tested, and if it is negative then all the samples in the pool are cleared. If it is positive, all the individual specimens are tested.

Though it has been more than two weeks since the UP allowed laboratories to add 10 samples in a pool, instead of five, almost 90 per cent of the daily pools being analysed consist of five samples.

As per information provided by Principal Secretary (Health) Amit Mohan Prasad, on Sunday 958 pools were tested. Out of them, 847 consisted of five samples and the rest 111 were of 10 samples each. An additional 3,207 samples were tested separately.

Dr Amita Jain, the Head of the Department of Microbiology at King George Medical University (KGMU) in Lucknow, told The Indian Express that five-sample pools were still being examined due to the increase in positivity rate in the past few weeks. KGMU is one of the biggest mentor institutions for Covid-19 treatment centres, and is examining almost 20 per cent of the daily samples in the state.

“Positivity rate in the state has increased since almost the same time it was decided that 10 samples can be added in a single pool. At the end of the day, it is for the labs to decide what suits them. What we are doing is that if the samples are from a low-prevalence area then we are adding 10 samples in one, but for samples from the high-prevalence area, five samples in one pool is better for us. If a pool of 10 samples is tested positive, it is double the work we have to do in comparison to a pool of five samples testing positive. This also increases the waiting time for the person sampled,” said Jain.

Out of the 847 five-sample pools tested on Sunday, at least 100 turned out to be positive. As a result, all 500 samples in these pools had to be re-tested. Similarly, 20 of the 111 pools of 10 samples each turned out to be positive, and all 200 samples in them were tested again. On Saturday, 892 five-sample pools had a positivity rate of 13.78 per cent, while 121 pools of ten samples each showed a 21.48 per cent positivity rate.

On May 15, state health officials had confirmed that following the approval of the Indian Council of Medical Research (ICMR) to pool maximum 25 samples in one, the state would increase the number to maximum 10 samples. Before that, the limit was five samples per pool.

On Sunday, Chief Minister Yogi Adityanath directed the state officials to set up a testing lab in each district, and announced that the state would now test more than 10,000 samples a day.

Health officials have also been directed to push up testing capacity to 15,000 samples by June 15, and 20,000 five days later. Amit Mohan Prasad said the health department was continuously working to expand the testing capacity, and was now providing Truenat machines to each district.

“Till now, we had 20 such machines which were provided to 20 districts and 21 more are coming today via state plane. The rest of the 34 machines are expected to arrive in the next three to four days. When these machines are available, even the districts with no Bio Safety Level 2 labs will be able to start testing Covid-19 samples,” said Prasad.

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