'Isolate if you have Covid-19 symptoms but test negative'

A director of public health is advising people to isolate if they have Covid-19 symptoms even if they subsequently receive a negative PCR test result.

GPs in the West said they were seeing "a stream of patients" who had received positive lateral flow tests, who went on to receive negative PCR results.

The UK Health Security Agency said it was investigating the cause.

But one Independent SAGE adviser has said self-isolating after a negative test may not be practical for some.

While it is understood lateral flow device (LFD) tests can sometimes produce a false negative, false positives are much rarer.

The UK Health Security Agency said it had been made aware of "some areas across the country" anecdotally reporting positive LFD results with subsequent negative PCR tests.

It added there was currently no evidence of there being any technical issues with LFD or PCR test kits in relation to those reports.

It said no test was 100% accurate, although the chances of a false positive result remained low.

A growing number of people have been taking to social media to report the phenomenon.

Many have been from Bath, Bristol and Swindon but it is also understood to be happening elsewhere in England.

Becky Reynolds, director of public health for Bath and North East Somerset Council, said the council was aware of the situation adding: "It is confusing [for people]. I think we just need to bear with it while the investigation happens".

Ms Reynolds said the advice they had been given was that "PCR are the gold standard" and officially a negative PCR means you do not have Covid.

But she said: "The advice is also to think about your local situation, do an individual risk assessment... so what is the likelihood that even though the PCR is negative, that you may still have Covid?

"If thinking it through there is quite a chance you have Covid, even if the PCR is coming back negative, then regard it as Covid and self-isolate."

Dr Lucy Pocock, a GP from Cadbury Heath Healthcare in south Gloucestershire, said: "Myself and my colleagues have seen a stream of patients with what we would consider very typical Covid symptoms.

"Several of these patients have done multiple lateral flow tests, all positive, and have then rightly gone on to do a PCR test, which has come back negative.

"The worrying thing here is that these people are all clearly symptomatic and with a very unexpected negative PCR result."

Unwittingly spreading Covid

Caroline, a teaching assistant from Bath, and her son Harry, 12, both tested positive on lateral flow tests three times this week and both received two negative PCR test results.

She said: "I've never had a line before on the lateral flow test and I've been testing twice a week, each week, because I work in a school.

"But this week I got a line and I had symptoms.

"I spoke to my GP as well and she said it was Covid, especially with the symptoms, and to self-isolate, which I have been doing.

"I think people need to know about this because otherwise they could be going out into the community and spreading it without realising because they've had a negative result."

Hayley Hodge, from Stroud, became ill with a temperature and a cough two and a half weeks ago.

"I took a lateral flow, as did my 14-year-old son, and they were both positive yet our PCRs were returned negative," she said.

"My mum then became ill and also tested positive on a lateral flow test but then was negative PCR.

"I thought I was going crazy as my research kept saying that although PCR's are the gold standard that lateral flow test false positives were extremely rare.

"Between our family we used a variety of test kits. Some were brand new and some have been around the house for a couple of months or more. So I don't think it is likely that it is faulty testing kits in our experience.

"I know people are now on the case so hopefully they will find answers soon."

'Can't access support'

A member of the Independent Scientific Advisory Group for Emergencies [SAGE], Kit Yates, has called for the situation to be looked into "seriously and rapidly".

The University of Bath professor continued: "Public health England have suggested informally that you should still self isolate even if you get a negative PCR test, especially if you have symptoms, although that isn't the government guidance.

"The problem with that is that if you don't have a positive PCR test, then you can't access the support for isolation that you might need.

"So telling people to self-isolate, even if they get a negative PCR test, might not actually be that practical for many people."

Chief medical advisor for the UK Health Security Agency, Susan Hopkins, said: "We have been made aware of some areas reporting positive Lateral Flow Test test results with subsequent negative PCR tests and we are looking into the cause."

She said it was vital to carefully read and follow the instructions for use on the test kit in order to avoid any incorrect readings.

Follow BBC West on Facebook, Twitter and Instagram. Send your story ideas to: bristol@bbc.co.uk