MEDICAL MATTERS:Symptom flagging is a long-established strategy in physical medicine, but does it work, asks MUIRIS HOUSTON
READERS WILL be familiar with the work of Drogheda GP, Dr Harry Barry, through my writing and indeed his occasional guest column in Healthplus. He is the author of two groundbreaking books on psychological illness based on the concept of "flagging the problem".
This is a reference to his use of flags of different colours to identify mental health issues such as depression (a red flag) and anxiety (a yellow flag).
Symptom flagging is a long- established strategy in physical medicine. Doctors refer to red flag symptoms as ones that should alert the physician to the possible presence of cancer and other serious illness.
Among these alarm symptoms are passing blood in the urine (haematuria), coughing up blood (haemoptysis) and experiencing difficulty swallowing (dysphagia).
One of the reasons for doing this is in recognition of the fact that the number of cases of serious illness seen by a general practitioner each year is relatively small. In a family practice with a typical list size of 2,000, a GP will see just seven new cases of cancer, and five to six new heart attacks each year.
There is an immense challenge, therefore, to identify those who might have serious disease such as cancer, especially when it has been shown that up to 40 per cent of patients who attend primary care clinics recover from a minor illness without specific treatment.
So how do family doctors deal with this uncertainty? They use questions thought to have a high predictive value in ruling out serious disease: in reality, much of this involves the art of medicine and the use of personal heuristics by individual doctors.
More recently, health systems have laid down ground rules under which people with “red flag” symptoms must be able to access specialist diagnostic services within a specified timeframe.
However, there is as yet no evidence that adopting this common sense approach actually results in a more rapid diagnosis of cancers at a more treatable stage.
Researchers at King’s College London School of Medicine have assembled the world’s largest primary care database. In 2007, they published a paper designed to see how accurate “alarm symptoms” were in diagnosing cancer in a general practice setting. They found the risk of a cancer diagnosis in the three-year period after a patient presented with blood in the urine was 8 per cent in men and 3.7 per cent for women.
Coughing up blood produced figures of 8 per cent and 4.5 per cent respectively and for patients who experienced blood loss from the rectum, the risk of cancer was 2.7 per cent in men and 2.1 per cent in women.
The good news from these figures is how few people with worrying symptoms actually have cancer. The bad news is how poor “red flag symptoms” are at predicting the risk of cancer and how many people must undergo urgent and invasive investigations to pick up the few with a malignancy.
Of course, cancer is not the only serious illness associated with these symptoms. Blood in the urine could signal the presence of a kidney stone, inflammation of the kidney, a urinary tract infection or menstrual disorders. Someone who is having difficulty swallowing food could have an inflamed stomach or gullet, a hiatus hernia, a peptic ulcer or the connective tissue disease scleroderma.
The Kings College group then looked at some alarm symptoms to see how well they predicted other serious illness. The results, published in this week's British Medical Journal, show a general link between serious illness and increasing age in those who presented with a red flag symptom. More specifically, for those patients investigated after coughing up blood, about a quarter were found to have either cancer or another serious illness. For someone who came to their family doctor with difficulty swallowing, about one in five were found to have some form of serious illness.
This puts a better gloss on the value of using red flag symptoms as clues to serious illness and as an indication to investigate the problem more thoroughly. It also places the concept of “watchful waiting” in context and, according to the authors, their results suggest it may be time to consider replacing it with one of “timely testing”.
Dr Houston is please to hear from readers at mhouston@irishtimes.com but regrets he is unable to reply to individual medical queries