Enhanced Surveillance of COVID-19 in Scotland
Population-based seroprevalence surveillance 30 September 2020

About this release

This release by Public Health Scotland results and methodologies of the serology surveillance programme. The serology work stream aims to estimate the proportion of people who have antibodies to coronavirus ("seroprevalence") in the general population of Scotland and to see if this changes over time.

Main points

• The proportion of people attending community healthcare settings who had antibodies to coronavirus is estimated to be 4.1%, 3.4%, 3.9% and 3.7% across each four-week period of the study. Between week commencing 20^th April and week commencing 3^rd August the proportion varied each week between 1.9% and 6.8% (across these weeks we can be 95% confident that the value lies between under 1% and 10%). Further analysis showed no significant trend across the study period (p=0.796).
• Proportions among males and females showed similar patterns across the study period.
• When compared by age, proportions were highest in the 0-19 years and 40-59 years age groups.
• The proportion of blood donors who have been infected with coronavirus in the Scottish population lies between 1% and 7%. Between week commencing 29^th June and week commencing 3^rd August the prevalence of coronavirus was estimated to be 3.1%. Further analysis showed no significant trend across the study period (p=0.257).

Background

Since week commencing 20^th April, blood samples, originally collected for other clinical reasons in community healthcare settings, have been obtained from regional biochemistry laboratories in six NHS Boards: Greater Glasgow and Clyde (GGC), Grampian, Highland, Lanarkshire, Lothian, and Tayside. Fife, Shetland and Forth Valley began submitting samples from week commencing 15^th June. Approximately 700 samples are now collected each week. Laboratories select specific numbers of samples by age and sex to achieve a representative sample based on the age and sex structure of the general population in that NHS board. Samples are anonymised and sent to the Scottish Microbiology Reference Laboratory in Inverness for testing. Seroprevalence rates have been adjusted for the accuracy of the antibody test. The results presented here cover the phase of the project between week commencing 20^th April and week commencing 3^rd August (i.e. up to and including 9^th August) when 9,809 samples had been received from the nine participating NHS boards.

Samples originally collected from blood donors have been retrieved and tested by the Scottish National Blood Transfusion Service (SNBTS) since week commencing 29^th June. Approximately 500 samples are collected each week from 12 NHS Boards (excluding Shetland and Western Isles). Seroprevalence rates have been adjusted for the accuracy of the antibody test. The results presented here cover the phase of the project between week commencing 29^th June and week commencing 3^rd August when 3,228 samples had been collected by SNBTS.

The Centre for Virus Research (CVR) at the University of Glasgow have also been retrieving blood samples, originally collected for other diagnostic purposes in hospital and community healthcare settings, and stored at the Queen Elizabeth University Hospitals biorepository since week commencing 9th March. Samples are anonymised prior to testing at the CVR. Samples relate to people who live in the Greater Glasgow and Clyde areas only. By week commencing 3^rd August, a total of 6,635 samples had been collected by CVR. These data are currently being analysed and used to validate our results from the regional biochemistry laboratories and will be published at a later date.

Further information

The next release of this publication to be confirmed.