Coronavirus (COVID-19) protective measures: indicators and data

Core indicators and their use

Weekly new positive cases per 100,000 people

This indicator is defined as the number of people with a first positive test result, measured over a week, relative to population size.  The new positive cases number is based on the date the test specimen was taken.  There is a reporting delay in testing results, so data is drawn with a 3-day lag to allow for results to be available.

This indicator provides a valuable indication of the actual current spread of the epidemic.  This figure is most helpful when used as complementary to the forecast case rate.  The weekly total proposed aligns with the figures published on the PHS dashboard neighbourhoods site with a 3-day lag to allow for results to be available.

Percentage of tests that are positive over the past week

This indicator is defined as the 7-day average of the number of positive PCR tests divided by all tests carried out over the past week.  Local intelligence would be required where there are low numbers of tests.  There is a reporting delay in testing results, so data is drawn with a 3 day lag to allow for results to be available.

This indicator is important as it reflects both levels of testing and, by drawing on positive test results, can indicate the spread of the virus.

Projected weekly cases per 100,000 people

This indicator is defined as the projected number of cases per 100,000 people in two weeks’ time, provided by modelling from the SPI-M consensus.  The probability of an area exceeding 300, 150, 50 or 20 cases per 100,000 population is calculated.  A 75% or higher probability of exceeding a number of cases is used to help define what level an area is assigned to.

This indicator is important because it can be used to identify hotspots across Scotland where infections are likely to be high in two weeks’ time.  This gives an early warning of where there may be increases, which gives time to act to slow the rate of increase.

Projected Covid Hospital Demand

This indicator is defined as the current and projected occupancy of Covid hospital beds in future weeks. 

The Covid bed indicator will operate at NHS Board level.  It reflects system capacity and pressures on individual boards, factoring in well-established mutual aid arrangements at regional and national level.  Data currently used is based on recently-confirmed COVID-19 cases (within 28 days).  Work is ongoing with Boards and Public Health Scotland to explore extending this to include patients with COVID-19 for more than 28 days.  Pending finalisation, a definition of recently-confirmed Covid-19 cases will be used.

Projected Covid Intensive Care Unit (ICU) Demand

This indicator is defined as the current and projected occupancy of national Covid ICU beds in future weeks.

ICU will be assessed at a national level throughout the levels process, as the NHS Scotland service delivery model for ICU includes well-established mutual aid arrangements at regional and national level.  Covid ICU bed numbers equate to total patients in ICU with recently confirmed COVID-19 and those with COVID-19 for more than 28 days.