Could Pooled Testing help Covid-19 Pandemic ?

In the current global Covid-19 pandemic scenario, to control the disease spread, timely identification of positives is extremely important. Therefore, the optimal usage of available resources like testing kits, manpower play a very crucial part. Pooled testing procedure which is a procedure where individual specimens like blood or urine samples are pooled into groups to test for a binary response- for e.g. Covid positive or Covid negative, will be useful in testing large populations with limited resources. In this procedure, if a specimen sample of the pool tests negative, then all individuals within it are diagnosed as negative. If it is found positive, then retesting within the pool is done to detect the positive individuals. Since, pooled testing is currently not being followed for Covid testing, the simple testing methods could be implemented taking into account risk factors like age, comorbidities, lifestyle etc.

For e.g. Consider a study on 100 random patient samples for an infectious disease who were also individually tested. The patient samples were pooled in 20 pools of 5 patient samples each. Of these 8 individual samples tested were found to be positive which were spread across 6 pools. Six pool samples were positive and the remaining fourteen samples were negative. All the samples of these 6 pools were again tested individually. So, a retesting of 30 patient samples were done. Despite this, the entire population of 100 patients were covered in 50 tests (20 pools samples followed by 30 individual samples).

This simple method gives a 50% reduction in the number of tests done, thereby optimising test kits, human resources and time which in turn helps in early quarantine and treatment of patients resulting in the control of the spread of the disease.

There is an alternative method: From the example above, 6 were positive pools each containing 5 samples each. Instead of testing all the 30, each positive pool of 5 samples could be split into 2 sub-pools of 2 and 3 patients and the same procedure can be repeated. Due to this binary split, a further 50% reduction in testing can be expected. That would mean approximately 25 tests will only be required instead of the original 100 tests since, the study started out with 100 individuals resulting in four fold increase in efficiency of testing.