Diagnosing Type 2 diabetes before patients complain of diabetic symptoms—clinical opportunistic screening in a single general practice

In the UK, patients normally see their general practitioner first and 86% of the health needs of the population are managed in general practice, with 14% being referred to specialist/hospital care. Early diagnosis is the privilege of general practice since general practitioners make most medical diagnoses in the NHS. Their historic aim has been to diagnose as early as possible and if possible before patients are aware of symptoms. Over time, diagnoses are being made earlier in the trajectory of chronic diseases and pre-symptomatic diagnoses through tests like cervical screening. Earlier diagnosis benefits patients and allows earlier treatment. In diabetes, the presence of lower HbA1c levels correlates with fewer complications. Methodologically, single practice research means smaller populations but greater ability to track patients and ask clinicians about missing data. All diagnoses of type 2 diabetes, wherever made, were tracked until death or transfer out. Clinical opportunistic screening has been undervalued and is more cost-effective than population screening. It works best in generalist practice. Over 19 consecutive years, all 429 patients with type 2 diabetes in one NHS general practice were analysed. The prevalence of type 2 diabetes rose from 1.1% to 3.0% of the registered population. Since 2000, 95.9% were diagnosed within the general practice and the majority (70/121 = 57.9%) of diagnoses were made before the patients reported any diabetes-related symptom. These patients had median HbA1c levels 1.1% lower than patients diagnosed after reporting symptoms, a clinically and statistically significant difference (P = 0.01).