Dr Shah added: "I'm probably sending a couple of patients to A&E a week because of results I suspect to be faulty. Since Synnovis took over pathology services for south-east London, it's pretty much been a catalogue of disasters.
"We're almost second-guessing the pathology system and it's something that never used to happen.
"You go to a shoe shop, you expect to buy a pair of shoes; you have a pathology service, you expect accuracy and reliability. That's not happening."
Southeast London Integrated Care Board said in a statement that tests requested by south-east London GPs alone amounted to about 10,000 a day, "with a number of logistical steps involved, from blood taking through to results reporting".
It said there had been "a number of incidents" since Synnovis took on pathology services for south-east London that had been driven by a "number of factors, including incidents that have impacted on the Synnovis service but which were outside of their control".
The statement continued: "You will also be aware that one of these incidents was a criminal cyberattack, the response to which was an extraordinary effort from multiple partners, including Synnovis, to maintain a viable service for our GP colleagues, while Synnovis undertook the significant task of rebuilding their systems from the ground up."
According to a statement released by NHS England in October, 10,152 acute outpatient appointments and 1,710 elective procedures were postponed as a result of the cyberattack.
The statement said: "The final stages of recovery following the cyber attack on pathology services provider Synnovis in June are almost complete, which means nearly all services are now up and running."
In its statement, Synnovis said it offered more than 6,000 different types of test, serving almost two million patients, six hospitals and 191 GP practices across 249 sites.
"While we understand that any error at all can cause patient and practitioner distress, erroneous Synnovis tests account for significantly less than 0.001% of the 150,000 tests we process per day."
However, these figures appear to include all Synnovis testing, including urine tests.
Synnovis added in its statement: "The provision of Synnovis's pathology services for GPs is enabled through a range of test-request and results systems and software, a significant portion of which predates the Synnovis contract and are provided by legacy third-party suppliers.
"We are very aware that this has been an extremely challenging and sometimes distressing period for patients and front-line NHS colleagues and are incredibly sorry for the inconvenience and upset caused to those affected."
For college student Kemi, her recent experiences have made her lose confidence in the health service.
She said: "I feel like as a young person, not being able to have access to reliable results sets the precedent that I can't have an independent health journey as a 17-year-old. It's hard to know where I can go from here.
"It might seem like it's just a blood test but it's serious. It can be a matter of life and death."