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Continuity of care aids depression diagnosis

By Lilian Anekwe

GP diagnosis of depression is seriously unreliable in the first consultation with a patient, but gets much better the more times assessments are carried out, a major analysis in The Lancet concludes.

The study appears to provide direct clinical benefits for continuity of care, with follow-up appointments reducing the diagnostic error rate by more than half.

A meta-analysis of 41 international primary care-based trials of more than 50,000 patients with depression found GPs had a ‘diagnostic sensitivity' of 50% - meaning they identified only half of all genuine cases of depression.

Some 47% of all patients diagnosed with depression by UK GPs genuinely had the illness, while 73% of patients in whom depression was ruled out were correctly reassured they did not have depression.

But those results got much better the more times GPs assessed patients before making a diagnosis. Inviting a patient back for a second consultation reduced the rate of error from 23% to 10%, with the researchers concluding a second assessment ‘allows re-examination of not just true positives, but also false positives'.

The study, led by psychiatrists at the Leicester General Hospital, also compared the accuracy of GP diagnosis in eight countries including the UK, the US, France, Spain and Italy.

Diagnostic accuracy varied from country to country, but UK GPs were poorest at diagnosing depression accurately – at 45% accuracy compared with the 83% achieved by Italian GPs.

The sensitivity and specificity found in UK trials was significantly lower than that seen overall – at 50% and 81% respectively.

Study leader Dr Alex Mitchell, consultant psychiatrist at the Leicester General Hospital, said: ‘Our results should not be interpreted as a criticism of GPs for failing to diagnose depression, but rather a call for better understanding of the problems that non-specialists face. No data suggests GPs do worse than other non-psychiatric medical colleagues.

‘In primary care, time and resources are limited, and psychological or even structured self-help programmes are often not available.

‘Because one-off brief assessment only facilitate diagnosis of about half of those with depression, we suggest that additional consultation time should be available for those likely to have depression.'

Professor Helen Lester, professor of primary care mental health at the University of Manchester, said: ‘This is a really interesting paper which makes a lot of sense to practising GPs. As a profession we are particularly good at being able to rule out conditions [and] the study confirms this a real strength of primary care.'

Study findings

- The meta-analysis of 41 studies with 50,371 patients found GPs correctly identified depression in 47.3% of cases and recorded depression in their notes in 33.6%

- The researchers found for every 100 cases seen in primary care, here were 15 false positives, 10 missed cases and 10 correctly identified cases of depression

- The sensitivity of GP diagnoses was 50.1% and the specificity was 81.3%, with a positive predictive value of 42.0% and a negative predictive value of 85.8%

Source: Lancet 2009; 28 July early online publication

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