Public Health Bulletin

Testing the City and Hackney population for coronavirus

18 September 2020, No. 301


Pillar 2 testing in the community started at the beginning of April and has been steadily increasing. For the 14 complete weeks from the 6th June to the 11th September, 25,331 valid tests were performed in City and Hackney residents. A further 410 tests were registered as void in this period. 

The rates of testing have been increasing since June and the positivity rate has fluctuated over the period from June to the second week of September 2020 - the trends in positivity rates coincide with the trend in the number of new cases in City and Hackney over the same time period. The proportion of asymptomatic residents who have had a test increased over the summer months and has declined from late August.

Rates of testing 

The rate of pillar 2 testing per 100,000 in City and Hackney residents and coronavirus cases identified from these tests (positivity as a percentage) is described in Figure 1. The rise in positivity in July reflects the greater number of cases in the north of Hackney at that time.

The increase in the rate of testing particularly over the last two weeks of August may be due to an increase in demand as well as greater capacity at the mobile test units. 

Figure 1: Rate of pillar 2 testing per 100,000 population and positivity percentage by week

Data source: Public Health England, positive and negative pillar 2 tests and cases identified by pillar 2.

Location of tests and prevalence of symptoms

Data on whether a person had symptoms when the test was taken was available for 97% of tests. The trend in the percentage of tests with no symptoms shows a gradual increase until the end of August when there is a notable decline. Note that symptom data were missing for many of the tests in early June (Figure 2).

Data on the location of the test were available for 99% of pillar 2 tests. The percentage of pillar 2 tests registered in care homes across the time period ranged from 2% to 11%. There was a significantly higher percentage of testing in care homes at the beginning of June and in the first two weeks of July compared to the following 7 weeks. The percentage then starts to rise again at the beginning of September. The percentages of tests from home test kits (range 39% to 54%) have declined gradually from June to September and conversely, the percentages for those registered in test sites (range 36% to 54%) have increased (Figure 2).

Figure 2. The percentage of tests registered in different locations by week and the percentage of tests that were asymptomatic in the same week

Data source: Public Health England, positive and negative pillar 2 tests and cases identified by pillar 2. The Percentage of tests with no symptoms and Percentages of tests undergone in different locations were calculated excluding missing data. Note: some 19% of tests were registered in local or regional test centres in Newham, Greenwich, Edmonton and Redbridge.

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