After Achilles

Contrary to the view that ‘using time as a diagnostic tool’ is ‘sloppy and idle’ and that general practice has ‘floundered’ as a result of such unhelpful phrases, we consider that general practice has struggled to provide a robust evidence base to confirm or refute the value of time as a diagnostic strategy.¹ One of the most important diagnostic tasks performed by the GP is discriminating between the majority of patients with minor, usually self-limiting, illness and the minority with serious disease. This was illustrated by a cohort of 2690 adults presenting with lower respiratory tract infections of whom 92% had recovered within 3 weeks and only 1.1% were hospitalised, none of whom died.²

In 2013 we proposed the hypothesis that the opportunity afforded by reviewing a patient over time substantially increases the total gain in certainty when making a diagnosis in low-prevalence settings (the ‘time–efficiency principle’) such as general practice.³ We argued that this approach safely and efficiently reduces the number of patients who need to be investigated in order to make a correct diagnosis for a single person. We predicted that the time–efficiency principle operates most effectively at low prevalence, typically up to 10%. It has since been noted as a widely used strategy in primary care. The Lancet Oncology Commission on primary care noted that adequate diagnosis requires time for symptoms to evolve; emphasising that, although symptoms are common, cancer is rare.⁴ The time–efficiency principle has also been noted as an effective strategy for sifting common symptoms such as headache.⁵

What is required now is for the time– efficiency principle to be robustly evaluated, preferably by focusing on prospective studies. It is vital that we advocate the optimum number of consultations before referral rather than a simple view that quicker is always better.⁶ This may help us to understand why GPs continue to use these strategies and thus lessen over-diagnosis, despite government-led calls for more referrals and investigations. GPs need academic and College support to tolerate uncertainty appropriately, aided by their discerning and continuing use of time effectively and thus efficiently.