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Pool Testing

  • 16 Apr 2020

  • Now with the number of cases spiking and the fear of community spread in some areas the Indian Council of Medical Research (ICMR), on 14th April, 2020, issued an advisory for using pooled samples for testing of COVID-19 across the country.

Objective

  • The objective is to increase the capacity of the laboratories to screen increased numbers of samples using molecular testing for COVID-19 for the purpose of surveillance.

About Pool Testing

  • In a pooled testing algorithm, samples of multiple individuals are put together in a tube and screened through the Polymerase Chain Reaction (PCR) test.
  • In case the pooled test turns out to be positive, individual samples are tested, which is referred to as pool de-convolution.
  • If there’s no positive result, all individual samples in the pool are regarded as negative, resulting in substantial cost savings.

Criteria for Pool Testing

  • This method can be used in areas where the prevalence of COVID-19 is low, which means a positivity rate of less than two percent.
  • Pooling of sample is not recommended in areas or population with positivity rates of over five per cent.
  • According to the ICMR, more than two samples can be pooled together; the number should not exceed five samples to avoid sample dilution, which can lead to false negatives.
  • Samples of individuals with known contact with confirmed cases or healthcare workers should not be included in the pooled samples.
  • Deconvoluted testing (testing individual samples) is recommended if any of the pool is positive.

Benefits of Pool Testing

Cost and Resource Effective

  • It increases the capacity of testing and it saves a lot of resources — time, cost and manpower.
  • For instance, if a pooled sample consists of the samples of five individuals and it tests negative, the cost of four testing kits is saved and more number of people are covered with fewer resources.
  • But in case the sample tests positive, all individuals need to be tested separately.

Help in Tracking Community Transmission

  • Significantly, pooled screening can also help in tracking down the asymptomatic cases of the disease, thereby tracking community transmission.