Biomedical scientist Alexander McLauchlan was working out-of-hours on the night Kathryn Beattie was admitted to the Victoria Infirmary in Glasgow.
He tested samples that were sent to the lab and reported the results but said it was “custom and practice” not to look at a test known as a blood film – which would have showed up the leukaemia – outwith normal hours.
Mr McLauchlan was giving evidence at a fatal accident inquiry into the death of Kathryn, who died at the Southern General Hospital in Glasgow on 21 June, 2004, after brain surgery.
The inquiry, at Glasgow Sheriff Court, was previously told she had suffered from mild flu-like symptoms days before her death and was started on antibiotics. By that weekend, she felt better.
But she was taken to hospital after telling her mother she wanted to say something but the words would not come out, and her family wanted her to be checked.
After a brain scan showed bleeding, she was transferred to the Southern General for surgery but died later that day.
A blood film test – where blood is pressed between two pieces of glass, stained and analysed – would have been carried out if she had gone to hospital during the day.
Talking about blood films being taken out of hours, Mr McLauchlan told the hearing: “They are prepared ready for staining the next morning – that’s what happens every night when we are on call.
“Unless a member of staff phones to say, Can you look at a blood film for ABC, that would be done.”
He said Kathryn’s blood results, including a low platelet count, would have led him to look at a blood film if it had been during normal working hours.
The inquiry continues.