General practice as a complex system: a novel analysis of consultation data

Complex systems have specific properties of robustness and self organisation which arise from interacting components within the overall system and which govern the system's behaviour. These are typically associated with a power law distribution of event sizes. Commentators have suggested that health systems are complex, but there has been limited quantitative investigation of this issue.

To test the hypothesis that consultation patterns in primary care follow a power law distribution typical of a complex system.

Analysis of 142,050 episodes of non-pathological back pain in routinely collected New Zealand national data. Calculation of the distribution of the duration and number of GP consultations for each illness episode. Secondary analysis of a published UK dataset of consultation rates for 44,000 patients in four general practices.

Number of consultations per episode of back pain demonstrated excellent fit with a power law in the full dataset (r2 = 0.96) and all but one subgroups (r2 = 0.90-0.99). The number of consultations per patient from four UK practices was suggestive of a power law distribution (r2 = 0.88-0.93).

Consultation patterns in general practice show measurable properties of a complex system. The consistency of the distribution across different population groups suggests that attempts to manage consultation patterns should focus on the whole system of patients, rather than upon individuals or subgroups of the patient population.