Distinguishing variation in referral accuracy from referral threshold: analysis of a national dataset of referrals for suspected cancer

Objectives: To distinguish between variation in referral threshold and variation in accurate selection of patients for referral in fast-track referrals for possible cancer. To examine factors associated with threshold and accuracy and model the effects of changing thresholds.

Design: Analysis of national data on cancer referrals from general practices in England over a five-year period. We developed a new method to estimate specificity of referral to complement existing sensitivity. We used bivariate meta-analysis to produce summary measures and described practices in relation to these.

Setting: 5479 GP practices with data relating to more than 50 cancer cases diagnosed over the five years.

Outcomes: Number of practices whose 95% confidence regions for sensitivity and specificity indicated that they were outliers in terms of either referral threshold or decision accuracy.

Results: 2019 practices (36.8%) were outliers in relation to referral threshold compared to 1205 practices (22.0%) in relation to decision accuracy. Practice age profile, cancer incidence, and deprivation showed a modest association with decision accuracy but not with thresholds. If all practices shared the referral behaviour of those in the highest quintile of age-standardised referral rate there would be a 3.3% increase in cancers detected through fast track pathways at the cost of a 36.9% increase in urgent referrals.

Conclusion: This new method permits variation in referral to be described more precisely and quality improvement activities to be targeted. Changing referral thresholds without increasing accuracy will result in modest effects on detection rates and a large increase in demand on diagnostic services.