No test in medicine is 100% accurate, writes Dr Muiris Houston, Medical Correspondent, but best practice guidelines must be followed to minimise the risk of misdiagnosis
The case of the 51-year-old woman from the midwest whose diagnosis of breast cancer was delayed by 18 months is a reminder of the fallibility of medical science and the need to implement rapidly a new system of quality assurance standards for breast disease.
The fact that two separate biopsies were reported as negative, when in fact both were positive for cancer, does not engender confidence in our health system. Of particular note is that this latest incident involves both the public and private sectors of the health service, which will serve as a warning that the planned outsourcing of public diagnostic testing to the private sector must be implemented in a manner that prioritises quality and patient safety.
The woman's breast biopsies were performed in Barrington's Hospital, a private facility in Limerick. The tissue samples were then analysed in the laboratory at University College Hospital Galway (UCHG), a public teaching hospital. Crucially, this meant that the doctor who examined the woman clinically and the pathologist who looked at the sample did not have an opportunity to discuss the woman's case as part of a multidisciplinary conference.
Fortunately, the consultant in Limerick, using his clinical judgment and experience, asked for the biopsies to be reanalysed at a Cork hospital. However, had the patient attended the breast clinic at UCHG she would have undergone a triple assessment by a multidisciplinary team, and would have benefited from a full discussion of her case at the unit's weekly case conference.
This system, recommended as standard practice by the National Quality Assurance Group for Symptomatic Breast Disease Services, minimises the risk of a misdiagnosis. But no system can prevent or avoid misdiagnosis.
As modern consumers, there is a tendency for us to assume that medical tests are 100 per cent accurate. But they are not: every blood test, X-ray and biopsy result can be either falsely positive or falsely negative. A person with a false positive result does not have the disease even though the test suggests they do. False negative results occur in people who have the disease, but the test suggests they are disease-free.
The National Quality Assurance Group for Symptomatic Breast Disease Services, in a recent report, acknowledges this reality. Even in conditions of best practice, up to one in 20 women may be told that they do not have breast cancer following a fine needle biopsy, even though in reality they have the disease.
Notwithstanding this fallibility, all women with suspected breast cancer must be assessed in specialist, multidisciplinary breast units.
Not alone will it maximise their chances of an accurate diagnosis, they will also benefit from a team approach designed to give patients high quality, individualised treatment.