Thread by @saikirankannan

****Long Thread on #PoolTesting****

This is the time for India to increase the ratio of #Pool tests.

The number of #COVID19 cases in #India has seen a constant rise over the past two weeks. This has been concerning considering that most cities are gradually coming out...

...of the lockdown. Domestic flights have resumed operations and soon, we may see other relaxations coming into effect. Offices and factories are opening up across states and this may certainly lead to a new wave of cases being identified.
#COVID19India #PoolTesting

As of the morning of 27th May, the top four infected states in India, which are Maharashtra, Tamilnadu, Gujarat & Delhi amount to around 67% of the total cases recorded in India. But, the concern has also been the rising number of cases in states that were very much in control...

a fortnight ago. States like #Kerala, #Karnataka & #Assam have seen a spike in cases recently.

Testing coverage:
India’s testing numbers currently come up to 1.2 lakh samples a day. This includes both the public and private labs. The Government has designated...#COVID19India

a total of 610 labs of which 178 (29%) are private labs. Given the share of private labs, it is imperative that testing rates of private labs must increase more to achieve the government’s aim of having 2 lakh samples tested each day. Currently, private labs amount to...

only around 20% of the daily testing numbers.
With the rate of rise in cases seeing a steady increase across states, especially in the top four states, the testing numbers too need to rise accordingly to handle the backlog. There were reports of backlog...#COVID19India

in testing results, especially in major cities like #Mumbai and #Chennai. People with symptoms are unable to get themselves tested immediately owing to the queue of samples already in the pipeline at testing labs. #COVID19India #PoolTesting

With the resumption of offices and factories, it is logical that India will see additional cases. In order to handle the additional burden that may arise on the medical &testing infrastructure, India ought to upgrade its testing strategy and coverage. #COVID19India #PoolTesting

Anticipated problems:
The lockdown relaxations have already seen the discovery of new cases and spreads. Ever since the domestic flights resumed, India has already seen two cases of co-passengers testing positive after a flight. One was an Indigo flight from Chennai to Coimbatore

; the other was an Air India flight from Delhi to Ludhiana. This has resulted in the grounding of the airplane staff and monitoring of the passengers of respective planes. Cases like these may result in the formation of new clusters. #COVID19India #PoolTesting

Additionally, Auto factories like Hyundai and Maruti Suzuki have also seen closures upon resuming operations owing to their staff testing positive for COVID-19. This is a show stopper for an economy that is already reeling. #COVID19India #PoolTesting

While states like #Tamilnadu and #Maharashtra lead the charts for clocking the maximum number of tests and cases to date, states like #Gujarat & #WestBengal have a serious issue when it comes to case numbers and mortality rates. #COVID19India #PoolTesting

They have mortality rates of around 6% and 7% respectively, which is well above the national average of 2.8%. These states are woefully short when it comes to testing numbers and if they do not ramp it up, it may lead to a full-blown crisis. #COVID19India #PoolTesting

Pool testing:
Pool testing is a simple technique of collecting multiple swab samples of patients and testing them as one single specimen using the RT-PCR (Reverse transcription-polymerase chain reaction) mechanism. #COVID19India #PoolTesting

If the specimen tests negative, it implies that all samples part of the specimen are negative for COVID-19. If the specimen tests positive, it means at least one of the samples in the mixture is positive. #COVID19India #PoolTesting

In such cases, people whose swab sample mixture has tested positive will be then further tested individually.

The Lancet released an article on effective employment of Pool testing practices wherein up to 30 samples could be pooled together and tested.

thelancet.com/journals/lanin…

To test 30 samples together, the individual samples are first pooled into 3 sub-pools A, B & C of 10 samples each, and then a larger pool D of 30 samples is created from the 3 sub-pools. If the larger pool D is positive, the sub-pools A, B and C are analyzed... #PoolTesting

...and if not all of them test positive, then the specific sub-pool with positives can be further analyzed by individually testing the 10 samples that form that particular sub-pool. Say, Pool B and C test negative. #COVID19India #PoolTesting

This means all the samples that constitute these two pools have tested negative. So that leaves Pool A as the only positive sub-pool. Now, the 10 samples that constitute the Sub pool A can all be tested individually or can further be split into ...#COVID19India #PoolTesting

...sub-pools (Pool A1 & Pool A2) of 5 each to further determine where the positive sample lies, thereby greatly reducing the number of actual tests required to find positives. Among these, if Pool A2 tests negative and Pool A1 tests positive, we can only test Pool A1 samples...

individually. So as per the above example, only 11 tests were required to test a total of 30 samples. This method is similar to the binary sorting technique whereas we progress, the number of pools will increase and the size of the pools will decrease.#COVID19India #PoolTesting

Lancet suggests that pooling of up to 30 samples per pool can increase test capacity with existing equipment and test kits and detect positive samples with sufficient diagnostic accuracy.#COVID19India #PoolTesting

How can it help India?
The ICMR acknowledges the substantial cost savings this method offers and has released an advisory for the usage of pool testing. The advisory states the following:

#COVID19India #PoolTesting

1.The ICMR has limited the number of samples to 5 samples per pool. It has also suggested this mechanism to be used only in areas where the positivity rate (number of positive cases by total number of people tested) is less than 2%. #COVID19India #PoolTesting

2. In areas where the positivity rate is 2%-5%, sample pooling for PCR screening may be considered only in community survey or surveillance among asymptomatic individuals, strictly excluding pooling samples of individuals with known contact with confirmed cases, Health Care

3. The pooling of sample is not recommended in areas or population with positivity rates of >5% for COVID-19

*India currently has a positivity rate of around 4.70%.

Pool testing can be of great help in addressing clusters in offices and factories like the examples we referred

...to in the above sections. Housing societies, SMEs, MSMEs, Government offices, military camps, airport staff etc. can be subjected to pool testing to save a lot of time and effort.

Pool testing will also be highly useful to designate green zones. #COVID19India #PoolTesting

Some states like Uttar Pradesh have already been employing pool testing mechanisms in their overall testing strategy. But it remains to be seen how effectively it has been used and what have been the major learnings and advantages of using such a technique. #COVID19India

With the migration of laborers between states, Pool testing can greatly help identify infected people quickly and efficiently. A 1000 laborers, may not need 1000 tests. Given the scale of testing India is staring at, it is high time Pool testing becomes a mainstay... #PoolTesting

... of the testing strategy. Given the COVID-19 pandemic will continue to be a cause of worry for the rest of the year, pool testing is a technique that can be employed in regular intervals across workplaces, schools and colleges once they resume functioning. #PoolTesting

Regular pool testing offers a quick and effective way of detecting new clusters and outbreaks. Given the majority of cases in India have been asymptomatic, pool testing offers an easier way to home quarantine people and prevent the further spread of the virus. #PoolTesting

Global use of Pool testing:
Pool testing as a technique was first used during the Second World War to detect cases of Syphilis in the US Army. It was designed by a Professor named Robert Dorfman teaching at Harvard University. #COVID19India #PoolTesting

Pool testing has greatly benefited the medical field in the past and present. While COVID-19 has seen countries employ this mechanism with minor tweaks according to their requirements and necessity, pool testing has also been used effectively in the past during...#PoolTesting

.. the early stages of the HIV epidemic when the PCR test costs were quite high.
Pool testing has been used across the world for COVID-19. South Korea, one of the pioneers in bending the curve, used pool testing to test 10 samples at a time. This greatly increased their testing %

Similarly, I hope India can manage to use Pool testing effectively.
*** End of Thread***

#COVID19India #PoolTesting