Rules on how samples are taken from patients have been changed following the death of an 11-month-old baby, an inquest has heard.

Yahya Khan died from a cardiac arrest caused by undiagnosed acute appendicitis at Lister Hospital in Stevenage on August 11, 2012, a coroner ruled on Tuesday.

His parents Mashood Shafiq and Ouzmad Ahmad had taken Yahya to see a GP on July 17 after he developed diarrhoea, was vomiting and had a high temperature. He was diagnosed with mild gastroenteritis.

Yahya’s symptoms persisted and they took him to Addenbrooke’s Hospital in Cambridge five days later, where he saw Dr Josfito Rodrigues.

Speaking at the inquest, Dr Rodrigues said: “I examined him completely and couldn’t find anything wrong. He had a high temperature but his mother told me that his stool was becoming semi-solid but I did not see this.”

Yahya was discharged from the hospital later that day but his condition did not improve sufficiently so he was then taken to Lister Hospital on July 29.

There he was seen by an out-of-hours GP and later on Dr Amin Salem, who suspected that he had gastroenteritis and ordered that a stool sample be taken – which failed to be sent to the lab – and kept Yahya in for four hours of observations before being discharged.

On August 11 he suffered a fatal cardiac arrest at his home in Woodcock Road, Royston, and was pronounced dead at Lister Hospital.

While giving evidence, Dr Shafiq said: “I am really disappointed at what has happened. People just followed a tick box approach and did not properly examine what was put before them. I feel that this approach has lost us our son.”

Coroner Edward Thomas said: “I want to let you know how sorry I am about your loss and to tell you that you and your husband did everything you could have done to revive him.”

Expert witness from Great Ormond Street Hospital Dr Joseph Curry said it was an extremely hard case to diagnose because there were no obvious signs of appendicitis but that if blood tests were carried out it would have shown a high white cell count that may have led to exploratory surgery.

Following Yahya’s death an inspection was carried out by East and North Herts NHS Trust, which runs Lister Hospital.

A spokesman for the Trust said: “We would like to reassure our patients that lessons were learnt when Yahya’s care was re-examined. The pathology computer system used by the Trust was upgraded in December 2012 and now includes an indicator to demonstrate whether a specimen has been received in the laboratory or not.

“Once again, we would like to extend our deepest sympathies to Yahya’s family.”