No significant change was made to treatments using blood products in Scotland in 1983 because there was only a “small risk” of Aids transmission, an inquiry has heard.

Thousands of patients across the UK were infected with HIV and hepatitis C via contaminated blood products in the 1970s and 1980s.

About 2,400 people died in what has been labelled the worst treatment disaster in the history of the NHS.

Scotland was the first part of the UK to hold a public inquiry into the scandal – with around 3,000 estimated to have been infected there – but it only took place in 2009 and did not report until 2015.

A UK-wide inquiry was formally established in July 2018.

Professor Christopher Ludlam, a consultant haematologist and reference centre director at the Royal Infirmary of Edinburgh from 1980 to 2011, appeared before the UK-wide Infected Blood Inquiry on Wednesday for his second day of giving evidence remotely.

Jenni Richards QC asked him: “What if any steps or changes were taken at Edinburgh in 1983 in response to the understanding that there was a risk to hemophiliacs from Aids?”

He replied: “At that time, as you know, we were treating virtually all patients with either cryoprecipitate or NHS Scottish-produced, PFC-produced, Factor VIII concentrate.

“And we were taking measures to reduce the risks to keep as low as possible the risk of hepatitis being contracted in patients, particularly those who weren’t infused very often or if possible in small children.

“I was aware, made inquiries that there were no cases of Aids having been reported in the Scottish population and so I made the assumption that the likelihood of there being a transmissible agent was low in Scotland.”

Prof Ludlam said he contacted the infectious diseases unit at Ruchill in Glasgow, which had no knowledge of cases despite making other inquiries.

He added: “On that basis I thought that the risk was small but not zero.”

Ms Richards then asked: “Does it follow from the answer you’ve just given that there was no significant change of approach to treatment in 1983 and 1984 on your part because you assumed for the reasons you’ve given that the concentrates you were using were safe?”

Prof Ludlam replied: “Relatively safe, I think that’s fair, yes.”

Ms Richards also asked about his understanding of the risks of transmission of Aids in both cryoprecipitate and the factor concentrates.

No-one drew to my attention any individuals, any known cases of people developing Aids who could have been blood donors

Prof Ludlam said: “In England, by 1983 there were individuals who had Aids in the general population so there was a risk that some of those potentially could present as blood donors.

“Therefore there was a risk that NHS concentrates and cryo and other products could be infected.

“In Scotland, as I mentioned I wasn’t aware, nor were the authorities I consulted, and no-one drew to my attention any individuals, any known cases of people developing Aids who could have been blood donors.”

Ms Richards then asked if the professor thought, in February 1984, whether NHS concentrates were safer than cryoprecipitate or not.

He replied he found it a difficult question to answer because he felt it was likely the risk of infection in the donor population was low.

The professor described hepatitis B as an example of a virus that is very infectious, saying you need “only a very small number of virus particles to infect an individual”.

Prof Ludlam also told the inquiry “there was a lot of uncertainty at this time and the puzzlement in some people’s minds about the viral aetiology of Aids extended until at least 1992”.

The inquiry continues before Sir Brian Langstaff on Thursday.